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D'Alfonso A, Micheli G, Camilloni G. rDNA transcription, replication and stability in Saccharomyces cerevisiae. Semin Cell Dev Biol 2024; 159-160:1-9. [PMID: 38244478 DOI: 10.1016/j.semcdb.2024.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 12/20/2023] [Accepted: 01/10/2024] [Indexed: 01/22/2024]
Abstract
The ribosomal DNA locus (rDNA) is central for the functioning of cells because it encodes ribosomal RNAs, key components of ribosomes, and also because of its links to fundamental metabolic processes, with significant impact on genome integrity and aging. The repetitive nature of the rDNA gene units forces the locus to maintain sequence homogeneity through recombination processes that are closely related to genomic stability. The co-presence of basic DNA transactions, such as replication, transcription by major RNA polymerases, and recombination, in a defined and restricted area of the genome is of particular relevance as it affects the stability of the rDNA locus by both direct and indirect mechanisms. This condition is well exemplified by the rDNA of Saccharomyces cerevisiae. In this review we summarize essential knowledge on how the complexity and overlap of different processes contribute to the control of rDNA and genomic stability in this model organism.
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Affiliation(s)
- Anna D'Alfonso
- Dipartimento di Biologia e Biotecnologie C. Darwin, Università degli studi di Roma, Sapienza, Rome, Italy
| | - Gioacchino Micheli
- Istituto di Biologia e Patologia Molecolari, Consiglio Nazionale delle Ricerche, Rome, Italy
| | - Giorgio Camilloni
- Dipartimento di Biologia e Biotecnologie C. Darwin, Università degli studi di Roma, Sapienza, Rome, Italy.
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2
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Bi S, Jiang X, Ji Q, Wang Z, Ren J, Wang S, Yu Y, Wang R, Liu Z, Liu J, Hu J, Sun G, Wu Z, Diao Z, Li J, Sun L, Izpisua Belmonte JC, Zhang W, Liu GH, Qu J. The sirtuin-associated human senescence program converges on the activation of placenta-specific gene PAPPA. Dev Cell 2024; 59:991-1009.e12. [PMID: 38484732 DOI: 10.1016/j.devcel.2024.02.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2023] [Revised: 09/15/2023] [Accepted: 02/20/2024] [Indexed: 04/25/2024]
Abstract
Sirtuins are pro-longevity genes with chromatin modulation potential, but how these properties are connected is not well understood. Here, we generated a panel of isogeneic human stem cell lines with SIRT1-SIRT7 knockouts and found that any sirtuin deficiency leads to accelerated cellular senescence. Through large-scale epigenomic analyses, we show how sirtuin deficiency alters genome organization and that genomic regions sensitive to sirtuin deficiency are preferentially enriched in active enhancers, thereby promoting interactions within topologically associated domains and the formation of de novo enhancer-promoter loops. In all sirtuin-deficient human stem cell lines, we found that chromatin contacts are rewired to promote aberrant activation of the placenta-specific gene PAPPA, which controls the pro-senescence effects associated with sirtuin deficiency and serves as a potential aging biomarker. Based on our survey of the 3D chromatin architecture, we established connections between sirtuins and potential target genes, thereby informing the development of strategies for aging interventions.
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Affiliation(s)
- Shijia Bi
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaoyu Jiang
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Qianzhao Ji
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zehua Wang
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jie Ren
- CAS Key Laboratory of Genomic and Precision Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences and China National Center for Bioinformation, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China; Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing 100101, China; Key Laboratory of RNA Science and Engineering, Beijing Institute of Genomics, Chinese Academy of Sciences and China National Center for Bioinformation, Beijing 100101, China
| | - Si Wang
- Advanced Innovation Center for Human Brain Protection and National Clinical Research Center for Geriatric Disorders, Xuanwu Hospital Capital Medical University, Beijing 100053, China; Aging Translational Medicine Center, International Center for Aging and Cancer, Beijing Municipal Geriatric Medical Research Center, Xuanwu Hospital, Capital Medical University, Beijing 100053, China; The Fifth People's Hospital of Chongqing, Chongqing 400062, China
| | - Yang Yu
- Department of Obstetrics and Gynecology, Center for Reproductive Medicine, Peking University Third Hospital, Beijing 100191, China
| | - Ruoqi Wang
- University of Chinese Academy of Sciences, Beijing 100049, China; National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Zunpeng Liu
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Junhang Liu
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jianli Hu
- CAS Key Laboratory of Genomic and Precision Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences and China National Center for Bioinformation, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Guoqiang Sun
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zeming Wu
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing 100101, China; Beijing Institute for Stem Cell and Regenerative Medicine, Beijing 100101, China
| | - Zhiqing Diao
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jingyi Li
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China; Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing 100101, China; Beijing Institute for Stem Cell and Regenerative Medicine, Beijing 100101, China
| | - Liang Sun
- NHC Beijing Institute of Geriatrics, NHC Key Laboratory of Geriatrics, Institute of Geriatric Medicine of Chinese Academy of Medical Sciences, National Center of Gerontology/Beijing Hospital, Beijing 100730, China; Department of Clinical Laboratory, the First Affiliated Hospital of Kunming Medical University, Kunming 650032, China
| | | | - Weiqi Zhang
- CAS Key Laboratory of Genomic and Precision Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences and China National Center for Bioinformation, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China; Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing 100101, China; Aging Biomarker Consortium, Beijing 100101, China.
| | - Guang-Hui Liu
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China; Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing 100101, China; Beijing Institute for Stem Cell and Regenerative Medicine, Beijing 100101, China; Advanced Innovation Center for Human Brain Protection and National Clinical Research Center for Geriatric Disorders, Xuanwu Hospital Capital Medical University, Beijing 100053, China; Aging Translational Medicine Center, International Center for Aging and Cancer, Beijing Municipal Geriatric Medical Research Center, Xuanwu Hospital, Capital Medical University, Beijing 100053, China; Aging Biomarker Consortium, Beijing 100101, China.
| | - Jing Qu
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; Key Laboratory of Organ Regeneration and Reconstruction, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China; Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing 100101, China; Beijing Institute for Stem Cell and Regenerative Medicine, Beijing 100101, China; Aging Biomarker Consortium, Beijing 100101, China.
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3
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Yague-Sanz C. Shaping the chromatin landscape at rRNA and tRNA genes, an emerging new role for RNA polymerase II transcription? Yeast 2024; 41:135-147. [PMID: 38126234 DOI: 10.1002/yea.3921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Revised: 11/17/2023] [Accepted: 12/08/2023] [Indexed: 12/23/2023] Open
Abstract
Eukaryotic genes must be condensed into chromatin while remaining accessible to the transcriptional machinery to support gene expression. Among the three eukaryotic RNA polymerases (RNAP), RNAPII is unique, partly because of the C-terminal domain (CTD) of its largest subunit, Rpb1. Rpb1 CTD can be extensively modified during the transcription cycle, allowing for the co-transcriptional recruitment of specific interacting proteins. These include chromatin remodeling factors that control the opening or closing of chromatin. How the CTD-less RNAPI and RNAPIII deal with chromatin at rRNA and tRNA genes is less understood. Here, we review recent advances in our understanding of how the chromatin at tRNA genes and rRNA genes can be remodeled in response to environmental cues in yeast, with a particular focus on the role of local RNAPII transcription in recruiting chromatin remodelers at these loci. In fission yeast, RNAPII transcription at tRNA genes is important to re-establish a chromatin environment permissive to tRNA transcription, which supports growth from stationary phase. In contrast, local RNAPII transcription at rRNA genes correlates with the closing of the chromatin in starvation in budding and fission yeast, suggesting a role in establishing silent chromatin. These opposite roles might support a general model where RNAPII transcription recruits chromatin remodelers to tRNA and rRNA genes to promote the closing and reopening of chromatin in response to the environment.
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Affiliation(s)
- Carlo Yague-Sanz
- Damien Hermand's Laboratory, URPhyM-GEMO, The University of Namur, Namur, Belgium
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4
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Ayano T, Yokosawa T, Oki M. GTP-dependent regulation of heterochromatin fluctuations at subtelomeric regions in Saccharomyces cerevisiae. Genes Cells 2024; 29:217-230. [PMID: 38229233 DOI: 10.1111/gtc.13094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 12/13/2023] [Accepted: 12/22/2023] [Indexed: 01/18/2024]
Abstract
In eukaryotes, single cells in a population display different transcriptional profiles. One of the factors regulating this heterogeneity is the chromatin state in each cell. However, the mechanisms of epigenetic chromatin regulation of specific chromosomal regions remain unclear. Therefore, we used single-cell tracking system to analyze IMD2. IMD2 is located at the subtelomeric region of budding yeast, and its expression is epigenetically regulated by heterochromatin fluctuations. Treatment with mycophenolic acid, an inhibitor of de novo GTP biosynthesis, triggered a decrease in GTP, which caused heterochromatin fluctuations at the IMD2 locus. Interestingly, within individually tracked cells, IMD2 expression state underwent repeated switches even though IMD2 is positioned within the heterochromatin region. We also found that 30% of the cells in a population always expressed IMD2. Furthermore, the addition of nicotinamide, a histone deacetylase inhibitor, or guanine, the GTP biosynthesis factor in salvage pathway of GTP biosynthesis, regulated heterogeneity, resulting in IMD2 expression being uniformly induced or suppressed in the population. These results suggest that gene expression heterogeneity in the IMD2 region is regulated by changes in chromatin structure triggered by slight decreases in GTP.
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Affiliation(s)
- Takahito Ayano
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, Fukui, Japan
- Research Fellowships of Japan Society for the Promotion of Science for Young Scientists (JSPS), Tokyo, Japan
| | - Takuma Yokosawa
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, Fukui, Japan
| | - Masaya Oki
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, Fukui, Japan
- Life Science Innovation Center, University of Fukui, Fukui, Japan
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5
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Wang W, Zhang X, Garcia S, Leitch AR, Kovařík A. Intragenomic rDNA variation - the product of concerted evolution, mutation, or something in between? Heredity (Edinb) 2023; 131:179-188. [PMID: 37402824 PMCID: PMC10462631 DOI: 10.1038/s41437-023-00634-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 06/12/2023] [Accepted: 06/12/2023] [Indexed: 07/06/2023] Open
Abstract
The classical model of concerted evolution states that hundreds to thousands of ribosomal DNA (rDNA) units undergo homogenization, making the multiple copies of the individual units more uniform across the genome than would be expected given mutation frequencies and gene redundancy. While the universality of this over 50-year-old model has been confirmed in a range of organisms, advanced high throughput sequencing techniques have also revealed that rDNA homogenization in many organisms is partial and, in rare cases, even apparently failing. The potential underpinning processes leading to unexpected intragenomic variation have been discussed in a number of studies, but a comprehensive understanding remains to be determined. In this work, we summarize information on variation or polymorphisms in rDNAs across a wide range of taxa amongst animals, fungi, plants, and protists. We discuss the definition and description of concerted evolution and describe whether incomplete concerted evolution of rDNAs predominantly affects coding or non-coding regions of rDNA units and if it leads to the formation of pseudogenes or not. We also discuss the factors contributing to rDNA variation, such as interspecific hybridization, meiotic cycles, rDNA expression status, genome size, and the activity of effector genes involved in genetic recombination, epigenetic modifications, and DNA editing. Finally, we argue that a combination of approaches is needed to target genetic and epigenetic phenomena influencing incomplete concerted evolution, to give a comprehensive understanding of the evolution and functional consequences of intragenomic variation in rDNA.
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Affiliation(s)
- Wencai Wang
- Science and Technology Innovation Center, Guangzhou University of Chinese Medicine, Guangzhou, 510405, China
| | - Xianzhi Zhang
- Department of Horticulture, College of Horticulture and Landscape Architecture, Zhongkai University of Agriculture and Engineering, Guangzhou, 510225, China
| | - Sònia Garcia
- Institut Botànic de Barcelona, IBB (CSIC - Ajuntament de Barcelona), Barcelona, Spain
| | - Andrew R Leitch
- School of Biological and Behavioral Sciences, Queen Mary University of London, London, E1 4NS, UK
| | - Aleš Kovařík
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, CZ-61200, Czech Republic.
