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Akematsu T, Loidl J, Fukuda Y, Iwamoto M. Close cooperation between Semi1 and Semi2 proteins is essential for pronuclear positioning in Tetrahymena thermophila. Mol Biol Cell 2025; 36:ar23. [PMID: 39785685 PMCID: PMC11974950 DOI: 10.1091/mbc.e24-11-0503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2024] [Revised: 01/02/2025] [Accepted: 01/03/2025] [Indexed: 01/12/2025] Open
Abstract
During sexual reproduction in the ciliate Tetrahymena thermophila, meiosis occurs in the germline micronucleus, resulting in the formation of four haploid micronuclei. Of these, only one is selected to evade autophagy, and subsequently migrates to the membrane junction with the partner cell for reciprocal pronuclear exchange. We previously demonstrated that the transmembrane protein Semi1 is essential for this nuclear migration. Semi1 is specifically expressed in mating cells and localizes to the periphery of the selected nucleus. Loss of Semi1 disrupts nuclear attachment to the junction, leading to infertility. However, the mechanism by which Semi1 positions the nucleus at the junction remains unclear. Here, we report that the Semi1-interacting protein, Semi2, is also necessary for proper nuclear positioning. Deletion of Semi2 results in the same nuclear mislocalization phenotype and infertility observed in Semi1 mutant cells. Semi2 colocalizes with Semi1, but in the absence of Semi1, Semi2 fails to exhibit perinuclear localization. The selected nucleus anchors to microtubules prior to migration, a process dependent on both Semi1 and Semi2. We propose a model in which Semi1 recruits Semi2 to the selected nucleus, facilitating the interaction between the nucleus and microtubules required for proper nuclear positioning at the membrane junction.
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Affiliation(s)
- Takahiko Akematsu
- Department of Biosciences, College of Humanities and Sciences, Nihon University, Tokyo 156-8550, Japan
- Department of Biology, Faculty of Science, Kanagawa University, Yokohama 221-8686, Japan
| | - Josef Loidl
- Department of Chromosome Biology, University of Vienna, Vienna 1030, Austria
| | - Yasuhiro Fukuda
- Department of Biodiversity Science, Division of Biological Resource Science, Graduate School of Agricultural Science, Tohoku University, Oosaki 989-6711, Japan
| | - Masaaki Iwamoto
- Department of Biosciences, College of Humanities and Sciences, Nihon University, Tokyo 156-8550, Japan
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2
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Kitaoka M, Yamashita YM. Running the gauntlet: challenges to genome integrity in spermiogenesis. Nucleus 2024; 15:2339220. [PMID: 38594652 PMCID: PMC11005813 DOI: 10.1080/19491034.2024.2339220] [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: 02/23/2024] [Accepted: 04/02/2024] [Indexed: 04/11/2024] Open
Abstract
Species' continuity depends on gametogenesis to produce the only cell types that can transmit genetic information across generations. Spermiogenesis, which encompasses post-meiotic, haploid stages of male gametogenesis, is a process that leads to the formation of sperm cells well-known for their motility. Spermiogenesis faces three major challenges. First, after two rounds of meiotic divisions, the genome lacks repair templates (no sister chromatids, no homologous chromosomes), making it incredibly vulnerable to any genomic insults over an extended time (typically days-weeks). Second, the sperm genome becomes transcriptionally silent, making it difficult to respond to new perturbations as spermiogenesis progresses. Third, the histone-to-protamine transition, which is essential to package the sperm genome, counterintuitively involves DNA break formation. How spermiogenesis handles these challenges remains poorly understood. In this review, we discuss each challenge and their intersection with the biology of protamines. Finally, we discuss the implication of protamines in the process of evolution.
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Affiliation(s)
- Maiko Kitaoka
- Whitehead Institute for Biomedical Research and Howard Hughes Medical Institute, Cambridge, MA, USA
| | - Yukiko M. Yamashita
- Whitehead Institute for Biomedical Research and Howard Hughes Medical Institute, Cambridge, MA, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
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3
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Wojtaszek JL, Williams RS. From the TOP: Formation, recognition and resolution of topoisomerase DNA protein crosslinks. DNA Repair (Amst) 2024; 142:103751. [PMID: 39180935 PMCID: PMC11404304 DOI: 10.1016/j.dnarep.2024.103751] [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: 04/22/2024] [Revised: 08/07/2024] [Accepted: 08/12/2024] [Indexed: 08/27/2024]
Abstract
Since the report of "DNA untwisting" activity in 1972, ∼50 years of research has revealed seven topoisomerases in humans (TOP1, TOP1mt, TOP2α, TOP2β, TOP3α, TOP3β and Spo11). These conserved regulators of DNA topology catalyze controlled breakage to the DNA backbone to relieve the torsional stress that accumulates during essential DNA transactions including DNA replication, transcription, and DNA repair. Each topoisomerase-catalyzed reaction involves the formation of a topoisomerase cleavage complex (TOPcc), a covalent protein-DNA reaction intermediate formed between the DNA phosphodiester backbone and a topoisomerase catalytic tyrosine residue. A variety of perturbations to topoisomerase reaction cycles can trigger failure of the enzyme to re-ligate the broken DNA strand(s), thereby generating topoisomerase DNA-protein crosslinks (TOP-DPC). TOP-DPCs pose unique threats to genomic integrity. These complex lesions are comprised of structurally diverse protein components covalently linked to genomic DNA, which are bulky DNA adducts that can directly impact progression of the transcription and DNA replication apparatus. A variety of genome maintenance pathways have evolved to recognize and resolve TOP-DPCs. Eukaryotic cells harbor tyrosyl DNA phosphodiesterases (TDPs) that directly reverse 3'-phosphotyrosyl (TDP1) and 5'-phoshotyrosyl (TDP2) protein-DNA linkages. The broad specificity Mre11-Rad50-Nbs1 and APE2 nucleases are also critical for mitigating topoisomerase-generated DNA damage. These DNA-protein crosslink metabolizing enzymes are further enabled by proteolytic degradation, with the proteasome, Spartan, GCNA, Ddi2, and FAM111A proteases implicated thus far. Strategies to target, unfold, and degrade the protein component of TOP-DPCs have evolved as well. Here we survey mechanisms for addressing Topoisomerase 1 (TOP1) and Topoisomerase 2 (TOP2) DPCs, highlighting systems for which molecular structure information has illuminated function of these critical DNA damage response pathways.
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Affiliation(s)
- Jessica L Wojtaszek
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, US National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709, United States
| | - R Scott Williams
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, US National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709, United States.
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Jovanska L, Lin IC, Yao JS, Chen CL, Liu HC, Li WC, Chuang YC, Chuang CN, Yu ACH, Lin HN, Pong WL, Yu CI, Su CY, Chen YP, Chen RS, Hsueh YP, Yuan HS, Timofejeva L, Wang TF. DNA cytosine methyltransferases differentially regulate genome-wide hypermutation and interhomolog recombination in Trichoderma reesei meiosis. Nucleic Acids Res 2024; 52:9551-9573. [PMID: 39021337 PMCID: PMC11381340 DOI: 10.1093/nar/gkae611] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 06/20/2024] [Accepted: 07/01/2024] [Indexed: 07/20/2024] Open
Abstract
Trichoderma reesei is an economically important enzyme producer with several unique meiotic features. spo11, the initiator of meiotic double-strand breaks (DSBs) in most sexual eukaryotes, is dispensable for T. reesei meiosis. T. reesei lacks the meiosis-specific recombinase Dmc1. Rad51 and Sae2, the activator of the Mre11 endonuclease complex, promote DSB repair and chromosome synapsis in wild-type and spo11Δ meiosis. DNA methyltransferases (DNMTs) perform multiple tasks in meiosis. Three DNMT genes (rid1, dim2 and dimX) differentially regulate genome-wide cytosine methylation and C:G-to-T:A hypermutations in different chromosomal regions. We have identified two types of DSBs: type I DSBs require spo11 or rid1 for initiation, whereas type II DSBs do not rely on spo11 and rid1 for initiation. rid1 (but not dim2) is essential for Rad51-mediated DSB repair and normal meiosis. rid1 and rad51 exhibit a locus heterogeneity (LH) relationship, in which LH-associated proteins often regulate interconnectivity in protein interaction networks. This LH relationship can be suppressed by deleting dim2 in a haploid rid1Δ (but not rad51Δ) parental strain, indicating that dim2 and rid1 share a redundant function that acts earlier than rad51 during early meiosis. In conclusion, our studies provide the first evidence of the involvement of DNMTs during meiotic initiation and recombination.
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Affiliation(s)
| | - I-Chen Lin
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
- Chi-Mei Medical Center, Tainan 71004, Taiwan
| | - Jhong-Syuan Yao
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Chia-Ling Chen
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Hou-Cheng Liu
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Wan-Chen Li
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Yu-Chien Chuang
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Chi-Ning Chuang
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | | | - Hsin-Nan Lin
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Wen-Li Pong
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Chang-I Yu
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Ching-Yuan Su
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Yi-Ping Chen
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Ruey-Shyang Chen
- Department of Biochemical Science and Technology, National Chiayi University, Chiayi, Taiwan
| | - Yi-Ping Hsueh
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Hanna S Yuan
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Ljudmilla Timofejeva
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
- Centre of Estonian Rural Research and Knowledge, J. Aamisepa 1, Jõgeva 48309, Estonia
| | - Ting-Fang Wang
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
- Department of Biochemical Science and Technology, National Chiayi University, Chiayi, Taiwan
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Brand CL, Oliver GT, Farkas IZ, Buszczak M, Levine MT. Recurrent Duplication and Diversification of a Vital DNA Repair Gene Family Across Drosophila. Mol Biol Evol 2024; 41:msae113. [PMID: 38865490 PMCID: PMC11210505 DOI: 10.1093/molbev/msae113] [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: 11/07/2023] [Revised: 05/30/2024] [Accepted: 06/04/2024] [Indexed: 06/14/2024] Open
Abstract
Maintaining genome integrity is vital for organismal survival and reproduction. Essential, broadly conserved DNA repair pathways actively preserve genome integrity. However, many DNA repair proteins evolve adaptively. Ecological forces like UV exposure are classically cited drivers of DNA repair evolution. Intrinsic forces like repetitive DNA, which also imperil genome integrity, have received less attention. We recently reported that a Drosophila melanogaster-specific DNA satellite array triggered species-specific, adaptive evolution of a DNA repair protein called Spartan/MH. The Spartan family of proteases cleave hazardous, covalent crosslinks that form between DNA and proteins ("DNA-protein crosslink repair"). Appreciating that DNA satellites are both ubiquitous and universally fast-evolving, we hypothesized that satellite DNA turnover spurs adaptive evolution of DNA-protein crosslink repair beyond a single gene and beyond the D. melanogaster lineage. This hypothesis predicts pervasive Spartan gene family diversification across Drosophila species. To study the evolutionary history of the Drosophila Spartan gene family, we conducted population genetic, molecular evolution, phylogenomic, and tissue-specific expression analyses. We uncovered widespread signals of positive selection across multiple Spartan family genes and across multiple evolutionary timescales. We also detected recurrent Spartan family gene duplication, divergence, and gene loss. Finally, we found that ovary-enriched parent genes consistently birthed functionally diverged, testis-enriched daughter genes. To account for Spartan family diversification, we introduce a novel mechanistic model of antagonistic coevolution that links DNA satellite evolution and adaptive regulation of Spartan protease activity. This framework promises to accelerate our understanding of how DNA repeats drive recurrent evolutionary innovation to preserve genome integrity.
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Affiliation(s)
- Cara L Brand
- Department of Biology and Epigenetics Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Genevieve T Oliver
- Department of Biology and Epigenetics Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Isabella Z Farkas
- Department of Biology and Epigenetics Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Michael Buszczak
- Department of Molecular Biology and Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Mia T Levine
- Department of Biology and Epigenetics Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
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Hao H, Ren C, Lian Y, Zhao M, Bo T, Xu J, Wang W. Independent and Complementary Functions of Caf1b and Hir1 for Chromatin Assembly in Tetrahymena thermophila. Cells 2023; 12:2828. [PMID: 38132148 PMCID: PMC10741905 DOI: 10.3390/cells12242828] [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: 11/17/2023] [Revised: 12/09/2023] [Accepted: 12/11/2023] [Indexed: 12/23/2023] Open
Abstract
Histones and DNA associate to form the nucleosomes of eukaryotic chromatin. Chromatin assembly factor 1 (CAF-1) complex and histone regulatory protein A (HIRA) complex mediate replication-couple (RC) and replication-independent (RI) nucleosome assembly, respectively. CHAF1B and HIRA share a similar domain but play different roles in nucleosome assembly by binding to the different interactors. At present, there is limited understanding for the similarities and differences in their respective functions. Tetrahymena thermophila contains transcriptionally active polyploid macronuclei (MAC) and transcriptionally silent diploid micronuclei (MIC). Here, the distribution patterns of Caf1b and Hir1 exhibited both similarities and distinctions. Both proteins localized to the MAC and MIC during growth, and to the MIC during conjugation. However, Hir1 exhibited additional signaling on parental MAC and new MAC during sexual reproduction and displayed a punctate signal on developing anlagen. Caf1b and Hir1 only co-localized in the MIC with Pcna1 during conjugation. Knockdown of CAF1B impeded cellular growth and arrested sexual reproductive development. Loss of HIR1 led to MIC chromosome defects and aborted sexual development. Co-interference of CAF1B and HIR1 led to a more severe phenotype. Moreover, CAF1B knockdown led to the up-regulation of HIR1 expression, while knockdown of HIR1 also led to an increase in CAF1B expression. Furthermore, Caf1b and Hir1 interacted with different interactors. These results showed that CAF-1 and Hir1 have independent and complementary functions for chromatin assembly in T. thermophila.
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Affiliation(s)
- Huijuan Hao
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China; (H.H.); (C.R.); (Y.L.); (M.Z.); (T.B.)
| | - Chenhui Ren
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China; (H.H.); (C.R.); (Y.L.); (M.Z.); (T.B.)
| | - Yinjie Lian
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China; (H.H.); (C.R.); (Y.L.); (M.Z.); (T.B.)
| | - Min Zhao
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China; (H.H.); (C.R.); (Y.L.); (M.Z.); (T.B.)
| | - Tao Bo
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China; (H.H.); (C.R.); (Y.L.); (M.Z.); (T.B.)
| | - Jing Xu
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China; (H.H.); (C.R.); (Y.L.); (M.Z.); (T.B.)
- School of Life Science, Shanxi University, Taiyuan 030006, China
| | - Wei Wang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China; (H.H.); (C.R.); (Y.L.); (M.Z.); (T.B.)