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6
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Zylstra A, Hadj-Moussa H, Horkai D, Whale AJ, Piguet B, Houseley J. Senescence in yeast is associated with amplified linear fragments of chromosome XII rather than ribosomal DNA circle accumulation. PLoS Biol 2023; 21:e3002250. [PMID: 37643194 PMCID: PMC10464983 DOI: 10.1371/journal.pbio.3002250] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 07/12/2023] [Indexed: 08/31/2023] Open
Abstract
The massive accumulation of extrachromosomal ribosomal DNA circles (ERCs) in yeast mother cells has been long cited as the primary driver of replicative ageing. ERCs arise through ribosomal DNA (rDNA) recombination, and a wealth of genetic data connects rDNA instability events giving rise to ERCs with shortened life span and other ageing pathologies. However, we understand little about the molecular effects of ERC accumulation. Here, we studied ageing in the presence and absence of ERCs, and unexpectedly found no evidence of gene expression differences that might indicate stress responses or metabolic feedback caused by ERCs. Neither did we observe any global change in the widespread disruption of gene expression that accompanies yeast ageing, altogether suggesting that ERCs are largely inert. Much of the differential gene expression that accompanies ageing in yeast was actually associated with markers of the senescence entry point (SEP), showing that senescence, rather than age, underlies these changes. Cells passed the SEP irrespective of ERCs, but we found the SEP to be associated with copy number amplification of a region of chromosome XII between the rDNA and the telomere (ChrXIIr) forming linear fragments up to approximately 1.8 Mb size, which arise in aged cells due to rDNA instability but through a different mechanism to ERCs. Therefore, although rDNA copy number increases dramatically with age due to ERC accumulation, our findings implicate ChrXIIr, rather than ERCs, as the primary driver of senescence during budding yeast ageing.
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Affiliation(s)
- Andre Zylstra
- Epigenetics Programme, Babraham Institute, Cambridge, United Kingdom
| | | | - Dorottya Horkai
- Epigenetics Programme, Babraham Institute, Cambridge, United Kingdom
| | - Alex J. Whale
- Epigenetics Programme, Babraham Institute, Cambridge, United Kingdom
| | - Baptiste Piguet
- Epigenetics Programme, Babraham Institute, Cambridge, United Kingdom
| | - Jonathan Houseley
- Epigenetics Programme, Babraham Institute, Cambridge, United Kingdom
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7
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Horkai D, Hadj-Moussa H, Whale AJ, Houseley J. Dietary change without caloric restriction maintains a youthful profile in ageing yeast. PLoS Biol 2023; 21:e3002245. [PMID: 37643155 PMCID: PMC10464975 DOI: 10.1371/journal.pbio.3002245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 07/12/2023] [Indexed: 08/31/2023] Open
Abstract
Caloric restriction increases lifespan and improves ageing health, but it is unknown whether these outcomes can be separated or achieved through less severe interventions. Here, we show that an unrestricted galactose diet in early life minimises change during replicative ageing in budding yeast, irrespective of diet later in life. Average mother cell division rate is comparable between glucose and galactose diets, and lifespan is shorter on galactose, but markers of senescence and the progressive dysregulation of gene expression observed on glucose are minimal on galactose, showing that these are not intrinsic aspects of replicative ageing but rather associated processes. Respiration on galactose is critical for minimising hallmarks of ageing, and forced respiration during ageing on glucose by overexpression of the mitochondrial biogenesis factor Hap4 also has the same effect though only in a fraction of cells. This fraction maintains Hap4 activity to advanced age with low senescence and a youthful gene expression profile, whereas other cells in the same population lose Hap4 activity, undergo dramatic dysregulation of gene expression and accumulate fragments of chromosome XII (ChrXIIr), which are tightly associated with senescence. Our findings support the existence of two separable ageing trajectories in yeast. We propose that a complete shift to the healthy ageing mode can be achieved in wild-type cells through dietary change in early life without caloric restriction.
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Affiliation(s)
- Dorottya Horkai
- Epigenetics Programme, Babraham Institute, Cambridge, United Kingdom
| | | | - Alex J. Whale
- Epigenetics Programme, Babraham Institute, Cambridge, United Kingdom
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8
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Sosa Ponce ML, Remedios MH, Moradi-Fard S, Cobb JA, Zaremberg V. SIR telomere silencing depends on nuclear envelope lipids and modulates sensitivity to a lysolipid. J Cell Biol 2023; 222:e202206061. [PMID: 37042812 PMCID: PMC10103788 DOI: 10.1083/jcb.202206061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 11/29/2022] [Accepted: 03/24/2023] [Indexed: 04/13/2023] Open
Abstract
The nuclear envelope (NE) is important in maintaining genome organization. The role of lipids in communication between the NE and telomere regulation was investigated, including how changes in lipid composition impact gene expression and overall nuclear architecture. Yeast was treated with the non-metabolizable lysophosphatidylcholine analog edelfosine, known to accumulate at the perinuclear ER. Edelfosine induced NE deformation and disrupted telomere clustering but not anchoring. Additionally, the association of Sir4 at telomeres decreased. RNA-seq analysis showed altered expression of Sir-dependent genes located at sub-telomeric (0-10 kb) regions, consistent with Sir4 dispersion. Transcriptomic analysis revealed that two lipid metabolic circuits were activated in response to edelfosine, one mediated by the membrane sensing transcription factors, Spt23/Mga2, and the other by a transcriptional repressor, Opi1. Activation of these transcriptional programs resulted in higher levels of unsaturated fatty acids and the formation of nuclear lipid droplets. Interestingly, cells lacking Sir proteins displayed resistance to unsaturated-fatty acids and edelfosine, and this phenotype was connected to Rap1.
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Affiliation(s)
| | | | - Sarah Moradi-Fard
- Departments of Biochemistry and Molecular Biology and Oncology, Cumming School of Medicine, Robson DNA Science Centre, Arnie Charbonneau Cancer Institute, Calgary, Canada
| | - Jennifer A. Cobb
- Departments of Biochemistry and Molecular Biology and Oncology, Cumming School of Medicine, Robson DNA Science Centre, Arnie Charbonneau Cancer Institute, Calgary, Canada
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada
| | - Vanina Zaremberg
- Department of Biological Sciences, University of Calgary, Calgary, Canada
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9
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Kwan EX, Alvino GM, Lynch KL, Levan PF, Amemiya HM, Wang XS, Johnson SA, Sanchez JC, Miller MA, Croy M, Lee SB, Naushab M, Bedalov A, Cuperus JT, Brewer BJ, Queitsch C, Raghuraman MK. Ribosomal DNA replication time coordinates completion of genome replication and anaphase in yeast. Cell Rep 2023; 42:112161. [PMID: 36842087 PMCID: PMC10142053 DOI: 10.1016/j.celrep.2023.112161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 12/19/2022] [Accepted: 02/09/2023] [Indexed: 02/27/2023] Open
Abstract
Timely completion of genome replication is a prerequisite for mitosis, genome integrity, and cell survival. A challenge to this timely completion comes from the need to replicate the hundreds of untranscribed copies of rDNA that organisms maintain in addition to the copies required for ribosome biogenesis. Replication of these rDNA arrays is relegated to late S phase despite their large size, repetitive nature, and essentiality. Here, we show that, in Saccharomyces cerevisiae, reducing the number of rDNA repeats leads to early rDNA replication, which results in delaying replication elsewhere in the genome. Moreover, cells with early-replicating rDNA arrays and delayed genome-wide replication aberrantly release the mitotic phosphatase Cdc14 from the nucleolus and enter anaphase prematurely. We propose that rDNA copy number determines the replication time of the rDNA locus and that the release of Cdc14 upon completion of rDNA replication is a signal for cell cycle progression.
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Affiliation(s)
- Elizabeth X Kwan
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Gina M Alvino
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Kelsey L Lynch
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Paula F Levan
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Haley M Amemiya
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Xiaobin S Wang
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Sarah A Johnson
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Joseph C Sanchez
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Madison A Miller
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Mackenzie Croy
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Seung-Been Lee
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Maria Naushab
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Antonio Bedalov
- Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Josh T Cuperus
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Bonita J Brewer
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Christine Queitsch
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA.
| | - M K Raghuraman
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA.
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10
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Paxman J, Zhou Z, O'Laughlin R, Liu Y, Li Y, Tian W, Su H, Jiang Y, Holness SE, Stasiowski E, Tsimring LS, Pillus L, Hasty J, Hao N. Age-dependent aggregation of ribosomal RNA-binding proteins links deterioration in chromatin stability with challenges to proteostasis. eLife 2022; 11:e75978. [PMID: 36194205 PMCID: PMC9578700 DOI: 10.7554/elife.75978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 10/03/2022] [Indexed: 11/13/2022] Open
Abstract
Chromatin instability and protein homeostasis (proteostasis) stress are two well-established hallmarks of aging, which have been considered largely independent of each other. Using microfluidics and single-cell imaging approaches, we observed that, during the replicative aging of Saccharomyces cerevisiae, a challenge to proteostasis occurs specifically in the fraction of cells with decreased stability within the ribosomal DNA (rDNA). A screen of 170 yeast RNA-binding proteins identified ribosomal RNA (rRNA)-binding proteins as the most enriched group that aggregate upon a decrease in rDNA stability induced by inhibition of a conserved lysine deacetylase Sir2. Further, loss of rDNA stability induces age-dependent aggregation of rRNA-binding proteins through aberrant overproduction of rRNAs. These aggregates contribute to age-induced proteostasis decline and limit cellular lifespan. Our findings reveal a mechanism underlying the interconnection between chromatin instability and proteostasis stress and highlight the importance of cell-to-cell variability in aging processes.
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Affiliation(s)
- Julie Paxman
- Department of Molecular Biology, Division of Biological Sciences, University of California, San DiegoLa JollaUnited States
| | - Zhen Zhou
- Department of Molecular Biology, Division of Biological Sciences, University of California, San DiegoLa JollaUnited States
| | - Richard O'Laughlin
- Department of Bioengineering, University of California, San DiegoLa JollaUnited States
| | - Yuting Liu
- Department of Molecular Biology, Division of Biological Sciences, University of California, San DiegoLa JollaUnited States
| | - Yang Li
- Department of Molecular Biology, Division of Biological Sciences, University of California, San DiegoLa JollaUnited States
| | - Wanying Tian
- Department of Molecular Biology, Division of Biological Sciences, University of California, San DiegoLa JollaUnited States
| | - Hetian Su
- Department of Molecular Biology, Division of Biological Sciences, University of California, San DiegoLa JollaUnited States
| | - Yanfei Jiang
- Department of Molecular Biology, Division of Biological Sciences, University of California, San DiegoLa JollaUnited States
| | - Shayna E Holness
- Department of Chemistry and Biochemistry, University of California, San DiegoLa JollaUnited States
| | - Elizabeth Stasiowski
- Department of Bioengineering, University of California, San DiegoLa JollaUnited States
| | - Lev S Tsimring
- Synthetic Biology Institute, University of California, San DiegoLa JollaUnited States
| | - Lorraine Pillus
- Department of Molecular Biology, Division of Biological Sciences, University of California, San DiegoLa JollaUnited States
- UCSD Moores Cancer Center, University of California San, DiegoLa JollaUnited States
| | - Jeff Hasty
- Department of Molecular Biology, Division of Biological Sciences, University of California, San DiegoLa JollaUnited States
- Department of Bioengineering, University of California, San DiegoLa JollaUnited States
- Synthetic Biology Institute, University of California, San DiegoLa JollaUnited States
| | - Nan Hao
- Department of Molecular Biology, Division of Biological Sciences, University of California, San DiegoLa JollaUnited States
- Department of Bioengineering, University of California, San DiegoLa JollaUnited States
- Synthetic Biology Institute, University of California, San DiegoLa JollaUnited States
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11
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Bauer SL, Grochalski TNT, Smialowska A, Åström SU. Sir2 and Reb1 antagonistically regulate nucleosome occupancy in subtelomeric X-elements and repress TERRAs by distinct mechanisms. PLoS Genet 2022; 18:e1010419. [PMID: 36137093 PMCID: PMC9531808 DOI: 10.1371/journal.pgen.1010419] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 10/04/2022] [Accepted: 09/08/2022] [Indexed: 11/19/2022] Open
Abstract
Telomere chromatin structure is pivotal for maintaining genome stability by regulating the binding of telomere-associated proteins and inhibiting the DNA damage response. In Saccharomyces cerevisiae, silent information regulator (Sir) proteins bind to terminal repeats and to subtelomeric X-elements, resulting in transcriptional silencing. Herein, we show that sir2 mutant strains display a specific loss of a nucleosome residing in the X-elements and that this deficiency is remarkably consistent between different telomeres. The X-elements contain several binding sites for the transcription factor Reb1 and we found that Sir2 and Reb1 compete for stabilizing/destabilizing this nucleosome, i.e. inactivation of Reb1 in a sir2 background reinstated the lost nucleosome. The telomeric-repeat-containing RNAs (TERRAs) originate from subtelomeric regions and extend into the terminal repeats. Both Sir2 and Reb1 repress TERRAs and in a sir2 reb1 double mutant, TERRA levels increased synergistically, showing that Sir2 and Reb1 act in different pathways for repressing TERRAs. We present evidence that Reb1 restricts TERRAs by terminating transcription. Mapping the 5′-ends of TERRAs from several telomeres revealed that the Sir2-stabilized nucleosome is the first nucleosome downstream from the transcriptional start site for TERRAs. Finally, moving an X-element to a euchromatic locus changed nucleosome occupancy and positioning, demonstrating that X-element nucleosome structure is dependent on the local telomere environment. Telomeres are specialized structures at the end of linear chromosomes that protect the genetic material from degradation and mistaken recognition as sites of damage. Telomere dysfunction has been linked to several diseases and senescence. The telomeres contain repetitive DNA sequences bound by specialized proteins. Here, we describe two such proteins, Sir2 and Reb1, which regulate the formation of nucleosomes at a repetitive sequence known as the X-element. Sir2 has very important roles in regulating the accessibility of telomeres to the cellular machinery that reads and transcribes the genetic material. Reb1 had not been previously implicated in telomere biology, but is rather known as a general regulator of transcription. We explored the effects of removing either or both of these factors on telomeric features and their relationship in regulating the structure and accessibility of the telomeres in budding yeast. We show that Sir2 and Reb1 have opposing roles in stabilizing and de-stabilizing a nucleosome at the telomeres, but that both inhibit the accumulation of a non-coding RNA molecule transcribed from the telomeres.