- Shanxi Key Laboratory of Biotechnology, Taiyuan 030006, China
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7
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Nabeel-Shah S, Garg J, Ashraf K, Jeyapala R, Lee H, Petrova A, Burns JD, Pu S, Zhang Z, Greenblatt JF, Pearlman RE, Lambert JP, Fillingham J. Multilevel interrogation of H3.3 reveals a primordial role in transcription regulation. Epigenetics Chromatin 2023; 16:10. [PMID: 37024975 PMCID: PMC10080907 DOI: 10.1186/s13072-023-00484-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 03/28/2023] [Indexed: 04/08/2023] Open
Abstract
BACKGROUND Eukaryotic cells can rapidly adjust their transcriptional profile in response to molecular needs. Such dynamic regulation is, in part, achieved through epigenetic modifications and selective incorporation of histone variants into chromatin. H3.3 is the ancestral H3 variant with key roles in regulating chromatin states and transcription. Although H3.3 has been well studied in metazoans, information regarding the assembly of H3.3 onto chromatin and its possible role in transcription regulation remain poorly documented outside of Opisthokonts. RESULTS We used the nuclear dimorphic ciliate protozoan, Tetrahymena thermophila, to investigate the dynamics of H3 variant function in evolutionarily divergent eukaryotes. Functional proteomics and immunofluorescence analyses of H3.1 and H3.3 revealed a highly conserved role for Nrp1 and Asf1 histone chaperones in nuclear influx of histones. Cac2, a putative subunit of H3.1 deposition complex CAF1, is not required for growth, whereas the expression of the putative ortholog of the H3.3-specific chaperone Hir1 is essential in Tetrahymena. Our results indicate that Cac2 and Hir1 have distinct localization patterns during different stages of the Tetrahymena life cycle and suggest that Cac2 might be dispensable for chromatin assembly. ChIP-seq experiments in growing Tetrahymena show H3.3 enrichment over the promoters, gene bodies, and transcription termination sites of highly transcribed genes. H3.3 knockout followed by RNA-seq reveals large-scale transcriptional alterations in functionally important genes. CONCLUSION Our results provide an evolutionary perspective on H3.3's conserved role in maintaining the transcriptional landscape of cells and on the emergence of specialized chromatin assembly pathways.
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Affiliation(s)
- Syed Nabeel-Shah
- Department of Chemistry and Biology, Toronto Metropolitan University, 350 Victoria St, Toronto, M5B 2K3, Canada
- Donnelly Centre, University of Toronto, Toronto, M5S 3E1, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, M5S 1A8, Canada
| | - Jyoti Garg
- Department of Chemistry and Biology, Toronto Metropolitan University, 350 Victoria St, Toronto, M5B 2K3, Canada
- Department of Biology, York University, 4700 Keele St, Toronto, M3J 1P3, Canada
| | - Kanwal Ashraf
- Department of Biology, York University, 4700 Keele St, Toronto, M3J 1P3, Canada
| | - Renu Jeyapala
- Department of Chemistry and Biology, Toronto Metropolitan University, 350 Victoria St, Toronto, M5B 2K3, Canada
| | - Hyunmin Lee
- Donnelly Centre, University of Toronto, Toronto, M5S 3E1, Canada
- Department of Computer Science, University of Toronto, Toronto, M5S 1A8, Canada
| | - Alexandra Petrova
- Department of Chemistry and Biology, Toronto Metropolitan University, 350 Victoria St, Toronto, M5B 2K3, Canada
| | - James D Burns
- Donnelly Centre, University of Toronto, Toronto, M5S 3E1, Canada
| | - Shuye Pu
- Donnelly Centre, University of Toronto, Toronto, M5S 3E1, Canada
| | - Zhaolei Zhang
- Donnelly Centre, University of Toronto, Toronto, M5S 3E1, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, M5S 1A8, Canada
- Department of Computer Science, University of Toronto, Toronto, M5S 1A8, Canada
| | - Jack F Greenblatt
- Donnelly Centre, University of Toronto, Toronto, M5S 3E1, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, M5S 1A8, Canada
| | - Ronald E Pearlman
- Department of Biology, York University, 4700 Keele St, Toronto, M3J 1P3, Canada
| | - Jean-Philippe Lambert
- Department of Molecular Medicine, Cancer Research Center, Big Data Research Center, Université Laval, Quebec City, QC, Canada
- CHU de Québec Research Center, CHUL, 2705 Laurier Boulevard, Quebec City, QC, Canada
| | - Jeffrey Fillingham
- Department of Chemistry and Biology, Toronto Metropolitan University, 350 Victoria St, Toronto, M5B 2K3, Canada.
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8
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Sadeghi N, Boissonneault G, Tavalaee M, Nasr-Esfahani MH. Oxidative versus reductive stress: a delicate balance for sperm integrity. Syst Biol Reprod Med 2023; 69:20-31. [PMID: 36215401 DOI: 10.1080/19396368.2022.2119181] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Despite the long-standing notion of "oxidative stress," as the main mediator of many diseases including male infertility induced by increased reactive oxygen species (ROS), recent evidence suggests that ROS levels are also increased by "reductive stress," due to over-accumulation of reductants. Damaging mechanisms, like guanidine oxidation followed by DNA fragmentation, could be observed following reductive stress. Excessive accumulation of the reductants may arise from excess dietary supplementation over driving the one-carbon cycle and transsulfuration pathway, overproduction of NADPH through the pentose phosphate pathway (PPP), elevated levels of GSH leading to impaired mitochondrial oxidation, or as a result NADH accumulation. In addition, lower availability of oxidized reductants like NAD+, oxidized glutathione (GSSG), and oxidized thioredoxins (Trx-S2) induce electron leakage leading to the formation of hydrogen peroxide (H2O2). In addition, a lower level of NAD+ impairs poly (ADP-ribose) polymerase (PARP)-regulated DNA repair essential for proper chromatin integrity of sperm. Because of the limited studies regarding the possible involvement of reductive stress, antioxidant therapy remains a central approach in the treatment of male infertility. This review put forward the concept of reductive stress and highlights the potential role played by reductive vs oxidative stress at pre-and post-testicular levels and considering dietary supplementation.
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Affiliation(s)
- Niloofar Sadeghi
- Department of Biochemistry and Functional Genomics, Université de Sherbrooke, Sherbrooke, QC, Canada.,Department of Animal Biotechnology, Reproductive Biomedicine Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran
| | - Guylain Boissonneault
- Department of Biochemistry and Functional Genomics, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Marziyeh Tavalaee
- Department of Animal Biotechnology, Reproductive Biomedicine Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran
| | - Mohammad Hossein Nasr-Esfahani
- Department of Animal Biotechnology, Reproductive Biomedicine Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran
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9
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Fukuda Y, Akematsu T, Bando H, Kato K. Snf2 Proteins Are Required to Generate Gamete Pronuclei in Tetrahymena thermophila. Microorganisms 2022; 10:microorganisms10122426. [PMID: 36557679 PMCID: PMC9786623 DOI: 10.3390/microorganisms10122426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 12/03/2022] [Accepted: 12/05/2022] [Indexed: 12/13/2022] Open
Abstract
During sexual reproduction/conjugation of the ciliate Tetrahymena thermophila, the germinal micronucleus undergoes meiosis resulting in four haploid micronuclei (hMICs). All hMICs undergo post-meiotic DNA double-strand break (PM-DSB) formation, cleaving their genome. DNA lesions are subsequently repaired in only one ‘selected’ hMIC, which eventually produces gametic pronuclei. DNA repair in the selected hMIC involves chromatin remodeling by switching from the heterochromatic to the euchromatic state of its genome. Here, we demonstrate that, among the 15 Tetrahymena Snf2 family proteins, a core of the ATP-dependent chromatin remodeling complex in Tetrahymena, the germline nucleus specific Iswi in Tetrahymena IswiGTt and Rad5Tt is crucial for the generation of gametic pronuclei. In either gene knockout, the selected hMIC which shows euchromatin markers such as lysine-acetylated histone H3 does not appear, but all hMICs in which markers for DNA lesions persist are degraded, indicating that both IswiGTt and Rad5Tt have important roles in repairing PM-DSB DNA lesions and remodeling chromatin for the euchromatic state in the selected hMIC.