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Affiliation(s)
- Stefanie L. Bauer
- Department of Molecular Biosciences, the Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Thomas N. T. Grochalski
- Department of Molecular Biosciences, the Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Agata Smialowska
- National Bioinformatics Infrastructure Sweden, Science for Life Laboratory, Stockholm University, Stockholm, Sweden
| | - Stefan U. Åström
- Department of Molecular Biosciences, the Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
- * E-mail:
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12
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Fagerli E, Escobar I, Ferrier FJ, Jackson CW, Perez-Lao EJ, Perez-Pinzon MA. Sirtuins and cognition: implications for learning and memory in neurological disorders. Front Physiol 2022; 13:908689. [PMID: 35936890 PMCID: PMC9355297 DOI: 10.3389/fphys.2022.908689] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 06/30/2022] [Indexed: 11/18/2022] Open
Abstract
Sirtuins are an evolutionarily conserved family of regulatory proteins that function in an NAD+ -dependent manner. The mammalian family of sirtuins is composed of seven histone deacetylase and ADP-ribosyltransferase proteins (SIRT1-SIRT7) that are found throughout the different cellular compartments of the cell. Sirtuins in the brain have received considerable attention in cognition due to their role in a plethora of metabolic and age-related diseases and their ability to induce neuroprotection. More recently, sirtuins have been shown to play a role in normal physiological cognitive function, and aberrant sirtuin function is seen in pathological cellular states. Sirtuins are believed to play a role in cognition through enhancing synaptic plasticity, influencing epigenetic regulation, and playing key roles in molecular pathways involved with oxidative stress affecting mitochondrial function. This review aims to discuss recent advances in the understanding of the role of mammalian sirtuins in cognitive function and the therapeutic potential of targeting sirtuins to ameliorate cognitive deficits in neurological disorders.
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Affiliation(s)
| | | | | | | | | | - Miguel A. Perez-Pinzon
- Department of Neurology, Miller School of Medicine, University of Miami, Miami, FL, United States
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13
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Zhao G, Rusche LN. Sirtuins in Epigenetic Silencing and Control of Gene Expression in Model and Pathogenic Fungi. Annu Rev Microbiol 2022; 76:157-178. [PMID: 35609947 DOI: 10.1146/annurev-micro-041020-100926] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Fungi, including yeasts, molds, and mushrooms, proliferate on decaying matter and then adopt quiescent forms once nutrients are depleted. This review explores how fungi use sirtuin deacetylases to sense and respond appropriately to changing nutrients. Because sirtuins are NAD+-dependent deacetylases, their activity is sensitive to intracellular NAD+ availability. This allows them to transmit information about a cell's metabolic state on to the biological processes they influence. Fungal sirtuins are primarily known to deacetylate histones, repressing transcription and modulating genome stability. Their target genes include those involved in NAD+ homeostasis, metabolism, sporulation, secondary metabolite production, and virulence traits of pathogenic fungi. By targeting different genes over evolutionary time, sirtuins serve as rewiring points that allow organisms to evolve novel responses to low NAD+ stress by bringing relevant biological processes under the control of sirtuins. Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Guolei Zhao
- Department of Biological Sciences, University at Buffalo, The State University of New York, Buffalo, New York, USA; ,
| | - Laura N Rusche
- Department of Biological Sciences, University at Buffalo, The State University of New York, Buffalo, New York, USA; ,
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14
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Ding Q, Li R, Ren X, Chan LY, Ho VWS, Xie D, Ye P, Zhao Z. Genomic architecture of 5S rDNA cluster and its variations within and between species. BMC Genomics 2022; 23:238. [PMID: 35346033 PMCID: PMC8961926 DOI: 10.1186/s12864-022-08476-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Accepted: 03/16/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Ribosomal DNAs (rDNAs) are arranged in purely tandem repeats, preventing them from being reliably assembled onto chromosomes during generation of genome assembly. The uncertainty of rDNA genomic structure presents a significant barrier for studying their function and evolution. RESULTS Here we generate ultra-long Oxford Nanopore Technologies (ONT) and short NGS reads to delineate the architecture and variation of the 5S rDNA cluster in the different strains of C. elegans and C. briggsae. We classify the individual rDNA's repeating units into 25 types based on the unique sequence variations in each unit of C. elegans (N2). We next perform assembly of the cluster by taking advantage of the long reads that carry these units, which led to an assembly of 5S rDNA cluster consisting of up to 167 consecutive 5S rDNA units in the N2 strain. The ordering and copy number of various rDNA units are consistent with the separation time between strains. Surprisingly, we observed a drastically reduced level of variation in the unit composition in the 5S rDNA cluster in the C. elegans CB4856 and C. briggsae AF16 strains than in the C. elegans N2 strain, suggesting that N2, a widely used reference strain, is likely to be defective in maintaining the 5S rDNA cluster stability compared with other wild isolates of C. elegans or C. briggsae. CONCLUSIONS The results demonstrate that Nanopore DNA sequencing reads are capable of generating assembly of highly repetitive sequences, and rDNA units are highly dynamic both within and between population(s) of the same species in terms of sequence and copy number. The detailed structure and variation of the 5S rDNA units within the rDNA cluster pave the way for functional and evolutionary studies.
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Affiliation(s)
- Qiutao Ding
- Department of Biology, Hong Kong Baptist University, Hong Kong SAR, China
| | - Runsheng Li
- Department of Biology, Hong Kong Baptist University, Hong Kong SAR, China
- Department of Infectious Diseases and Public Health, City University of Hong Kong, Hong Kong SAR, China
| | - Xiaoliang Ren
- Department of Biology, Hong Kong Baptist University, Hong Kong SAR, China
| | - Lu-Yan Chan
- Department of Biology, Hong Kong Baptist University, Hong Kong SAR, China
| | - Vincy W S Ho
- Department of Biology, Hong Kong Baptist University, Hong Kong SAR, China
| | - Dongying Xie
- Department of Biology, Hong Kong Baptist University, Hong Kong SAR, China
| | - Pohao Ye
- Department of Biology, Hong Kong Baptist University, Hong Kong SAR, China
| | - Zhongying Zhao
- Department of Biology, Hong Kong Baptist University, Hong Kong SAR, China.
- State Key Laboratory of Environmental and Biological Analysis, Hong Kong Baptist University, Hong Kong SAR, China.
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15
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Commuting to Work: Nucleolar Long Non-Coding RNA Control Ribosome Biogenesis from Near and Far. Noncoding RNA 2021; 7:ncrna7030042. [PMID: 34287370 PMCID: PMC8293466 DOI: 10.3390/ncrna7030042] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 07/09/2021] [Accepted: 07/11/2021] [Indexed: 12/26/2022] Open
Abstract
Gene expression is an essential process for cellular growth, proliferation, and differentiation. The transcription of protein-coding genes and non-coding loci depends on RNA polymerases. Interestingly, numerous loci encode long non-coding (lnc)RNA transcripts that are transcribed by RNA polymerase II (RNAPII) and fine-tune the RNA metabolism. The nucleolus is a prime example of how different lncRNA species concomitantly regulate gene expression by facilitating the production and processing of ribosomal (r)RNA for ribosome biogenesis. Here, we summarise the current findings on how RNAPII influences nucleolar structure and function. We describe how RNAPII-dependent lncRNA can both promote nucleolar integrity and inhibit ribosomal (r)RNA synthesis by modulating the availability of rRNA synthesis factors in trans. Surprisingly, some lncRNA transcripts can directly originate from nucleolar loci and function in cis. The nucleolar intergenic spacer (IGS), for example, encodes nucleolar transcripts that counteract spurious rRNA synthesis in unperturbed cells. In response to DNA damage, RNAPII-dependent lncRNA originates directly at broken ribosomal (r)DNA loci and is processed into small ncRNA, possibly to modulate DNA repair. Thus, lncRNA-mediated regulation of nucleolar biology occurs by several modes of action and is more direct than anticipated, pointing to an intimate crosstalk of RNA metabolic events.
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16
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Moradi‐Fard S, Mojumdar A, Chan M, Harkness TA, Cobb JA. Smc5/6 in the rDNA modulates lifespan independently of Fob1. Aging Cell 2021; 20:e13373. [PMID: 33979898 PMCID: PMC8208791 DOI: 10.1111/acel.13373] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 03/18/2021] [Accepted: 04/08/2021] [Indexed: 12/28/2022] Open
Abstract
The ribosomal DNA (rDNA) in Saccharomycescerevisiae is in one tandem repeat array on Chromosome XII. Two regions within each repetitive element, called intergenic spacer 1 (IGS1) and IGS2, are important for organizing the rDNA within the nucleolus. The Smc5/6 complex localizes to IGS1 and IGS2. We show that Smc5/6 has a function in the rDNA beyond its role in homologous recombination (HR) at the replication fork barrier (RFB) located in IGS1. Fob1 is required for optimal binding of Smc5/6 at IGS1 whereas the canonical silencing factor Sir2 is required for its optimal binding at IGS2, independently of Fob1. Through interdependent interactions, Smc5/6 stabilizes Sir2 and Cohibin at both IGS and its recovery at IGS2 is important for nucleolar compaction and transcriptional silencing, which in turn supports rDNA stability and lifespan.
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Affiliation(s)
- Sarah Moradi‐Fard
- Departments of Biochemistry & Molecular Biology and Oncology Robson DNA Science Centre Arnie Charbonneau Cancer Institute Cumming School of Medicine University of Calgary Calgary AB Canada
| | - Aditya Mojumdar
- Departments of Biochemistry & Molecular Biology and Oncology Robson DNA Science Centre Arnie Charbonneau Cancer Institute Cumming School of Medicine University of Calgary Calgary AB Canada
| | - Megan Chan
- Departments of Biochemistry & Molecular Biology and Oncology Robson DNA Science Centre Arnie Charbonneau Cancer Institute Cumming School of Medicine University of Calgary Calgary AB Canada
| | - Troy A.A. Harkness
- Department of Biochemistry, Microbiology and Immunology University of Saskatchewan Saskatoon SK Canada
| | - Jennifer A. Cobb
- Departments of Biochemistry & Molecular Biology and Oncology Robson DNA Science Centre Arnie Charbonneau Cancer Institute Cumming School of Medicine University of Calgary Calgary AB Canada
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17
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Wang J, Zhang H, Xu S, Liu Z, Yang L, Fang L, Huo Z, Yan X. Characterization of the SIRT genes and their distinct expression patterns in Manila clams (Ruditapes philippinarum) exposed to air. Meta Gene 2021. [DOI: 10.1016/j.mgene.2021.100892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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18
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Larocca D, Lee J, West MD, Labat I, Sternberg H. No Time to Age: Uncoupling Aging from Chronological Time. Genes (Basel) 2021; 12:611. [PMID: 33919082 PMCID: PMC8143125 DOI: 10.3390/genes12050611] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 04/13/2021] [Accepted: 04/16/2021] [Indexed: 12/20/2022] Open
Abstract
Multicellular life evolved from simple unicellular organisms that could replicate indefinitely, being essentially ageless. At this point, life split into two fundamentally different cell types: the immortal germline representing an unbroken lineage of cell division with no intrinsic endpoint and the mortal soma, which ages and dies. In this review, we describe the germline as clock-free and the soma as clock-bound and discuss aging with respect to three DNA-based cellular clocks (telomeric, DNA methylation, and transposable element). The ticking of these clocks corresponds to the stepwise progressive limitation of growth and regeneration of somatic cells that we term somatic restriction. Somatic restriction acts in opposition to strategies that ensure continued germline replication and regeneration. We thus consider the plasticity of aging as a process not fixed to the pace of chronological time but one that can speed up or slow down depending on the rate of intrinsic cellular clocks. We further describe how germline factor reprogramming might be used to slow the rate of aging and potentially reverse it by causing the clocks to tick backward. Therefore, reprogramming may eventually lead to therapeutic strategies to treat degenerative diseases by altering aging itself, the one condition common to us all.
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Affiliation(s)
| | - Jieun Lee
- AgeX Therapeutics Inc., Alameda, CA 94501, USA; (J.L.); (M.D.W.); (I.L.); (H.S.)
| | - Michael D. West
- AgeX Therapeutics Inc., Alameda, CA 94501, USA; (J.L.); (M.D.W.); (I.L.); (H.S.)
| | - Ivan Labat
- AgeX Therapeutics Inc., Alameda, CA 94501, USA; (J.L.); (M.D.W.); (I.L.); (H.S.)
| | - Hal Sternberg
- AgeX Therapeutics Inc., Alameda, CA 94501, USA; (J.L.); (M.D.W.); (I.L.); (H.S.)
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19
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Cai Q, Tian L, Xie JT, Huang QY, Feng MG, Keyhani NO. A fungal sirtuin modulates development and virulence in the insect pathogen, Beauveria bassiana. Environ Microbiol 2021; 23:5164-5183. [PMID: 33817929 DOI: 10.1111/1462-2920.15497] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 03/25/2021] [Accepted: 03/30/2021] [Indexed: 01/02/2023]
Abstract
Chromatin transitions are mediated in part by acetylation/deacetylation post-translational modifications of histones. Histone deacetylases, e.g. sirtuins (Sir-proteins), repress transcription via promotion of heterochromatin formation. Here, we characterize the Sir2 class III histone deacetylase (BbSir2) in the environmentally and economically important fungal insect pathogen, Beauveria bassiana. BbSir2 is shown to contribute to the deacetylation of lysine residues on H3 and H4 histones. Targeted gene knockout of BbSir2 resulted in impaired asexual development, reduced abilities to utilize various carbon/nitrogen sources, reduced tolerance to oxidative, heat, and UV stress, and attenuated virulence. ΔBbSir2 cells showed disrupted cell cycle development and abnormal hyphal septation patterns. Proteomic protein acetylation analyses of wild type and ΔBbSir2 cells revealed the differential abundance of 462 proteins and altered (hyper- or hypo-) acetylation of 436 lysine residues on 350 proteins. Bioinformatic analyses revealed enrichment in pathways involved in carbon/nitrogen metabolism, cell cycle control and cell rescue, defence and mitochondrial functioning. Critical targets involved in virulence included LysM effector proteins and a benzoquinone oxidoreductase implicated in detoxification of cuticular compounds. These data indicate broad effects of BbSir2 on fungal development and stress response, with identification of discrete targets that can account for the observed (decreased) virulence phenotype.
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Affiliation(s)
- Qing Cai
- State Key Laboratory of Agricultural Microbiology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, China.,Department of Microbiology and Cell Science, University of Florida, Bldg. 981, Museum Road, Gainesville, FL, 32611, USA
| | - Li Tian
- Shandong Provincial Key Laboratory of Microbial Engineering, Department of Bioengineering, Qilu University of Technology, Jinan, Shandong, 250353, China
| | - Jia-Tao Xie
- State Key Laboratory of Agricultural Microbiology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Qiu-Ying Huang
- State Key Laboratory of Agricultural Microbiology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Ming-Guang Feng
- Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Nemat O Keyhani
- Department of Microbiology and Cell Science, University of Florida, Bldg. 981, Museum Road, Gainesville, FL, 32611, USA
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20
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Thousands of high-quality sequencing samples fail to show meaningful correlation between 5S and 45S ribosomal DNA arrays in humans. Sci Rep 2021; 11:449. [PMID: 33432083 PMCID: PMC7801704 DOI: 10.1038/s41598-020-80049-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 12/15/2020] [Indexed: 11/08/2022] Open
Abstract
The ribosomal RNA genes (rDNA) are tandemly arrayed in most eukaryotes and exhibit vast copy number variation. There is growing interest in integrating this variation into genotype-phenotype associations. Here, we explored a possible association of rDNA copy number variation with autism spectrum disorder and found no difference between probands and unaffected siblings. Because short-read sequencing estimates of rDNA copy number are error prone, we sought to validate our 45S estimates. Previous studies reported tightly correlated, concerted copy number variation between the 45S and 5S arrays, which should enable the validation of 45S copy number estimates with pulsed-field gel-verified 5S copy numbers. Here, we show that the previously reported strong concerted copy number variation may be an artifact of variable data quality in the earlier published 1000 Genomes Project sequences. We failed to detect a meaningful correlation between 45S and 5S copy numbers in thousands of samples from the high-coverage Simons Simplex Collection dataset as well as in the recent high-coverage 1000 Genomes Project sequences. Our findings illustrate the challenge of genotyping repetitive DNA regions accurately and call into question the accuracy of recently published studies of rDNA copy number variation in cancer that relied on diverse publicly available resources for sequence data.
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21
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Hong S, Huh WK. Loss of Smi1, a protein involved in cell wall synthesis, extends replicative life span by enhancing rDNA stability in Saccharomyces cerevisiae. J Biol Chem 2021; 296:100258. [PMID: 33837734 PMCID: PMC7948926 DOI: 10.1016/j.jbc.2021.100258] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 12/14/2020] [Accepted: 01/04/2021] [Indexed: 11/17/2022] Open
Abstract
In Saccharomyces cerevisiae, replicative life span (RLS) is primarily affected by the stability of ribosomal DNA (rDNA). The stability of the highly repetitive rDNA array is maintained through transcriptional silencing by the NAD+-dependent histone deacetylase Sir2. Recently, the loss of Smi1, a protein of unknown molecular function that has been proposed to be involved in cell wall synthesis, has been demonstrated to extend RLS in S. cerevisiae, but the mechanism by which Smi1 regulates RLS has not been elucidated. In this study, we determined that the loss of Smi1 extends RLS in a Sir2-dependent manner. We observed that the smi1Δ mutation enhances transcriptional silencing at the rDNA locus and promotes rDNA stability. In the absence of Smi1, the stress-responsive transcription factor Msn2 translocates from the cytoplasm to the nucleus, and nuclear-accumulated Msn2 stimulates the expression of nicotinamidase Pnc1, which serves as an activator of Sir2. In addition, we observed that the MAP kinase Hog1 is activated in smi1Δ cells and that the activation of Hog1 induces the translocation of Msn2 into the nucleus. Taken together, our findings suggest that the loss of Smi1 leads to the nuclear accumulation of Msn2 and stimulates the expression of Pnc1, thereby enhancing Sir2-mediated rDNA stability and extending RLS in S. cerevisiae.
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Affiliation(s)
- Sujin Hong
- School of Biological Sciences, Seoul National University, Seoul, Republic of Korea
| | - Won-Ki Huh
- School of Biological Sciences, Seoul National University, Seoul, Republic of Korea; Institute of Microbiology, Seoul National University, Seoul, Republic of Korea.
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22
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Egidi A, Di Felice F, Camilloni G. Saccharomyces cerevisiae rDNA as super-hub: the region where replication, transcription and recombination meet. Cell Mol Life Sci 2020; 77:4787-4798. [PMID: 32476055 PMCID: PMC11104796 DOI: 10.1007/s00018-020-03562-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 05/04/2020] [Accepted: 05/25/2020] [Indexed: 11/29/2022]
Abstract
Saccharomyces cerevisiae ribosomal DNA, the repeated region where rRNAs are synthesized by about 150 encoding units, hosts all the protein machineries responsible for the main DNA transactions such as replication, transcription and recombination. This and its repetitive nature make rDNA a unique and complex genetic locus compared to any other. All the different molecular machineries acting in this locus need to be accurately and finely controlled and coordinated and for this reason rDNA is one of the most impressive examples of highly complex molecular regulated loci. The region in which the large molecular complexes involved in rDNA activity and/or regulation are recruited is extremely small: that is, the 2.5 kb long intergenic spacer, interrupting each 35S RNA coding unit from the next. All S. cerevisiae RNA polymerases (I, II and III) transcribing the different genetic rDNA elements are recruited here; a sequence responsible for each rDNA unit replication, which needs its molecular apparatus, also localizes here; moreover, it is noteworthy that the rDNA replication proceeds almost unidirectionally because each replication fork is stopped in the so-called replication fork barrier. These localized fork blocking events induce, with a given frequency, the homologous recombination process by which cells maintain a high identity among the rDNA repeated units. Here, we describe the different processes involving the rDNA locus, how they influence each other and how these mutual interferences are highly regulated and coordinated. We propose that an rDNA conformation as a super-hub could help in optimizing the micro-environment for all basic DNA transactions.
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Affiliation(s)
- Alessandra Egidi
- Dipartimento di Biologia e Biotecnologie, Università di Roma, Sapienza, Rome, Italy
| | - Francesca Di Felice
- Dipartimento di Biologia e Biotecnologie, Università di Roma, Sapienza, Rome, Italy
| | - Giorgio Camilloni
- Dipartimento di Biologia e Biotecnologie, Università di Roma, Sapienza, Rome, Italy.
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23
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Ma O, Le T, Talbott G, HoangThao Nguyen T, Ha D, Ho L. Sirt3 regulates adipogenesis and adipokine secretion via its enzymatic activity. Pharmacol Res Perspect 2020; 8:e00670. [PMID: 33191653 PMCID: PMC7667394 DOI: 10.1002/prp2.670] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 09/14/2020] [Accepted: 09/15/2020] [Indexed: 12/25/2022] Open
Abstract
The purpose of this research was to identify if Sirt3 plays a role in marrow adipogenesis and adipokines secretion, especially adiponectin using bone marrow-derived stroma (ST2) cell model. Sirt3 overexpression leads to a significant increase in adipogenesis compared to controls. The induction of adipogenesis by Sirt3 is associated with increased gene expression of adipocyte markers as well as adiponectin/adipokines. In sharp contrast, the inhibition of Sirt3 exhibited significantly decreased adipogenesis, adipocyte markers, and adiponectin/adipokines compared to the controls. Interestingly, perilipin 1 (Plin 1) expression was decreased in Sirt3 induction but increased in Sirt3 inhibition. One hundred and fifteen mitochondrial acetylated peptides from 67 mitochondrial proteins had lower levels of acetylation in adipocytes induced by Sirt3 overexpression (Sirt3OE) compared to the control. Of the 67 proteins less enriched in acetylation, 22 acetylated proteins were decreased by more than twofold. These proteins are considered potential Sirt3 substrates in adipogenesis. In conclusion, Sirt3 has a novel, important role in modulating adipogenesis and adiponectin/adipokine expression. The connection axis among Sirt3-adipogenesis-adipokines was linked to its substrates by mass spectrometry analysis. These findings contribute to the efforts of revealing Sirt3 functions and Sirt3 usage as a potential target for treatment of metabolic homeostasis and diseases including type 2 diabetes.
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Affiliation(s)
- Oanh Ma
- California Northstate University College of PharmacyElk GroveCAUSA
| | - Truc Le
- California Northstate University College of PharmacyElk GroveCAUSA
| | - George Talbott
- California Northstate University College of PharmacyElk GroveCAUSA
| | | | - Dorothy Ha
- California Northstate University College of PharmacyElk GroveCAUSA
| | - Linh Ho
- California Northstate University College of PharmacyElk GroveCAUSA
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24
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Klein MA, Denu JM. Biological and catalytic functions of sirtuin 6 as targets for small-molecule modulators. J Biol Chem 2020; 295:11021-11041. [PMID: 32518153 DOI: 10.1074/jbc.rev120.011438] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Revised: 06/08/2020] [Indexed: 12/14/2022] Open
Abstract
Sirtuin 6 (SIRT6) is a nuclear NAD+-dependent deacetylase of histone H3 that regulates genome stability and gene expression. However, nonhistone substrates and additional catalytic activities of SIRT6, including long-chain deacylation and mono-ADP-ribosylation of other proteins, have also been reported, but many of these noncanonical roles remain enigmatic. Genetic studies have revealed critical homeostatic cellular functions of SIRT6, underscoring the need to better understand which catalytic functions and molecular pathways are driving SIRT6-associated phenotypes. At the physiological level, SIRT6 activity promotes increased longevity by regulating metabolism and DNA repair. Recent work has identified natural products and synthetic small molecules capable of activating the inefficient in vitro deacetylase activity of SIRT6. Here, we discuss the cellular functions of SIRT6 with a focus on attributing its catalytic activity to its proposed biological functions. We cover the molecular architecture and catalytic mechanisms that distinguish SIRT6 from other NAD+-dependent deacylases. We propose that combining specific SIRT6 amino acid substitutions identified in enzymology studies and activity-selective compounds could help delineate SIRT6 functions in specific biological contexts and resolve the apparently conflicting roles of SIRT6 in processes such as tumor development. We further highlight the recent development of small-molecule modulators that provide additional biological insight into SIRT6 functions and offer therapeutic approaches to manage metabolic and age-associated diseases.