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Affiliation(s)
- Yasuhiro Fukuda
- Graduate School of Agricultural Science, Tohoku University, Osaki 989-6711, Miyagi, Japan
- Correspondence: ; Tel.: +81-229-84-7387
| | - Takahiko Akematsu
- Department of Biosciences, College of Humanities and Sciences, Nihon University, Tokyo 156-8550, Japan
| | - Hironori Bando
- Graduate School of Agricultural Science, Tohoku University, Osaki 989-6711, Miyagi, Japan
| | - Kentaro Kato
- Graduate School of Agricultural Science, Tohoku University, Osaki 989-6711, Miyagi, Japan
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10
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Feng Y, Neme R, Beh LY, Chen X, Braun J, Lu MW, Landweber LF. Comparative genomics reveals insight into the evolutionary origin of massively scrambled genomes. eLife 2022; 11:e82979. [PMID: 36421078 PMCID: PMC9797194 DOI: 10.7554/elife.82979] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 11/03/2022] [Indexed: 11/25/2022] Open
Abstract
Ciliates are microbial eukaryotes that undergo extensive programmed genome rearrangement, a natural genome editing process that converts long germline chromosomes into smaller gene-rich somatic chromosomes. Three well-studied ciliates include Oxytricha trifallax, Tetrahymena thermophila, and Paramecium tetraurelia, but only the Oxytricha lineage has a massively scrambled genome, whose assembly during development requires hundreds of thousands of precisely programmed DNA joining events, representing the most complex genome dynamics of any known organism. Here we study the emergence of such complex genomes by examining the origin and evolution of discontinuous and scrambled genes in the Oxytricha lineage. This study compares six genomes from three species, the germline and somatic genomes for Euplotes woodruffi, Tetmemena sp., and the model ciliate O. trifallax. We sequenced, assembled, and annotated the germline and somatic genomes of E. woodruffi, which provides an outgroup, and the germline genome of Tetmemena sp. We find that the germline genome of Tetmemena is as massively scrambled and interrupted as Oxytricha's: 13.6% of its gene loci require programmed translocations and/or inversions, with some genes requiring hundreds of precise gene editing events during development. This study revealed that the earlier diverged spirotrich, E. woodruffi, also has a scrambled genome, but only roughly half as many loci (7.3%) are scrambled. Furthermore, its scrambled genes are less complex, together supporting the position of Euplotes as a possible evolutionary intermediate in this lineage, in the process of accumulating complex evolutionary genome rearrangements, all of which require extensive repair to assemble functional coding regions. Comparative analysis also reveals that scrambled loci are often associated with local duplications, supporting a gradual model for the origin of complex, scrambled genomes via many small events of DNA duplication and decay.
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Affiliation(s)
- Yi Feng
- Departments of Biochemistry and Molecular Biophysics and Biological Sciences, Columbia UniversityNew YorkUnited States
| | - Rafik Neme
- Departments of Biochemistry and Molecular Biophysics and Biological Sciences, Columbia UniversityNew YorkUnited States
- Department of Chemistry and Biology, Universidad del NorteBarranquillaColombia
| | - Leslie Y Beh
- Departments of Biochemistry and Molecular Biophysics and Biological Sciences, Columbia UniversityNew YorkUnited States
| | - Xiao Chen
- Pacific BiosciencesMenlo ParkUnited States
| | - Jasper Braun
- Department of Mathematics and Statistics, University of South FloridaTampaUnited States
| | - Michael W Lu
- Departments of Biochemistry and Molecular Biophysics and Biological Sciences, Columbia UniversityNew YorkUnited States
| | - Laura F Landweber
- Departments of Biochemistry and Molecular Biophysics and Biological Sciences, Columbia UniversityNew YorkUnited States
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11
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Tian M, Cai X, Liu Y, Liucong M, Howard-Till R. A practical reference for studying meiosis in the model ciliate Tetrahymena thermophila. MARINE LIFE SCIENCE & TECHNOLOGY 2022; 4:595-608. [PMID: 37078080 PMCID: PMC10077211 DOI: 10.1007/s42995-022-00149-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Accepted: 09/28/2022] [Indexed: 05/03/2023]
Abstract
Meiosis is a critical cell division program that produces haploid gametes for sexual reproduction. Abnormalities in meiosis are often causes of infertility and birth defects (e.g., Down syndrome). Most organisms use a highly specialized zipper-like protein complex, the synaptonemal complex (SC), to guide and stabilize pairing of homologous chromosomes in meiosis. Although the SC is critical for meiosis in many eukaryotes, there are organisms that perform meiosis without a functional SC. However, such SC-less meiosis is poorly characterized. To understand the features of SC-less meiosis and its adaptive significance, the ciliated protozoan Tetrahymena was selected as a model. Meiosis research in Tetrahymena has revealed intriguing aspects of the regulatory programs utilized in its SC-less meiosis, yet additional efforts are needed for obtaining an in-depth comprehension of mechanisms that are associated with the absence of SC. Here, aiming at promoting a wider application of Tetrahymena for meiosis research, we introduce basic concepts and core techniques for studying meiosis in Tetrahymena and then suggest future directions for expanding the current Tetrahymena meiosis research toolbox. These methodologies could be adopted for dissecting meiosis in poorly characterized ciliates that might reveal novel features. Such data will hopefully provide insights into the function of the SC and the evolution of meiosis from a unique perspective. Supplementary Information The online version contains supplementary material available at 10.1007/s42995-022-00149-8.
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Affiliation(s)
- Miao Tian
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237 China
- Institute of Human Genetics, CNRS, University of Montpellier, 34090 Montpellier, France
| | - Xia Cai
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237 China
| | - Yujie Liu
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237 China
| | - Mingmei Liucong
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237 China
| | - Rachel Howard-Till
- Department of Molecular and Cellular Biology, University of California Davis, Davis, CA USA
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12
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Identification and utilization of a mutated 60S ribosomal subunit coding gene as an effective and cost-efficient selection marker for Tetrahymena genetic manipulation. Int J Biol Macromol 2022; 204:1-8. [PMID: 35122796 DOI: 10.1016/j.ijbiomac.2022.01.188] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/26/2022] [Accepted: 01/28/2022] [Indexed: 01/05/2023]
Abstract
Since the onset of molecular biology, the ciliate Tetrahymena thermophila has been one of the most convenient single-celled model eukaryotes for genetics, biochemistry, and cell biology. Particularly, thanks to the availability of several different selection markers, it is possible to knock out or knock in genes at multiple genetic loci simultaneously in Tetrahymena, which makes it an excellent model ciliate for tackling complex regulatory mechanisms. Despite these selection markers are efficient for genetic manipulation, the costly drugs used for selection have highlighted the urgent demand for an additional cost-efficient and effective selection marker. Here, we found that a mutated 60S ribosomal subunit component, RPL36A, confers T. thermophila with cycloheximide resistance. On top of that, we developed a cycloheximide cassette and explored suitable transformation and selection conditions. Using the new cassette, we obtained both knockout and knock-in strains successfully at a relatively low cost. This study also provided the first evidence that a cycloheximide resistance gene can be engineered as a selection marker to completely delete a gene from the highly-polyploid somatic nucleus in Tetrahymena.
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13
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Abstract
Piwi-bound small RNAs induce programmed DNA elimination in the ciliated protozoan Tetrahymena. Using the phenomenon called codeletion, this process can be reprogrammed to induce ectopic DNA elimination at basically any given genomic location. Here, we describe the usage of codeletion for genetic studies in Tetrahymena and for investigations of the molecular mechanism of Piwi-directed programmed DNA elimination.