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Affiliation(s)
- Mark A Klein
- Wisconsin Institute for Discovery, University of Wisconsin, Madison, Wisconsin, USA.,Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, USA
| | - John M Denu
- Wisconsin Institute for Discovery, University of Wisconsin, Madison, Wisconsin, USA .,Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, USA
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25
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Shen D, Skibbens RV. Promotion of Hyperthermic-Induced rDNA Hypercondensation in Saccharomyces cerevisiae. Genetics 2020; 214:589-604. [PMID: 31980450 PMCID: PMC7054013 DOI: 10.1534/genetics.119.302994] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Accepted: 12/29/2019] [Indexed: 12/11/2022] Open
Abstract
Ribosome biogenesis is tightly regulated through stress-sensing pathways that impact genome stability, aging and senescence. In Saccharomyces cerevisiae, ribosomal RNAs are transcribed from rDNA located on the right arm of chromosome XII. Numerous studies reveal that rDNA decondenses into a puff-like structure during interphase, and condenses into a tight loop-like structure during mitosis. Intriguingly, a novel and additional mechanism of increased mitotic rDNA compaction (termed hypercondensation) was recently discovered that occurs in response to temperature stress (hyperthermic-induced) and is rapidly reversible. Here, we report that neither changes in condensin binding or release of DNA during mitosis, nor mutation of factors that regulate cohesin binding and release, appear to play a critical role in hyperthermic-induced rDNA hypercondensation. A candidate genetic approach revealed that deletion of either HSP82 or HSC82 (Hsp90 encoding heat shock paralogs) result in significantly reduced hyperthermic-induced rDNA hypercondensation. Intriguingly, Hsp inhibitors do not impact rDNA hypercondensation. In combination, these findings suggest that Hsp90 either stabilizes client proteins, which are sensitive to very transient thermic challenges, or directly promotes rDNA hypercondensation during preanaphase. Our findings further reveal that the high mobility group protein Hmo1 is a negative regulator of mitotic rDNA condensation, distinct from its role in promoting premature condensation of rDNA during interphase upon nutrient starvation.
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Affiliation(s)
- Donglai Shen
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania 18015
| | - Robert V Skibbens
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania 18015
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Genomic Considerations for the Modification of Saccharomyces cerevisiae for Biofuel and Metabolite Biosynthesis. Microorganisms 2020; 8:microorganisms8030321. [PMID: 32110897 PMCID: PMC7143498 DOI: 10.3390/microorganisms8030321] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 02/02/2020] [Accepted: 02/24/2020] [Indexed: 11/22/2022] Open
Abstract
The growing global population and developing world has put a strain on non-renewable natural resources, such as fuels. The shift to renewable sources will, thus, help meet demands, often through the modification of existing biosynthetic pathways or the introduction of novel pathways into non-native species. There are several useful biosynthetic pathways endogenous to organisms that are not conducive for the scale-up necessary for industrial use. The use of genetic and synthetic biological approaches to engineer these pathways in non-native organisms can help ameliorate these challenges. The budding yeast Saccharomyces cerevisiae offers several advantages for genetic engineering for this purpose due to its widespread use as a model system studied by many researchers. The focus of this review is to present a primer on understanding genomic considerations prior to genetic modification and manipulation of S. cerevisiae. The choice of a site for genetic manipulation can have broad implications on transcription throughout a region and this review will present the current understanding of position effects on transcription.
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Croft T, Venkatakrishnan P, Lin SJ. NAD + Metabolism and Regulation: Lessons From Yeast. Biomolecules 2020; 10:E330. [PMID: 32092906 PMCID: PMC7072712 DOI: 10.3390/biom10020330] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 02/15/2020] [Accepted: 02/16/2020] [Indexed: 12/13/2022] Open
Abstract
Nicotinamide adenine dinucleotide (NAD+) is an essential metabolite involved in various cellular processes. The cellular NAD+ pool is maintained by three biosynthesis pathways, which are largely conserved from bacteria to human. NAD+ metabolism is an emerging therapeutic target for several human disorders including diabetes, cancer, and neuron degeneration. Factors regulating NAD+ homeostasis have remained incompletely understood due to the dynamic nature and complexity of NAD+ metabolism. Recent studies using the genetically tractable budding yeast Saccharomyces cerevisiae have identified novel NAD+ homeostasis factors. These findings help provide a molecular basis for how may NAD+ and NAD+ homeostasis factors contribute to the maintenance and regulation of cellular function. Here we summarize major NAD+ biosynthesis pathways, selected cellular processes that closely connect with and contribute to NAD+ homeostasis, and regulation of NAD+ metabolism by nutrient-sensing signaling pathways. We also extend the discussions to include possible implications of NAD+ homeostasis factors in human disorders. Understanding the cross-regulation and interconnections of NAD+ precursors and associated cellular pathways will help elucidate the mechanisms of the complex regulation of NAD+ homeostasis. These studies may also contribute to the development of effective NAD+-based therapeutic strategies specific for different types of NAD+ deficiency related disorders.
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Affiliation(s)
| | | | - Su-Ju Lin
- Department of Microbiology and Molecular Genetics, College of Biological Sciences, University of California, Davis, CA 95616, USA; (T.C.); (P.V.)
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Sarno F, Nebbioso A, Altucci L. DOT1L: a key target in normal chromatin remodelling and in mixed-lineage leukaemia treatment. Epigenetics 2019; 15:439-453. [PMID: 31790636 PMCID: PMC7188393 DOI: 10.1080/15592294.2019.1699991] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Methylation of histone 3 at lysine 79 (H3K79) is one of the principal mechanisms involved in gene expression. The histone methyltransferase DOT1L, which mono-, di- and trimethylates H3K79 using S-adenosyl-L-methionine as a co-factor, is involved in cell development, cell cycle progression, and DNA damage repair. However, changes in normal expression levels of this enzyme are found in prostate, breast, and ovarian cancer. High levels of H3K79me are also detected in acute myeloid leukaemia patients bearing MLL rearrangements (MLL-r). MLL translocations are found in approximately 80% of paediatric patients, leading to poor prognosis. DOT1L is recruited on DNA and induces hyperexpression of HOXA9 and MEIS1. Based on these findings, selective drugs have been developed to induce apoptosis in MLL-r leukaemia cells by specifically inhibiting DOT1L. The most potent DOT1L inhibitor pinometostat has been investigated in Phase I clinical trials for treatment of paediatric and adult patients with MLL-driven leukaemia, showing promising results.
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Affiliation(s)
- Federica Sarno
- Dipartimento di Medicina di Precisione, Università degli Studi della Campania "Luigi Vanvitelli" Napoli, Napoli, Italy
| | - Angela Nebbioso
- Dipartimento di Medicina di Precisione, Università degli Studi della Campania "Luigi Vanvitelli" Napoli, Napoli, Italy
| | - Lucia Altucci
- Dipartimento di Medicina di Precisione, Università degli Studi della Campania "Luigi Vanvitelli" Napoli, Napoli, Italy
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Morcillo-Parra MÁ, Valera MJ, Beltran G, Mas A, Torija MJ. Glycolytic Proteins Interact With Intracellular Melatonin in Saccharomyces cerevisiae. Front Microbiol 2019; 10:2424. [PMID: 31708896 PMCID: PMC6821644 DOI: 10.3389/fmicb.2019.02424] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 10/08/2019] [Indexed: 02/03/2023] Open
Abstract
Melatonin is a bioactive compound that is present in fermented beverages and synthesized by yeast during alcoholic fermentation. Many studies have shown that melatonin interacts with some mammalian proteins, such as sirtuins or orphan receptor family proteins. The aim of this study was to determine the intracellular synthesis profile of melatonin in Saccharomyces cerevisiae and to identify the proteins that may interact with this molecule in yeast cells. Melatonin from fermentation samples was analyzed by liquid chromatography mass spectrometry, and proteins bound to melatonin were immunopurified by melatonin-IgG-Dynabeads. Melatonin was produced intracellularly in the lag phase of yeast growth and was exported to the extracellular media during the stationary phase. During this period, melatonin was bound to six proteins with molecular weights from 55 to 35 kDa. Sequence analysis showed that most proteins shared high levels of homology with glycolytic enzymes. An RNA-binding protein was also identified, the elongation alpha factor, which is related to mitochondria. This study reports for the first time the interaction of melatonin and proteins inside yeast cells. These results highlight the possible role of melatonin as a signal molecule and provide a new perspective for understanding its role in yeast.
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Affiliation(s)
| | - María José Valera
- Department de Bioquímica i Biotecnologia, Facultad d'Enologia, Universitat Rovira i Virgili, Tarragona, Spain
| | - Gemma Beltran
- Department de Bioquímica i Biotecnologia, Facultad d'Enologia, Universitat Rovira i Virgili, Tarragona, Spain
| | - Albert Mas
- Department de Bioquímica i Biotecnologia, Facultad d'Enologia, Universitat Rovira i Virgili, Tarragona, Spain
| | - María-Jesús Torija
- Department de Bioquímica i Biotecnologia, Facultad d'Enologia, Universitat Rovira i Virgili, Tarragona, Spain
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Kim DH, Jung IH, Kim DH, Park SW. Knockout of longevity gene Sirt1 in zebrafish leads to oxidative injury, chronic inflammation, and reduced life span. PLoS One 2019; 14:e0220581. [PMID: 31386694 PMCID: PMC6684063 DOI: 10.1371/journal.pone.0220581] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 07/18/2019] [Indexed: 11/19/2022] Open
Abstract
Sirt1, a member of the sirtuin gene family, encodes the most conserved mammalian NAD+-dependent deacetylase enzyme responsible for removing acetyl groups from many proteins. The Sirt1 gene is known as a longevity gene whose knockout in mice leads to decreased lifespan relative to the wild type. This study aimed to explore phenotypic changes in zebrafish Sirt1-knockouts and to investigate the function of the Sirt1 gene. Targeted knockout of Sirt1 in zebrafish (Danio rerio) was achieved using the CRISPR-Cas9 genome editing system. We created a 4-bp insertion-homozygote Sirt1-knockout zebrafish. Although there was no evident difference in appearance in the early stages of development, a significant increase in reactive oxygen species and in the extent of apoptosis in Sirt1-knockout zebrafish was observed. Sirt1 knockout caused inflammatory genes, including IL-1b, IL-6 and TNF-α to be highly expressed. Additionally, the lack of Sirt1 caused chronic inflammation and intestinal atrophy, thereby increasing pro-apoptotic events, which ultimately reduced the lifespan of transgenic zebrafish. Overall, our data demonstrate that lack of Sirt1 caused a significantly increased generation of reactive oxygen species that resulted in chronic inflammation and regeneration. Continuous repetition of these events played an important role in accelerating aging, thereby decreasing lifespan. Our findings using the knockout zebrafish model confirmed the association of the Sirt1 gene to aging processes and lifespan. Furthermore, the Sirt1-knockout mutant zebrafish developed in our study will surely be a valuable model to explore the mechanism of chronic inflammation.
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Affiliation(s)
- Do Hee Kim
- Postgraduate School of Nano Science and Technology, Yonsei University, Seoul, Korea
| | - In Hye Jung
- Department of Internal Medicine, Yonsei University College of Medicine, Institute of Gastroenterology, Severance Hospital, Seoul, Korea
| | - Dong Hee Kim
- Postgraduate School of Nano Science and Technology, Yonsei University, Seoul, Korea
| | - Seung Woo Park
- Department of Internal Medicine, Yonsei University College of Medicine, Institute of Gastroenterology, Severance Hospital, Seoul, Korea
- * E-mail:
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31
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The Capability of O-Acetyl-ADP-Ribose, an Epigenetic Metabolic Small Molecule, on Promoting the Further Spreading of Sir3 along the Telomeric Chromatin. Genes (Basel) 2019; 10:genes10080577. [PMID: 31366171 PMCID: PMC6723988 DOI: 10.3390/genes10080577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 07/23/2019] [Accepted: 07/27/2019] [Indexed: 11/17/2022] Open
Abstract
O-acetyl-ADP-ribose (AAR) is a metabolic small molecule relevant in epigenetics that is generated by NAD-dependent histone deacetylases, such as Sir2. The formation of silent heterochromatin in yeast requires histone deacetylation by Sir2, structural rearrangement of SIR complexes, spreading of SIR complexes along the chromatin, and additional maturation processing. AAR affects the interactions of the SIR-nucleosome in vitro and enhances the chromatin epigenetic silencing effect in vivo. In this study, using isothermal titration calorimetry (ITC) and dot blotting methods, we showed the direct interaction of AAR with Sir3. Furthermore, through chromatin immunoprecipitation (ChIP)-on-chip and chromatin affinity purification (ChAP)-on chip assays, we discovered that AAR is capable of increasing the extended spreading of Sir3 along telomeres, but not Sir2. In addition, the findings of a quantitative real-time polymerase chain reaction (qRT-PCR) and examinations of an in vitro assembly system of SIR-nucleosome heterochromatin filament were consistent with these results. This study provides evidence indicating another important effect of AAR in vivo. AAR may play a specific modulating role in the formation of silent SIR-nucleosome heterochromatin in yeast.
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Fine RD, Maqani N, Li M, Franck E, Smith JS. Depletion of Limiting rDNA Structural Complexes Triggers Chromosomal Instability and Replicative Aging of Saccharomyces cerevisiae. Genetics 2019; 212:75-91. [PMID: 30842210 PMCID: PMC6499517 DOI: 10.1534/genetics.119.302047] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Accepted: 03/01/2019] [Indexed: 12/12/2022] Open
Abstract
Sir2 is a highly conserved NAD+-dependent histone deacetylase that functions in heterochromatin formation and promotes replicative life span (RLS) in the budding yeast, Saccharomyces cerevisiae Within the yeast rDNA locus, Sir2 is required for efficient cohesin recruitment and maintaining the stability of the tandem array. In addition to the previously reported depletion of Sir2 in replicatively aged cells, we discovered that subunits of the Sir2-containing complexes silent information regulator (SIR) and regulator of nucleolar silencing and telophase (RENT) were depleted. Several other rDNA structural protein complexes also exhibited age-related depletion, most notably the cohesin complex. We hypothesized that mitotic chromosome instability (CIN) due to cohesin depletion could be a driver of replicative aging. Chromatin immunoprecipitation assays of the residual cohesin (Mcd1-Myc) in moderately aged cells showed strong depletion from the rDNA and initial redistribution to the point centromeres, which was then lost in older cells. Despite the shift in cohesin distribution, sister chromatid cohesion was partially attenuated in aged cells and the frequency of chromosome loss was increased. This age-induced CIN was exacerbated in strains lacking Sir2 and its paralog, Hst1, but suppressed in strains that stabilize the rDNA array due to deletion of FOB1 or through caloric restriction. Furthermore, ectopic expression of MCD1 from a doxycycline-inducible promoter was sufficient to suppress rDNA instability in aged cells and to extend RLS. Taken together, we conclude that age-induced depletion of cohesin and multiple other nucleolar chromatin factors destabilize the rDNA locus, which then results in general CIN and aneuploidy that shortens RLS.
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Affiliation(s)
- Ryan D Fine
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, Virginia 22908
| | - Nazif Maqani
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, Virginia 22908
| | - Mingguang Li
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, Virginia 22908
- Department of Laboratory Medicine, Jilin Medical University, 132013, China
| | - Elizabeth Franck
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, Virginia 22908
| | - Jeffrey S Smith
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, Virginia 22908
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Fob1p recruits DNA topoisomerase I to ribosomal genes locus and contributes to its transcriptional silencing maintenance. Int J Biochem Cell Biol 2019; 110:143-148. [PMID: 30880168 DOI: 10.1016/j.biocel.2019.03.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 03/08/2019] [Accepted: 03/12/2019] [Indexed: 11/20/2022]
Abstract
S. cerevisiae ribosomal DNA (rDNA) locus hosts a series of highly complex regulatory machineries for RNA polymerase I, II and III transcription, DNA replication and units recombination, all acting in the Non Transcribed Spacers (NTSs) interposed between the repeated units by which it is composed. DNA topoisomerase I (Top1p) contributes, recruiting Sir2p, to the maintenance of transcriptional silencing occurring at the RNA Polymerase II cryptic promoters, located in the NTS region. In this paper we found that Fob1p presence is crucial for Top1p recruitment at NTS, allowing transcriptional silencing to be established and maintained. We also showed the role of Nsr1p in Top1p recruitment to rDNA locus. Our work allows to hypothesize that Nsr1p targets Top1p into the nucleolus while Fob1p is responsible for its preferential distribution at RFB.
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Hannig K, Babl V, Hergert K, Maier A, Pilsl M, Schächner C, Stöckl U, Milkereit P, Tschochner H, Seufert W, Griesenbeck J. The C-terminal region of Net1 is an activator of RNA polymerase I transcription with conserved features from yeast to human. PLoS Genet 2019; 15:e1008006. [PMID: 30802237 PMCID: PMC6415870 DOI: 10.1371/journal.pgen.1008006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 03/13/2019] [Accepted: 02/05/2019] [Indexed: 01/25/2023] Open
Abstract
RNA polymerase I (Pol I) synthesizes ribosomal RNA (rRNA) in all eukaryotes, accounting for the major part of transcriptional activity in proliferating cells. Although basal Pol I transcription factors have been characterized in diverse organisms, the molecular basis of the robust rRNA production in vivo remains largely unknown. In S. cerevisiae, the multifunctional Net1 protein was reported to stimulate Pol I transcription. We found that the Pol I-stimulating function can be attributed to the very C-terminal region (CTR) of Net1. The CTR was required for normal cell growth and Pol I recruitment to rRNA genes in vivo and sufficient to promote Pol I transcription in vitro. Similarity with the acidic tail region of mammalian Pol I transcription factor UBF, which could partly functionally substitute for the CTR, suggests conserved roles for CTR-like domains in Pol I transcription from yeast to human. The production of ribosomes, cellular factories of protein synthesis, is an essential process driving proliferation and cell growth. Ribosome biogenesis is controlled at the level of synthesis of its components, ribosomal proteins and ribosomal RNA. In eukaryotes, RNA polymerase I is dedicated to transcribe the ribosomal RNA. RNA polymerase I has been identified as a potential target for cell proliferation inhibition. Here we describe the C-terminal region of Net1 as an activator of RNA polymerase I transcription in baker’s yeast. In the absence of this activator RNA polymerase I transcription is downregulated and cell proliferation is strongly impaired. Strikingly, this activator might be conserved in human cells, which points to a general mechanism. Our discovery will help to gain a better understanding of the molecular basis of ribosomal RNA synthesis and may have implications in developing strategies to control cellular growth.
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Affiliation(s)
- Katharina Hannig
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
| | - Virginia Babl
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
| | - Kristin Hergert
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
| | - Andreas Maier
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
| | - Michael Pilsl
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
| | - Christopher Schächner
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
| | - Ulrike Stöckl
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
| | - Philipp Milkereit
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
- * E-mail: (PM); (HT); (WS); (JG)
| | - Herbert Tschochner
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
- * E-mail: (PM); (HT); (WS); (JG)
| | - Wolfgang Seufert
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
- * E-mail: (PM); (HT); (WS); (JG)
| | - Joachim Griesenbeck
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
- * E-mail: (PM); (HT); (WS); (JG)
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Molano-Arevalo JC, Gonzalez W, Jeanne Dit Fouque K, Miksovska J, Maitre P, Fernandez-Lima F. Insights from ion mobility-mass spectrometry, infrared spectroscopy, and molecular dynamics simulations on nicotinamide adenine dinucleotide structural dynamics: NAD +vs. NADH. Phys Chem Chem Phys 2018; 20:7043-7052. [PMID: 29473073 DOI: 10.1039/c7cp05602h] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Nicotinamide adenine dinucleotide (NAD) is found in all living cells where the oxidized (NAD+) and reduced (NADH) forms play important roles in many enzymatic reactions. However, little is known about NAD+ and NADH conformational changes and kinetics as a function of the cell environment. In the present work, an analytical workflow is utilized to study NAD+ and NADH dynamics as a function of the organic content in solution using fluorescence lifetime spectroscopy and in the gas-phase using trapped ion mobility spectrometry coupled to mass spectrometry (TIMS-MS) and infrared multiple photon dissociation (IRMPD) spectroscopy. NAD solution time decay studies showed a two-component distribution, assigned to changes from a "close" to "open" conformation with the increase of the organic content. NAD gas-phase studies using nESI-TIMS-MS displayed two ion mobility bands for NAD+ protonated and sodiated species, while four and two ion mobility bands were observed for NADH protonated and sodiated species, respectively. Changes in the mobility profiles were observed for NADH as a function of the starting solution conditions and the time after desolvation, while NAD+ profiles showed no dependence. IRMPD spectroscopy of NAD+ and NADH protonated species in the 800-1800 and 3200-3700 cm-1 spectral regions showed common and signature bands between the NAD forms. Candidate structures were proposed for NAD+ and NADH kinetically trapped intermediates of the protonated and sodiated species, based on their collision cross sections and IR profiles. Results showed that NAD+ and NADH species exist in open, stack, and closed conformations and that the driving force for conformational dynamics is hydrogen bonding of the N-H-O and O-H-O forms with ribose rings.
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Conserved Pbp1/Ataxin-2 regulates retrotransposon activity and connects polyglutamine expansion-driven protein aggregation to lifespan-controlling rDNA repeats. Commun Biol 2018; 1:187. [PMID: 30417124 PMCID: PMC6218562 DOI: 10.1038/s42003-018-0187-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 10/09/2018] [Indexed: 12/17/2022] Open
Abstract
Ribosomal DNA (rDNA) repeat instability and protein aggregation are thought to be two major and independent drivers of cellular aging. Pbp1, the yeast ortholog of human ATXN2, maintains rDNA repeat stability and lifespan via suppression of RNA-DNA hybrids. ATXN2 polyglutamine expansion drives neurodegeneration causing spinocerebellar ataxia type 2 and promoting amyotrophic lateral sclerosis. Here, molecular characterization of Pbp1 revealed that its knockout or subjection to disease-modeling polyQ expansion represses Ty1 (Transposons of Yeast) retrotransposons by respectively promoting Trf4-depedendent RNA turnover and Ty1 Gag protein aggregation. This aggregation, but not its impact on retrotransposition, compromises rDNA repeat stability and shortens lifespan by hyper-activating Trf4-dependent turnover of intergenic ncRNA within the repeats. We uncover a function for the conserved Pbp1/ATXN2 proteins in the promotion of retrotransposition, create and describe powerful yeast genetic models of ATXN2-linked neurodegenerative diseases, and connect the major aging mechanisms of rDNA instability and protein aggregation.
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Chromatin Remodeling Factors Isw2 and Ino80 Regulate Chromatin, Replication, and Copy Number of the Saccharomyces cerevisiae Ribosomal DNA Locus. Genetics 2018; 210:1543-1556. [PMID: 30355728 DOI: 10.1534/genetics.118.301579] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 10/17/2018] [Indexed: 01/08/2023] Open
Abstract
In the budding yeast Saccharomyces cerevisiae, ribosomal RNA genes are encoded in a highly repetitive tandem array referred to as the ribosomal DNA (rDNA) locus. The yeast rDNA is the site of a diverse set of DNA-dependent processes, including transcription of ribosomal RNAs by RNA polymerases I and III, transcription of noncoding RNAs by RNA polymerase II, DNA replication initiation, replication fork blocking, and recombination-mediated regulation of rDNA repeat copy number. All of this takes place in the context of chromatin, but little is known about the roles played by ATP-dependent chromatin remodeling factors at the yeast rDNA. In this work, we report that the Isw2 and Ino80 chromatin remodeling factors are targeted to this highly repetitive locus. We characterize for the first time their function in modifying local chromatin structure, finding that loss of these factors decreases the fraction of actively transcribed 35S ribosomal RNA genes and the positioning of nucleosomes flanking the ribosomal origin of replication. In addition, we report that Isw2 and Ino80 promote efficient firing of the ribosomal origin of replication and facilitate the regulated increase of rDNA repeat copy number. This work significantly expands our understanding of the importance of ATP-dependent chromatin remodeling for rDNA biology.
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Evrin C, Maman JD, Diamante A, Pellegrini L, Labib K. Histone H2A-H2B binding by Pol α in the eukaryotic replisome contributes to the maintenance of repressive chromatin. EMBO J 2018; 37:embj.201899021. [PMID: 30104407 PMCID: PMC6166128 DOI: 10.15252/embj.201899021] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 06/18/2018] [Accepted: 07/24/2018] [Indexed: 11/13/2022] Open
Abstract
The eukaryotic replisome disassembles parental chromatin at DNA replication forks, but then plays a poorly understood role in the re‐deposition of the displaced histone complexes onto nascent DNA. Here, we show that yeast DNA polymerase α contains a histone‐binding motif that is conserved in human Pol α and is specific for histones H2A and H2B. Mutation of this motif in budding yeast cells does not affect DNA synthesis, but instead abrogates gene silencing at telomeres and mating‐type loci. Similar phenotypes are produced not only by mutations that displace Pol α from the replisome, but also by mutation of the previously identified histone‐binding motif in the CMG helicase subunit Mcm2, the human orthologue of which was shown to bind to histones H3 and H4. We show that chromatin‐derived histone complexes can be bound simultaneously by Mcm2, Pol α and the histone chaperone FACT that is also a replisome component. These findings indicate that replisome assembly unites multiple histone‐binding activities, which jointly process parental histones to help preserve silent chromatin during the process of chromosome duplication.
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Affiliation(s)
- Cecile Evrin
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, School of Life Sciences, University of Dundee, Dundee, UK
| | - Joseph D Maman
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Aurora Diamante
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Luca Pellegrini
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Karim Labib
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, School of Life Sciences, University of Dundee, Dundee, UK
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Khan RI, Nirzhor SSR, Akter R. A Review of the Recent Advances Made with SIRT6 and its Implications on Aging Related Processes, Major Human Diseases, and Possible Therapeutic Targets. Biomolecules 2018; 8:biom8030044. [PMID: 29966233 PMCID: PMC6164879 DOI: 10.3390/biom8030044] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2018] [Revised: 06/24/2018] [Accepted: 06/26/2018] [Indexed: 12/20/2022] Open
Abstract
Sirtuin 6 (SIRT6) is a nicotinamide adenine dinucleotide+ (NAD+) dependent enzyme and stress response protein that has sparked the curiosity of many researchers in different branches of the biomedical sciences. A unique member of the known Sirtuin family, SIRT6 has several different functions in multiple different molecular pathways related to DNA repair, glycolysis, gluconeogenesis, tumorigenesis, neurodegeneration, cardiac hypertrophic responses, and more. Only in recent times, however, did the potential usefulness of SIRT6 come to light as we learned more about its biochemical activity, regulation, biological roles, and structure Frye (2000). Even until very recently, SIRT6 was known more for chromatin signaling but, being a nascent topic of study, more information has been ascertained and its potential involvement in major human diseases including diabetes, cancer, neurodegenerative diseases, and heart disease. It is pivotal to explore the mechanistic workings of SIRT6 since future research may hold the key to engendering strategies involving SIRT6 that may have significant implications for human health and expand upon possible treatment options. In this review, we are primarily concerned with exploring the latest advances in understanding SIRT6 and how it can alter the course of several life-threatening diseases such as processes related to aging, cancer, neurodegenerative diseases, heart disease, and diabetes (SIRT6 has also shown to be involved in liver disease, inflammation, and bone-related issues) and any recent promising pharmacological investigations or potential therapeutics that are of interest.