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Affiliation(s)
- Salman Shehzada
- Institute of Human Genetics (IGH), CNRS and University of Montpellier, Montpellier, France
| | - Kazufumi Mochizuki
- Institute of Human Genetics (IGH), CNRS and University of Montpellier, Montpellier, France.
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14
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DNA Repair in Haploid Context. Int J Mol Sci 2021; 22:ijms222212418. [PMID: 34830299 PMCID: PMC8620282 DOI: 10.3390/ijms222212418] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 11/08/2021] [Accepted: 11/14/2021] [Indexed: 12/15/2022] Open
Abstract
DNA repair is a well-covered topic as alteration of genetic integrity underlies many pathological conditions and important transgenerational consequences. Surprisingly, the ploidy status is rarely considered although the presence of homologous chromosomes dramatically impacts the repair capacities of cells. This is especially important for the haploid gametes as they must transfer genetic information to the offspring. An understanding of the different mechanisms monitoring genetic integrity in this context is, therefore, essential as differences in repair pathways exist that differentiate the gamete’s role in transgenerational inheritance. Hence, the oocyte must have the most reliable repair capacity while sperm, produced in large numbers and from many differentiation steps, are expected to carry de novo variations. This review describes the main DNA repair pathways with a special emphasis on ploidy. Differences between Saccharomyces cerevisiae and Schizosaccharomyces pombe are especially useful to this aim as they can maintain a diploid and haploid life cycle respectively.
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15
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Lian Y, Hao H, Xu J, Bo T, Liang A, Wang W. The histone chaperone Nrp1 is required for chromatin stability and nuclear division in Tetrahymena thermophila. Epigenetics Chromatin 2021; 14:34. [PMID: 34301312 PMCID: PMC8299592 DOI: 10.1186/s13072-021-00409-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 07/06/2021] [Indexed: 12/23/2022] Open
Abstract
Histone chaperones facilitate DNA replication and repair by promoting chromatin assembly, disassembly and histone exchange. Following histones synthesis and nucleosome assembly, the histones undergo posttranslational modification by different enzymes and are deposited onto chromatins by various histone chaperones. In Tetrahymena thermophila, histones from macronucleus (MAC) and micronucleus (MIC) have been comprehensively investigated, but the function of histone chaperones remains unclear. Histone chaperone Nrp1 in Tetrahymena contains four conserved tetratricopepeptide repeat (TPR) domains and one C-terminal nuclear localization signal. TPR2 is typically interrupted by a large acidic motif. Immunofluorescence staining showed that Nrp1 is located in the MAC and MICs, but disappeared in the apoptotic parental MAC and the degraded MICs during the conjugation stage. Nrp1 was also colocalized with α-tubulin around the spindle structure. NRP1 knockdown inhibited cellular proliferation and led to the loss of chromosome, abnormal macronuclear amitosis, and disorganized micronuclear mitosis during the vegetative growth stage. During sexual developmental stage, the gametic nuclei failed to be selected and abnormally degraded in NRP1 knockdown mutants. Affinity purification combined with mass spectrometry analysis indicated that Nrp1 is co-purified with core histones, heat shock proteins, histone chaperones, and DNA damage repair proteins. The physical direct interaction of Nrp1 and Asf1 was also confirmed by pull-down analysis in vitro. The results show that histone chaperone Nrp1 is involved in micronuclear mitosis and macronuclear amitosis in the vegetative growth stage and maintains gametic nuclei formation during the sexual developmental stage. Nrp1 is required for chromatin stability and nuclear division in Tetrahymena thermophila.
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Affiliation(s)
- Yinjie Lian
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, 92 Wucheng Rd., Taiyuan, 030006, China
| | - Huijuan Hao
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, 92 Wucheng Rd., Taiyuan, 030006, China
| | - Jing Xu
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, 92 Wucheng Rd., Taiyuan, 030006, China.,School of Life Science, Shanxi University, Taiyuan, 030006, China
| | - Tao Bo
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, 92 Wucheng Rd., Taiyuan, 030006, China
| | - Aihua Liang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, 92 Wucheng Rd., Taiyuan, 030006, China
| | - Wei Wang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, 92 Wucheng Rd., Taiyuan, 030006, China.
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16
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Abstract
The presence of meiosis, which is a conserved component of sexual reproduction, across organisms from all eukaryotic kingdoms, strongly argues that sex is a primordial feature of eukaryotes. However, extant meiotic structures and processes can vary considerably between organisms. The ciliated protist Tetrahymena thermophila, which diverged from animals, plants, and fungi early in evolution, provides one example of a rather unconventional meiosis. Tetrahymena has a simpler meiosis compared with most other organisms: It lacks both a synaptonemal complex (SC) and specialized meiotic machinery for chromosome cohesion and has a reduced capacity to regulate meiotic recombination. Despite this, it also features several unique mechanisms, including elongation of the nucleus to twice the cell length to promote homologous pairing and prevent recombination between sister chromatids. Comparison of the meiotic programs of Tetrahymena and higher multicellular organisms may reveal how extant meiosis evolved from proto-meiosis.
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Affiliation(s)
- Josef Loidl
- Department of Chromosome Biology, Max Perutz Labs, University of Vienna, Vienna, Austria
- * E-mail:
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17
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Bergero R, Ellis P, Haerty W, Larcombe L, Macaulay I, Mehta T, Mogensen M, Murray D, Nash W, Neale MJ, O'Connor R, Ottolini C, Peel N, Ramsey L, Skinner B, Suh A, Summers M, Sun Y, Tidy A, Rahbari R, Rathje C, Immler S. Meiosis and beyond - understanding the mechanistic and evolutionary processes shaping the germline genome. Biol Rev Camb Philos Soc 2021; 96:822-841. [PMID: 33615674 PMCID: PMC8246768 DOI: 10.1111/brv.12680] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 12/15/2020] [Accepted: 12/15/2020] [Indexed: 12/11/2022]
Abstract
The separation of germ cell populations from the soma is part of the evolutionary transition to multicellularity. Only genetic information present in the germ cells will be inherited by future generations, and any molecular processes affecting the germline genome are therefore likely to be passed on. Despite its prevalence across taxonomic kingdoms, we are only starting to understand details of the underlying micro-evolutionary processes occurring at the germline genome level. These include segregation, recombination, mutation and selection and can occur at any stage during germline differentiation and mitotic germline proliferation to meiosis and post-meiotic gamete maturation. Selection acting on germ cells at any stage from the diploid germ cell to the haploid gametes may cause significant deviations from Mendelian inheritance and may be more widespread than previously assumed. The mechanisms that affect and potentially alter the genomic sequence and allele frequencies in the germline are pivotal to our understanding of heritability. With the rise of new sequencing technologies, we are now able to address some of these unanswered questions. In this review, we comment on the most recent developments in this field and identify current gaps in our knowledge.