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Affiliation(s)
| | | | - Raushanara Akter
- Department of Pharmacy, BRAC University, 1212 Dhaka, Bangladesh.
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Yi DG, Hong S, Huh WK. Mitochondrial dysfunction reduces yeast replicative lifespan by elevating RAS-dependent ROS production by the ER-localized NADPH oxidase Yno1. PLoS One 2018; 13:e0198619. [PMID: 29912878 PMCID: PMC6005541 DOI: 10.1371/journal.pone.0198619] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Accepted: 05/22/2018] [Indexed: 12/11/2022] Open
Abstract
Mitochondrial dysfunction leads to the accumulation of reactive oxygen species (ROS) which is associated with cellular dysfunction, disease etiology, and senescence. Here, we used the eukaryotic model Saccharomyces cerevisiae, commonly studied for cellular aging, to demonstrate how defective mitochondrial function affects yeast replicative lifespan (RLS). We show that RLS of respiratory-deficient cells decreases significantly, indicating that the maintenance of RLS requires active respiration. The shortening of RLS due to mitochondrial dysfunction was not related to the accumulation of extrachromosomal ribosomal DNA circles, a well-known cause of aging in yeast. Instead, intracellular ROS and oxidatively damaged proteins increased in respiratory-deficient mutants. We show that, while the protein kinase A activity is not elevated, ROS generation in respiratory-deficient cells depends on RAS signaling pathway. The ER-localized NADPH oxidase Yno1 also played a role in producing ROS. Our data suggest that a severe defect in mitochondrial respiration accelerates cellular aging by disturbing protein homeostasis in yeast.
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Affiliation(s)
- Dae-Gwan Yi
- Department of Biological Sciences, Seoul National University, Seoul, Republic of Korea
| | - Sujin Hong
- Department of Biological Sciences, Seoul National University, Seoul, Republic of Korea
| | - Won-Ki Huh
- Department of Biological Sciences, Seoul National University, Seoul, Republic of Korea
- Institute of Microbiology, Seoul National University, Seoul, Republic of Korea
- * E-mail:
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Hoggard TA, Chang F, Perry KR, Subramanian S, Kenworthy J, Chueng J, Shor E, Hyland EM, Boeke JD, Weinreich M, Fox CA. Yeast heterochromatin regulators Sir2 and Sir3 act directly at euchromatic DNA replication origins. PLoS Genet 2018; 14:e1007418. [PMID: 29795547 PMCID: PMC5991416 DOI: 10.1371/journal.pgen.1007418] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 06/06/2018] [Accepted: 05/15/2018] [Indexed: 01/23/2023] Open
Abstract
Most active DNA replication origins are found within euchromatin, while origins within heterochromatin are often inactive or inhibited. In yeast, origin activity within heterochromatin is negatively controlled by the histone H4K16 deacetylase, Sir2, and at some heterochromatic loci also by the nucleosome binding protein, Sir3. The prevailing view has been that direct functions of Sir2 and Sir3 are confined to heterochromatin. However, growth defects in yeast mutants compromised for loading the MCM helicase, such as cdc6-4, are suppressed by deletion of either SIR2 or SIR3. While these and other observations indicate that SIR2,3 can have a negative impact on at least some euchromatic origins, the genomic scale of this effect was unknown. It was also unknown whether this suppression resulted from direct functions of Sir2,3 within euchromatin, or was an indirect effect of their previously established roles within heterochromatin. Using MCM ChIP-Seq, we show that a SIR2 deletion rescued MCM complex loading at ~80% of euchromatic origins in cdc6-4 cells. Therefore, Sir2 exhibited a pervasive effect at the majority of euchromatic origins. Using MNase-H4K16ac ChIP-Seq, we show that origin-adjacent nucleosomes were depleted for H4K16 acetylation in a SIR2-dependent manner in wild type (i.e. CDC6) cells. In addition, we present evidence that both Sir2 and Sir3 bound to nucleosomes adjacent to euchromatic origins. The relative levels of each of these molecular hallmarks of yeast heterochromatin–SIR2-dependent H4K16 hypoacetylation, Sir2, and Sir3 –correlated with how strongly a SIR2 deletion suppressed the MCM loading defect in cdc6-4 cells. Finally, a screen for histone H3 and H4 mutants that could suppress the cdc6-4 growth defect identified amino acids that map to a surface of the nucleosome important for Sir3 binding. We conclude that heterochromatin proteins directly modify the local chromatin environment of euchromatic DNA replication origins. When a cell divides, it must copy or “replicate” its DNA. DNA replication starts at chromosomal regions called origins when a collection of replication proteins gains local access to unwind the two DNA strands. Chromosomal DNA is packaged into a protein-DNA complex called chromatin and there are two major structurally and functionally distinct types. Euchromatin allows DNA replication proteins to access origin DNA, while heterochromatin inhibits their access. The prevalent view has been that the heterochromatin proteins required to inhibit origins are confined to heterochromatin. In this study, the conserved heterochromatin proteins, Sir2 and Sir3, were shown to both physically and functionally associate with the majority of origins in euchromatin. This observation raises important questions about the chromosomal targets of heterochromatin proteins, and how and why the majority of origins exist within a potentially repressive chromatin structure.
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Affiliation(s)
- Timothy A. Hoggard
- Department of Biomolecular Chemistry, School of Medicine and Public Health, Madison, WI, United States of America
| | - FuJung Chang
- Laboratory of Genome Integrity and Tumorigenesis, Van Andel Research Institute, Grand Rapids, MI, United States of America
| | - Kelsey Rae Perry
- Department of Biomolecular Chemistry, School of Medicine and Public Health, Madison, WI, United States of America
- Integrated Program in Biochemistry, School of Medicine and Public Health and College of Agricultural Sciences, University of Wisconsin, Madison, WI, United States of America
| | - Sandya Subramanian
- Laboratory of Genome Integrity and Tumorigenesis, Van Andel Research Institute, Grand Rapids, MI, United States of America
| | - Jessica Kenworthy
- Laboratory of Genome Integrity and Tumorigenesis, Van Andel Research Institute, Grand Rapids, MI, United States of America
| | - Julie Chueng
- Integrated Program in Biochemistry, School of Medicine and Public Health and College of Agricultural Sciences, University of Wisconsin, Madison, WI, United States of America
| | - Erika Shor
- Public Health Research Institute, New Jersey Medical School, Rutgers University, Newark, New Jersey, United States of America
| | - Edel M. Hyland
- School of Biological Sciences, Medical Biology Center, Queen’s University, Belfast, United Kingdom
| | - Jef D. Boeke
- Department of Biochemistry and Molecular Pharmacology, Institute for Systems Genetics and NYU Langone Health, New York, NY, United States of America
| | - Michael Weinreich
- Laboratory of Genome Integrity and Tumorigenesis, Van Andel Research Institute, Grand Rapids, MI, United States of America
- * E-mail: (MW); (CAF)
| | - Catherine A. Fox
- Department of Biomolecular Chemistry, School of Medicine and Public Health, Madison, WI, United States of America
- Integrated Program in Biochemistry, School of Medicine and Public Health and College of Agricultural Sciences, University of Wisconsin, Madison, WI, United States of America
- * E-mail: (MW); (CAF)
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Tiku V, Antebi A. Nucleolar Function in Lifespan Regulation. Trends Cell Biol 2018; 28:662-672. [PMID: 29779866 DOI: 10.1016/j.tcb.2018.03.007] [Citation(s) in RCA: 98] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 03/26/2018] [Accepted: 03/29/2018] [Indexed: 12/12/2022]
Abstract
The nucleolus is a prominent membraneless organelle residing within the nucleus. The nucleolus has been regarded as a housekeeping structure mainly known for its role in ribosomal RNA (rRNA) production and ribosome assembly. However, accumulating evidence has revealed its functions in numerous cellular processes that control organismal physiology, thereby taking the nucleolus much beyond its conventional role in ribosome biogenesis. Perturbations in nucleolar functions have been associated with severe diseases such as cancer and progeria. Recent studies have also uncovered the role of the nucleolus in development and aging. In this review we discuss major nucleolar functions that impact organismal aging.
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Affiliation(s)
- Varnesh Tiku
- Max Planck Institute for Biology of Ageing, Joseph Stelzmann Strasse 9b, 50931 Cologne, Germany; Present Address: Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Adam Antebi
- Max Planck Institute for Biology of Ageing, Joseph Stelzmann Strasse 9b, 50931 Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50674 Cologne, Germany.
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43
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Paredes S, Angulo-Ibanez M, Tasselli L, Carlson SM, Zheng W, Li TM, Chua KF. The epigenetic regulator SIRT7 guards against mammalian cellular senescence induced by ribosomal DNA instability. J Biol Chem 2018; 293:11242-11250. [PMID: 29728458 DOI: 10.1074/jbc.ac118.003325] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 04/21/2018] [Indexed: 12/16/2022] Open
Abstract
In the yeast Saccharomyces cerevisiae, genomic instability in rDNA repeat sequences is an underlying cause of cell aging and is suppressed by the chromatin-silencing factor Sir2. In humans, rDNA instability is observed in cancers and premature aging syndromes, but its underlying mechanisms and functional consequences remain unclear. Here, we uncovered a pivotal role of sirtuin 7 (SIRT7), a mammalian Sir2 homolog, in guarding against rDNA instability and show that this function of SIRT7 protects against senescence in primary human cells. We found that, mechanistically, SIRT7 is required for association of SNF2H (also called SMARCA5, SWI/SNF-related matrix-associated actin-dependent regulator of chromatin, subfamily A, member 5), a component of the nucleolar heterochromatin-silencing complex NoRC, with rDNA sequences. Defective rDNA-heterochromatin silencing in SIRT7-deficient cells unleashed rDNA instability, with excision and loss of rDNA gene copies, which in turn induced acute senescence. Mounting evidence indicates that accumulation of senescent cells significantly contributes to tissue dysfunction in aging-related pathologies. Our findings identify rDNA instability as a driver of mammalian cellular senescence and implicate SIRT7-dependent heterochromatin silencing in protecting against this process.
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Affiliation(s)
- Silvana Paredes
- From the Department of Medicine, Stanford University School of Medicine, Stanford, California 94305.,Geriatric Research, Education, and Clinical Center, Veterans Affairs Palo Alto Health Care System, Palo Alto, California 94304, and
| | - Maria Angulo-Ibanez
- From the Department of Medicine, Stanford University School of Medicine, Stanford, California 94305.,Geriatric Research, Education, and Clinical Center, Veterans Affairs Palo Alto Health Care System, Palo Alto, California 94304, and
| | - Luisa Tasselli
- From the Department of Medicine, Stanford University School of Medicine, Stanford, California 94305.,Geriatric Research, Education, and Clinical Center, Veterans Affairs Palo Alto Health Care System, Palo Alto, California 94304, and
| | - Scott M Carlson
- Department of Biology, Stanford University, Stanford, California 94305
| | - Wei Zheng
- From the Department of Medicine, Stanford University School of Medicine, Stanford, California 94305.,Geriatric Research, Education, and Clinical Center, Veterans Affairs Palo Alto Health Care System, Palo Alto, California 94304, and
| | - Tie-Mei Li
- From the Department of Medicine, Stanford University School of Medicine, Stanford, California 94305.,Geriatric Research, Education, and Clinical Center, Veterans Affairs Palo Alto Health Care System, Palo Alto, California 94304, and
| | - Katrin F Chua
- From the Department of Medicine, Stanford University School of Medicine, Stanford, California 94305, .,Geriatric Research, Education, and Clinical Center, Veterans Affairs Palo Alto Health Care System, Palo Alto, California 94304, and
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44
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Zainabadi K. A brief history of modern aging research. Exp Gerontol 2018; 104:35-42. [DOI: 10.1016/j.exger.2018.01.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 01/15/2018] [Indexed: 11/16/2022]
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45
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Abstract
As the popular adage goes, all diseases run into old age and almost all physiological changes are associated with alterations in gene expression, irrespective of whether they are causal or consequential. Therefore, the quest for mechanisms that delay ageing and decrease age-associated diseases has propelled researchers to unravel regulatory factors that lead to changes in chromatin structure and function, which ultimately results in deregulated gene expression. It is therefore essential to bring together literature, which until recently has investigated gene expression and chromatin independently. With advances in biomedical research and the emergence of epigenetic regulators as potential therapeutic targets, enhancing our understanding of mechanisms that 'derail' transcription and identification of causal genes/pathways during ageing will have a significant impact. In this context, this chapter aims to not only summarize the key features of age-associated changes in epigenetics and transcription, but also identifies gaps in the field and proposes aspects that need to be investigated in the future.
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46
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Yu J, Qin B, Wu F, Qin S, Nowsheen S, Shan S, Zayas J, Pei H, Lou Z, Wang L. Regulation of Serine-Threonine Kinase Akt Activation by NAD +-Dependent Deacetylase SIRT7. Cell Rep 2017; 18:1229-1240. [PMID: 28147277 DOI: 10.1016/j.celrep.2017.01.009] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 12/02/2016] [Accepted: 01/06/2017] [Indexed: 12/15/2022] Open
Abstract
The Akt pathway is a central regulator that promotes cell survival in response to extracellular signals. Depletion of SIRT7, an NAD+-dependent deacetylase that is the least-studied sirtuin, is known to significantly increase Akt activity in mice through unknown mechanisms. In this study, we demonstrate that SIRT7 depletion in breast cancer cells results in Akt hyper-phosphorylation and increases cell survival following genotoxic stress. Mechanistically, SIRT7 specifically interacts with and deacetylates FKBP51 at residue lysines 28 and 155 (K28 and K155), resulting in enhanced interactions among FKBP51, Akt, and PHLPP, as well as Akt dephosphorylation. Mutating both lysines to arginines abolishes the effect of SIRT7 on Akt activity through FKBP51 deacetylation. Finally, energy stress strengthens SIRT7-mediated effects on Akt dephosphorylation through FKBP51 and thus sensitizes cancer cells to cytotoxic agents. These results reveal a direct role of SIRT7 in Akt regulation and raise the possibility of using the glucose analog 2-deoxy-D-glucose (2DG) as a chemo-sensitizing agent.
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Affiliation(s)
- Jia Yu
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA
| | - Bo Qin
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA; Division of Medical Oncology, Mayo Clinic, Rochester, MN 55905, USA
| | - Fengying Wu
- Department of Oncology, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai 200433, China
| | - Sisi Qin
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA
| | - Somaira Nowsheen
- Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic School of Medicine and the Mayo Clinic Medical Scientist Training Program, Rochester, MN 55905, USA
| | - Shan Shan
- Department of Respiratory Medicine, East Hospital, Tongji University School of Medicine, Shanghai 200120, China
| | - Jacqueline Zayas
- Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic School of Medicine and the Mayo Clinic Medical Scientist Training Program, Rochester, MN 55905, USA
| | - Huadong Pei
- Division of Medical Oncology, Mayo Clinic, Rochester, MN 55905, USA; Beijing Proteome Research Center, Beijing Institute of Radiation Medicine, Beijing 100850, China
| | - Zhenkun Lou
- Division of Medical Oncology, Mayo Clinic, Rochester, MN 55905, USA.
| | - Liewei Wang
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA.
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47
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Ho L, Wang L, Roth TM, Pan Y, Verdin EM, Hsiao EC, Nissenson RA. Sirtuin-3 Promotes Adipogenesis, Osteoclastogenesis, and Bone Loss in Aging Male Mice. Endocrinology 2017; 158:2741-2753. [PMID: 28911171 PMCID: PMC5659662 DOI: 10.1210/en.2016-1739] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 07/05/2017] [Indexed: 12/22/2022]
Abstract
Sirtuin-3 (Sirt3) is an essential metabolic regulatory enzyme that plays an important role in mitochondrial metabolism, but its role in bone marrow and skeletal homeostasis remains largely unknown. In this study, we hypothesize that increased expression of Sirt3 plays a role in skeletal aging. Using mice that overexpress Sirt3 [i.e., Sirt3 transgenic (Sirt3Tg)], we show that Sirt3 is a positive regulator of adipogenesis and osteoclastogenesis and a negative regulator of skeletal homeostasis. Sirt3Tg mice exhibited more adipocytes in the tibia compared with control mice. Bone marrow stromal cells (BMSCs) from Sirt3Tg mice displayed an enhanced ability to differentiate into adipocytes compared with control BMSCs. We found a 2.5-fold increase in the number of osteoclasts on the bone surface in Sirt3Tg mice compared with control mice (P < 0.03), and increased osteoclastogenesis in vitro. Importantly, Sirt3 activates the mechanistic target of rapamycin (mTOR) pathway to regulate osteoclastogenesis. Sirt3Tg male mice exhibited a significant reduction in cortical thickness at the tibiofibular junction (P < 0.05). In summary, Sirt3 activity in bone marrow cells is associated with increased adipogenesis, increased osteoclastogenesis through activation of mTOR signaling, and reduced bone mass. Interestingly, Sirt3 expression in bone marrow cells increases during aging, suggesting that Sirt3 promotes age-related adipogenesis and osteoclastogenesis associated with bone loss. These findings identify Sirt3 as an important regulator of adipogenesis and skeletal homeostasis in vivo and identify Sirt3 as a potential target for the treatment of osteoporosis.
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Affiliation(s)
- Linh Ho
- Endocrine Research Unit, VA Medical Center and Departments of Medicine and Physiology, University of California, San Francisco, San Francisco, California 94158
| | - Liping Wang
- Endocrine Research Unit, VA Medical Center and Departments of Medicine and Physiology, University of California, San Francisco, San Francisco, California 94158
| | - Theresa M. Roth
- Endocrine Research Unit, VA Medical Center and Departments of Medicine and Physiology, University of California, San Francisco, San Francisco, California 94158
| | - Yong Pan
- Gladstone Institutes, University of California, San Francisco, San Francisco, California 94941
| | - Eric M. Verdin
- Gladstone Institutes, University of California, San Francisco, San Francisco, California 94941
| | - Edward C. Hsiao
- Division of Endocrinology and Metabolism, Institute for Human Genetics, University of California, San Francisco, San Francisco, California 94143
| | - Robert A. Nissenson
- Endocrine Research Unit, VA Medical Center and Departments of Medicine and Physiology, University of California, San Francisco, San Francisco, California 94158
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48
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Puddu F, Salguero I, Herzog M, Geisler NJ, Costanzo V, Jackson SP. Chromatin determinants impart camptothecin sensitivity. EMBO Rep 2017; 18:1000-1012. [PMID: 28389464 PMCID: PMC5452016 DOI: 10.15252/embr.201643560] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 03/07/2017] [Accepted: 03/09/2017] [Indexed: 11/09/2022] Open
Abstract
Camptothecin-induced locking of topoisomerase 1 on DNA generates a physical barrier to replication fork progression and creates topological stress. By allowing replisome rotation, absence of the Tof1/Csm3 complex promotes the conversion of impending topological stress to DNA catenation and causes camptothecin hypersensitivity. Through synthetic viability screening, we discovered that histone H4 K16 deacetylation drives the sensitivity of yeast cells to camptothecin and that inactivation of this pathway by mutating H4 K16 or the genes SIR1-4 suppresses much of the hypersensitivity of tof1∆ strains towards this agent. We show that disruption of rDNA or telomeric silencing does not mediate camptothecin resistance but that disruption of Sir1-dependent chromatin domains is sufficient to suppress camptothecin sensitivity in wild-type and tof1∆ cells. We suggest that topoisomerase 1 inhibition in proximity of these domains causes topological stress that leads to DNA hypercatenation, especially in the absence of the Tof1/Csm3 complex. Finally, we provide evidence of the evolutionarily conservation of this mechanism.
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Affiliation(s)
- Fabio Puddu
- The Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Israel Salguero
- The Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Mareike Herzog
- The Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, UK
- The Wellcome Trust Sanger Institute, Hinxton Cambridge, UK
| | - Nicola J Geisler
- The Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Vincenzo Costanzo
- IFOM (Fondazione Istituto FIRC di Oncologia Molecolare), Milan, Italy
| | - Stephen P Jackson
- The Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, UK
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49
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The Nuts and Bolts of Transcriptionally Silent Chromatin in Saccharomyces cerevisiae. Genetics 2017; 203:1563-99. [PMID: 27516616 DOI: 10.1534/genetics.112.145243] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 05/30/2016] [Indexed: 12/31/2022] Open
Abstract
Transcriptional silencing in Saccharomyces cerevisiae occurs at several genomic sites including the silent mating-type loci, telomeres, and the ribosomal DNA (rDNA) tandem array. Epigenetic silencing at each of these domains is characterized by the absence of nearly all histone modifications, including most prominently the lack of histone H4 lysine 16 acetylation. In all cases, silencing requires Sir2, a highly-conserved NAD(+)-dependent histone deacetylase. At locations other than the rDNA, silencing also requires additional Sir proteins, Sir1, Sir3, and Sir4 that together form a repressive heterochromatin-like structure termed silent chromatin. The mechanisms of silent chromatin establishment, maintenance, and inheritance have been investigated extensively over the last 25 years, and these studies have revealed numerous paradigms for transcriptional repression, chromatin organization, and epigenetic gene regulation. Studies of Sir2-dependent silencing at the rDNA have also contributed to understanding the mechanisms for maintaining the stability of repetitive DNA and regulating replicative cell aging. The goal of this comprehensive review is to distill a wide array of biochemical, molecular genetic, cell biological, and genomics studies down to the "nuts and bolts" of silent chromatin and the processes that yield transcriptional silencing.
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50
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Hirvonen K, Laivuori H, Lahti J, Strandberg T, Eriksson JG, Hackman P. SIRT6 polymorphism rs117385980 is associated with longevity and healthy aging in Finnish men. BMC MEDICAL GENETICS 2017; 18:41. [PMID: 28399814 PMCID: PMC5387321 DOI: 10.1186/s12881-017-0401-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 03/30/2017] [Indexed: 01/13/2023]
Abstract
Background Sirtuin-6 (SIRT6) is involved in various crucial cellular pathways, being a key regulator of telomere structure, DNA repair, metabolism, transcriptional control and the NF-kappa B pathway. Sirt6 knock-out mice have been reported to develop typical features of aging and senescence at the age of 2–3 weeks and die within 4 weeks. The aim of this study was to investigate whether sequence variations of SIRT6 are associated with aging and longevity in Finnish men. Methods The sample of this study consisted of 43 longer-living and healthy males and 92 male control subjects who have died of natural causes at an average age of 66,6 (±4,1) years and who belonged to the Helsinki Birth Cohort Study (HBCS). Single nucleotide polymorphisms (SNPs) in the exons and their surroundings of the SIRT6 were studied using direct PCR sequencing. Results The SNP rs117385980 (C > T), situated 23 bases downstream of the exon 2 exon/intron border was found in heterozygous form in 1/43 longer-living healthy men (Minor allele frequency (MAF) 0,0116) and in 9/92 controls (MAF 0,0489). To replicate this finding, we studied a group of 63 healthy men at an average age of 83 years from the Helsinki Businessmen Study (HBS)–cohort. The heterozygosity of the same SNP was seen in 2/63 men from the HBS–cohort (MAF 0,0159). Fisher exact test was performed in our two combined study samples. The P-value for all samples combined was 0.07 and the odds ratio 3.53 (95% confidence interval 0.96–13.4). Conclusions These results suggest an inverse association between the T allele of rs117385980 and longevity. The result needs to be confirmed in a larger study. It remains to be determined whether rs117385980 itself has an effect or if it is a mere genetic marker for some other yet undiscovered sequence variant causing a functional effect.
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Affiliation(s)
- Katariina Hirvonen
- The Folkhälsan Institute of Genetics and the Department of Medical Genetics, University of Helsinki, Helsinki, Finland.
| | - Hannele Laivuori
- Medical and Clinical Genetics and Obstetrics and Gynecology, University of Helsinki, Helsinki, Finland.,Helsinki University Hospital, Helsinki, Finland.,Institute for Molecular Medicine Finland, University of Helsinki, Helsinki, Finland
| | - Jari Lahti
- Institute of Behavioural Sciences, University of Helsinki, Helsinki, Finland.,Folkhälsan Research Centre, Helsinki, Finland
| | - Timo Strandberg
- University of Helsinki, Helsinki, Finland.,Helsinki University Central Hospital, Geriatrics, Helsinki, Finland.,Institute of Health Sciences/Geriatrics, University of Oulu, Oulu, Finland
| | - Johan G Eriksson
- Folkhälsan Research Centre, Helsinki, Finland.,University of Helsinki, Helsinki, Finland.,Department Chronic Disease Prevention, National Institute for Health and Welfare, Helsinki, Finland.,Department of General Practice and Primary Health Care, Helsinki University Hospital, Helsinki, Finland
| | - Peter Hackman
- The Folkhälsan Institute of Genetics and the Department of Medical Genetics, University of Helsinki, Helsinki, Finland
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