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Affiliation(s)
- Roberta Bergero
- Institute of Evolutionary BiologyUniversity of EdinburghEdinburghEH9 3JTU.K.
| | - Peter Ellis
- School of BiosciencesUniversity of KentCanterburyCT2 7NJU.K.
| | | | - Lee Larcombe
- Applied Exomics LtdStevenage Bioscience CatalystStevenageSG1 2FXU.K.
| | - Iain Macaulay
- Earlham InstituteNorwich Research ParkNorwichNR4 7UZU.K.
| | - Tarang Mehta
- Earlham InstituteNorwich Research ParkNorwichNR4 7UZU.K.
| | - Mette Mogensen
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJU.K.
| | - David Murray
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJU.K.
| | - Will Nash
- Earlham InstituteNorwich Research ParkNorwichNR4 7UZU.K.
| | - Matthew J. Neale
- Genome Damage and Stability Centre, School of Life SciencesUniversity of SussexBrightonBN1 9RHU.K.
| | | | | | - Ned Peel
- Earlham InstituteNorwich Research ParkNorwichNR4 7UZU.K.
| | - Luke Ramsey
- The James Hutton InstituteInvergowrieDundeeDD2 5DAU.K.
| | - Ben Skinner
- School of Life SciencesUniversity of EssexColchesterCO4 3SQU.K.
| | - Alexander Suh
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJU.K.
- Department of Organismal BiologyUppsala UniversityNorbyvägen 18DUppsala752 36Sweden
| | - Michael Summers
- School of BiosciencesUniversity of KentCanterburyCT2 7NJU.K.
- The Bridge Centre1 St Thomas Street, London BridgeLondonSE1 9RYU.K.
| | - Yu Sun
- Norwich Medical SchoolUniversity of East AngliaNorwich Research Park, Colney LnNorwichNR4 7UGU.K.
| | - Alison Tidy
- School of BiosciencesUniversity of Nottingham, Plant Science, Sutton Bonington CampusSutton BoningtonLE12 5RDU.K.
| | | | - Claudia Rathje
- School of BiosciencesUniversity of KentCanterburyCT2 7NJU.K.
| | - Simone Immler
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJU.K.
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18
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Wahab S, Saettone A, Nabeel-Shah S, Dannah N, Fillingham J. Exploring the Histone Acetylation Cycle in the Protozoan Model Tetrahymena thermophila. Front Cell Dev Biol 2020; 8:509. [PMID: 32695779 PMCID: PMC7339932 DOI: 10.3389/fcell.2020.00509] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 05/28/2020] [Indexed: 12/22/2022] Open
Abstract
The eukaryotic histone acetylation cycle is composed of three classes of proteins, histone acetyltransferases (HATs) that add acetyl groups to lysine amino acids, bromodomain (BRD) containing proteins that are one of the most characterized of several protein domains that recognize acetyl-lysine (Kac) and effect downstream function, and histone deacetylases (HDACs) that catalyze the reverse reaction. Dysfunction of selected proteins of these three classes is associated with human disease such as cancer. Additionally, the HATs, BRDs, and HDACs of fungi and parasitic protozoa present potential drug targets. Despite their importance, the function and mechanisms of HATs, BRDs, and HDACs and how they relate to chromatin remodeling (CR) remain incompletely understood. Tetrahymena thermophila (Tt) provides a highly tractable single-celled free-living protozoan model for studying histone acetylation, featuring a massively acetylated somatic genome, a property that was exploited in the identification of the first nuclear/type A HAT Gcn5 in the 1990s. Since then, Tetrahymena remains an under-explored model for the molecular analysis of HATs, BRDs, and HDACs. Studies of HATs, BRDs, and HDACs in Tetrahymena have the potential to reveal the function of HATs and BRDs relevant to both fundamental eukaryotic biology and to the study of disease mechanisms in parasitic protozoa.
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Affiliation(s)
| | | | | | | | - Jeffrey Fillingham
- Department of Chemistry and Biology, Ryerson University, Toronto, ON, Canada
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19
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Cruz-Saavedra L, Vallejo GA, Guhl F, Ramírez JD. Transcriptomic changes across the life cycle of Trypanosoma cruzi II. PeerJ 2020; 8:e8947. [PMID: 32461822 PMCID: PMC7231504 DOI: 10.7717/peerj.8947] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 03/19/2020] [Indexed: 12/15/2022] Open
Abstract
Trypanosoma cruzi is a flagellated protozoan that causes Chagas disease; it presents a complex life cycle comprising four morphological stages: epimastigote (EP), metacyclic trypomastigote (MT), cell-derived trypomastigote (CDT) and amastigote (AM). Previous transcriptomic studies on three stages (EPs, CDTs and AMs) have demonstrated differences in gene expressions among them; however, to the best of our knowledge, no studies have reported on gene expressions in MTs. Therefore, the present study compared differentially expressed genes (DEGs), and signaling pathway reconstruction in EPs, MTs, AMs and CDTs. The results revealed differences in gene expressions in the stages evaluated; these differences were greater between MTs and AMs-PTs. The signaling pathway that presented the highest number of DEGs in all the stages was associated with ribosomes protein profiles, whereas the other related pathways activated were processes related to energy metabolism from glucose, amino acid metabolism, or RNA regulation. However, the role of autophagy in the entire life cycle of T. cruzi and the presence of processes such as meiosis and homologous recombination in MTs (where the expressions of SPO11 and Rad51 plays a role) are crucial. These findings represent an important step towards the full understanding of the molecular basis during the life cycle of T. cruzi.
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Affiliation(s)
- Lissa Cruz-Saavedra
- Grupo de Investigaciones Microbiológicas-UR (GIMUR), Departamento de Biología, Facultad de Ciencias Naturales, Universidad del Rosario, Bogota, Colombia
| | - Gustavo A Vallejo
- Laboratorio de Investigación en Parasitología Tropical, Facultad de Ciencias, Universidad del Tolima, Ibagué, Colombia
| | - Felipe Guhl
- Centro de Investigaciones en Microbiología y Parasitología Tropical (CIMPAT), Facultad de Ciencias, Universidad de Los Andes, Bogota, Colombia
| | - Juan David Ramírez
- Grupo de Investigaciones Microbiológicas-UR (GIMUR), Departamento de Biología, Facultad de Ciencias Naturales, Universidad del Rosario, Bogota, Colombia
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20
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Dokshin GA, Davis GM, Sawle AD, Eldridge MD, Nicholls PK, Gourley TE, Romer KA, Molesworth LW, Tatnell HR, Ozturk AR, de Rooij DG, Hannon GJ, Page DC, Mello CC, Carmell MA. GCNA Interacts with Spartan and Topoisomerase II to Regulate Genome Stability. Dev Cell 2020; 52:53-68.e6. [PMID: 31839538 PMCID: PMC7227305 DOI: 10.1016/j.devcel.2019.11.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 08/14/2019] [Accepted: 11/13/2019] [Indexed: 12/22/2022]
Abstract
GCNA proteins are expressed across eukarya in pluripotent cells and have conserved functions in fertility. GCNA homologs Spartan (DVC-1) and Wss1 resolve DNA-protein crosslinks (DPCs), including Topoisomerase-DNA adducts, during DNA replication. Here, we show that GCNA mutants in mouse and C. elegans display defects in genome maintenance including DNA damage, aberrant chromosome condensation, and crossover defects in mouse spermatocytes and spontaneous genomic rearrangements in C. elegans. We show that GCNA and topoisomerase II (TOP2) physically interact in both mice and worms and colocalize on condensed chromosomes during mitosis in C. elegans embryos. Moreover, C. elegans gcna-1 mutants are hypersensitive to TOP2 poison. Together, our findings support a model in which GCNA provides genome maintenance functions in the germline and may do so, in part, by promoting the resolution of TOP2 DPCs.
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Affiliation(s)
- Gregoriy A Dokshin
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Gregory M Davis
- School of Health and Life Sciences, Federation University, VIC 3841, Australia
| | - Ashley D Sawle
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, UK
| | - Matthew D Eldridge
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, UK
| | | | - Taylin E Gourley
- School of Health and Life Sciences, Federation University, VIC 3841, Australia
| | - Katherine A Romer
- Whitehead Institute, 455 Main Street, Cambridge, MA 02142, USA; Computational and Systems Biology Program, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Luke W Molesworth
- School of Health and Life Sciences, Federation University, VIC 3841, Australia
| | - Hannah R Tatnell
- School of Health and Life Sciences, Federation University, VIC 3841, Australia
| | - Ahmet R Ozturk
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Dirk G de Rooij
- Whitehead Institute, 455 Main Street, Cambridge, MA 02142, USA; Reproductive Biology Group, Division of Developmental Biology, Department of Biology, Faculty of Science, Utrecht University, Utrecht 3584, the Netherlands; Center for Reproductive Medicine, Academic Medical Center, University of Amsterdam 1105, the Netherlands
| | - Gregory J Hannon
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, UK; Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
| | - David C Page
- Whitehead Institute, 455 Main Street, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Whitehead Institute, Cambridge, MA 02142, USA
| | - Craig C Mello
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA 01605, USA; Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, MA 01605, USA.
| | - Michelle A Carmell
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA 01605, USA; Whitehead Institute, 455 Main Street, Cambridge, MA 02142, USA; Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
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21
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Akematsu T, Sánchez-Fernández R, Kosta F, Holzer E, Loidl J. The Transmembrane Protein Semi1 Positions Gamete Nuclei for Reciprocal Fertilization in Tetrahymena. iScience 2019; 23:100749. [PMID: 31884169 PMCID: PMC6941865 DOI: 10.1016/j.isci.2019.100749] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 11/01/2019] [Accepted: 11/25/2019] [Indexed: 11/01/2022] Open
Abstract
During sexual reproduction in the ciliate, Tetrahymena thermophila, cells of complementary mating type pair ("conjugate") undergo simultaneous meiosis and fertilize each other. In both mating partners only one of the four meiotic products is "selected" to escape autophagy, and this nucleus divides mitotically to produce two pronuclei. The migrating pronucleus of one cell translocates to the mating partner and fuses with its stationary pronucleus and vice versa. Selection of the designated gametic nucleus was thought to depend on its position within the cell because it always attaches to the junction with the partner cell. Here we show that a transmembrane protein, Semi1, is crucial for attachment. Loss of Semi1 causes failure to attach and consequent infertility. However, a nucleus is selected and gives rise to pronuclei regardless of Semi1 expression, indicating that attachment of a nucleus to the junction is not a precondition for selection but follows the selection process.
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Affiliation(s)
- Takahiko Akematsu
- Department of Chromosome Biology, University of Vienna, Dr. Bohr-Gasse 9, Vienna 1030, Austria.
| | | | - Felix Kosta
- Department of Chromosome Biology, University of Vienna, Dr. Bohr-Gasse 9, Vienna 1030, Austria
| | - Elisabeth Holzer
- Department of Chromosome Biology, University of Vienna, Dr. Bohr-Gasse 9, Vienna 1030, Austria
| | - Josef Loidl
- Department of Chromosome Biology, University of Vienna, Dr. Bohr-Gasse 9, Vienna 1030, Austria
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22
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Genetic and genomic evolution of sexual reproduction: echoes from LECA to the fungal kingdom. Curr Opin Genet Dev 2019; 58-59:70-75. [PMID: 31473482 DOI: 10.1016/j.gde.2019.07.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 06/28/2019] [Accepted: 07/16/2019] [Indexed: 12/30/2022]
Abstract
Sexual reproduction is vastly diverse and yet highly conserved across the eukaryotic domain. This ubiquity suggests that the last eukaryotic common ancestor (LECA) was sexual. It is hypothesized that several critical processes in sexual reproduction, including cell fusion and meiosis, were acquired during the evolution from the first eukaryotic common ancestor (FECA) to the sexual LECA. However, it is challenging to delineate the exact origin and evolution of sexual reproduction given that both FECA and LECA are extinct. Studies of diverse eukaryotes have helped to shed light on this sexual evolutionary trajectory, revealing that a primordial sexual ploidy cycle likely involved endoreplication followed by concerted chromosome loss and that cell-cell fusion, meiosis, and sex determination later arose to shape modern sexual reproduction. Despite the general conservation of sexual reproduction processes throughout eukaryotes, modern sexual cycles are immensely diverse and complex. This diversity and complexity has become readily apparent in the fungal kingdom with the recent rapid expansion of whole-genome sequencing. This abundance of data, the variety of genetic tools available to manipulate and characterize fungi, and the thorough characterization of many fungal sexual cycles make the fungal kingdom an excellent forum, in which to study the conservation and diversification of sexual reproduction.
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23
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Tian M, Mochizuki K, Loidl J. Non-coding RNA Transcription in Tetrahymena Meiotic Nuclei Requires Dedicated Mediator Complex-Associated Proteins. Curr Biol 2019; 29:2359-2370.e5. [PMID: 31280995 DOI: 10.1016/j.cub.2019.05.038] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 04/24/2019] [Accepted: 05/15/2019] [Indexed: 12/22/2022]
Abstract
To preserve genome integrity, eukaryotic cells use small RNA-directed mechanisms to repress transposable elements (TEs). Paradoxically, in order to silence TEs, precursors of the small RNAs must be transcribed from TEs. However, it is still poorly understood how these precursors are transcribed from TEs under silenced conditions. In the otherwise transcriptionally silent germline micronucleus (MIC) of Tetrahymena, a burst of non-coding RNA (ncRNA) transcription occurs during meiosis. The transcripts are processed into small RNAs that serve to identify TE-related sequences for elimination. The Mediator complex (Med) has an evolutionarily conserved role for transcription by bridging gene-specific transcription factors and RNA polymerase II. Here, we report that three Med-associated factors, Emit1, Emit2, and Rib1, are required for the biogenesis of small ncRNAs. Med localizes to the MIC only during meiosis, and both Med localization and MIC ncRNA transcription require Emit1 and Emit2. In the MIC, Med occupies TE-rich pericentromeric and telomeric regions in a Rib1-dependent manner. Rib1 is dispensable for ncRNA transcription but is required for the accumulation of double-stranded ncRNAs. Nuclear and sub-nuclear localization of the three Med-associated proteins is interdependent. Hence, Emit1 and Emit2 act coordinately to import Med into the MIC, and Rib1 recruits Med to specific chromosomal locations to quantitatively or qualitatively promote the biogenesis of functional ncRNA. Our results underscore that the transcription machinery can be regulated by a set of specialized Med-associated proteins to temporally transcribe TE-related sequences from a silent genome for small RNA biogenesis and genome defense.
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Affiliation(s)
- Miao Tian
- Department of Chromosome Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria.
| | - Kazufumi Mochizuki
- Institute of Human Genetics (IGH), CNRS, University of Montpellier, 34090 Montpellier, France
| | - Josef Loidl
- Department of Chromosome Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria
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Tian M, Loidl J. A chromatin-associated protein required for inducing and limiting meiotic DNA double-strand break formation. Nucleic Acids Res 2019; 46:11822-11834. [PMID: 30357385 PMCID: PMC6294514 DOI: 10.1093/nar/gky968] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 10/05/2018] [Indexed: 11/13/2022] Open
Abstract
Programmed DNA double-strand breaks (DSBs) are required for meiotic recombination, but the number is strictly controlled because they are potentially harmful. Here we report a novel protein, Pars11, which is required for Spo11-dependent DSB formation in the protist Tetrahymena. Pars11 localizes to chromatin early in meiotic prophase in a Spo11-independent manner and is removed before the end of prophase. Pars11 removal depends on DSB formation and ATR-dependent phosphorylation. In the absence of the DNA damage sensor kinase ATR, Pars11 is retained on chromatin and excess DSBs are generated. Similar levels of Pars11 persistence and DSB overproduction occur in a non-phosphorylatable pars11 mutant. We conclude that Pars11 supports DSB formation by Spo11 until enough DSBs are formed; thereafter, DSB production stops in response to ATR-dependent degradation of Pars11 or its removal from chromatin. A similar DSB control mechanism involving a Rec114-Tel1/ATM-dependent negative feedback loop regulates DSB formation in budding yeast. However, there is no detectable sequence homology between Pars11 and Rec114, and DSB numbers are more tightly controlled by Pars11 than by Rec114. The discovery of this mechanism for DSB regulation in the evolutionarily distant protist and fungal lineages suggests that it is conserved across eukaryotes.
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Affiliation(s)
- Miao Tian
- Department of Chromosome Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria
| | - Josef Loidl
- Department of Chromosome Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria
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25
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Saettone A, Nabeel-Shah S, Garg J, Lambert JP, Pearlman RE, Fillingham J. Functional Proteomics of Nuclear Proteins in Tetrahymena thermophila: A Review. Genes (Basel) 2019; 10:E333. [PMID: 31052454 PMCID: PMC6562869 DOI: 10.3390/genes10050333] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 04/23/2019] [Accepted: 04/25/2019] [Indexed: 12/14/2022] Open
Abstract
Identification and characterization of protein complexes and interactomes has been essential to the understanding of fundamental nuclear processes including transcription, replication, recombination, and maintenance of genome stability. Despite significant progress in elucidation of nuclear proteomes and interactomes of organisms such as yeast and mammalian systems, progress in other models has lagged. Protists, including the alveolate ciliate protozoa with Tetrahymena thermophila as one of the most studied members of this group, have a unique nuclear biology, and nuclear dimorphism, with structurally and functionally distinct nuclei in a common cytoplasm. These features have been important in providing important insights about numerous fundamental nuclear processes. Here, we review the proteomic approaches that were historically used as well as those currently employed to take advantage of the unique biology of the ciliates, focusing on Tetrahymena, to address important questions and better understand nuclear processes including chromatin biology of eukaryotes.
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Affiliation(s)
- Alejandro Saettone
- Department of Chemistry and Biology, Ryerson University, 350 Victoria Street, Toronto, ON M5B 2K3, Canada.
| | - Syed Nabeel-Shah
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, ON M5S 1A8, Canada.
| | - Jyoti Garg
- Department of Biology, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada.
| | - Jean-Philippe Lambert
- Department of Molecular Medicine and Cancer Research Centre, Université Laval, Quebec, QC, G1V 0A6, Canada.
- CHU de Québec Research Center, CHUL, 2705 Boulevard Laurier, Quebec, QC, G1V 4G2, Canada
| | - Ronald E Pearlman
- Department of Biology, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada.
| | - Jeffrey Fillingham
- Department of Chemistry and Biology, Ryerson University, 350 Victoria Street, Toronto, ON M5B 2K3, Canada.
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26
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Genetic Instability and Chromatin Remodeling in Spermatids. Genes (Basel) 2019; 10:genes10010040. [PMID: 30646585 PMCID: PMC6356297 DOI: 10.3390/genes10010040] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Revised: 01/04/2019] [Accepted: 01/08/2019] [Indexed: 12/13/2022] Open
Abstract
The near complete replacement of somatic chromatin in spermatids is, perhaps, the most striking nuclear event known to the eukaryotic domain. The process is far from being fully understood, but research has nevertheless unraveled its complexity as an expression of histone variants and post-translational modifications that must be finely orchestrated to promote the DNA topological change and compaction provided by the deposition of protamines. That this major transition may not be genetically inert came from early observations that transient DNA strand breaks were detected in situ at chromatin remodeling steps. The potential for genetic instability was later emphasized by our demonstration that a significant number of DNA double-strand breaks (DSBs) are formed and then repaired in the haploid context of spermatids. The detection of DNA breaks by 3'OH end labeling in the whole population of spermatids suggests that a reversible enzymatic process is involved, which differs from canonical apoptosis. We have set the stage for a better characterization of the genetic impact of this transition by showing that post-meiotic DNA fragmentation is conserved from human to yeast, and by providing tools for the initial mapping of the genome-wide DSB distribution in the mouse model. Hence, the molecular mechanism of post-meiotic DSB formation and repair in spermatids may prove to be a significant component of the well-known male mutation bias. Based on our recent observations and a survey of the literature, we propose that the chromatin remodeling in spermatids offers a proper context for the induction of de novo polymorphism and structural variations that can be transmitted to the next generation.
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27
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Zhu LS, Wang DQ, Cui K, Liu D, Zhu LQ. Emerging Perspectives on DNA Double-strand Breaks in Neurodegenerative Diseases. Curr Neuropharmacol 2019; 17:1146-1157. [PMID: 31362659 PMCID: PMC7057204 DOI: 10.2174/1570159x17666190726115623] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 06/03/2019] [Accepted: 07/01/2019] [Indexed: 11/22/2022] Open
Abstract
DNA double-strand breaks (DSBs) are common events that were recognized as one of the most toxic lesions in eukaryotic cells. DSBs are widely involved in many physiological processes such as V(D)J recombination, meiotic recombination, DNA replication and transcription. Deregulation of DSBs has been reported in multiple diseases in human beings, such as the neurodegenerative diseases, with which the underlying mechanisms are needed to be illustrated. Here, we reviewed the recent insights into the dysfunction of DSB formation and repair, contributing to the pathogenesis of neurodegenerative disorders including Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD) and ataxia telangiectasia (A-T).
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Affiliation(s)
| | | | | | | | - Ling-Qiang Zhu
- Address correspondence to this author at the Department of Neurosurgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, P.R. China; Tel: 862783692625; Fax: 862783692608; E-mail:
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28
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Grégoire MC, Leduc F, Morin MH, Cavé T, Arguin M, Richter M, Jacques PÉ, Boissonneault G. The DNA double-strand "breakome" of mouse spermatids. Cell Mol Life Sci 2018; 75:2859-2872. [PMID: 29417179 PMCID: PMC11105171 DOI: 10.1007/s00018-018-2769-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 01/14/2018] [Accepted: 02/01/2018] [Indexed: 12/19/2022]
Abstract
De novo germline mutations arise preferentially in male owing to fundamental differences between spermatogenesis and oogenesis. Post-meiotic chromatin remodeling in spermatids results in the elimination of most of the nucleosomal supercoiling and is characterized by transient DNA fragmentation. Using three alternative methods, DNA from sorted populations of mouse spermatids was used to confirm that double-strand breaks (DSB) are created in elongating spermatids and repaired at later steps. Specific capture of DSB was used for whole-genome mapping of DSB hotspots (breakome) for each population of differentiating spermatids. Hotspots are observed preferentially within introns and repeated sequences hence are more prevalent in the Y chromosome. When hotspots arise within genes, those involved in neurodevelopmental pathways become preferentially targeted reaching a high level of significance. Given the non-templated DNA repair in haploid spermatids, transient DSBs formation may, therefore, represent an important component of the male mutation bias and the etiology of neurological disorders, adding to the genetic variation provided by meiosis.
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Affiliation(s)
- Marie-Chantal Grégoire
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Frédéric Leduc
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Martin H Morin
- Department of Biology, Faculty of Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Tiphanie Cavé
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Mélina Arguin
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Martin Richter
- Department of Medicine, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Pierre-Étienne Jacques
- Department of Biology, Faculty of Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Guylain Boissonneault
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada.
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Abstract
Sex in social amoebae (or dictyostelids) has a number of striking features. Dictyostelid zygotes do not proliferate but grow to a large size by feeding on other cells of the same species, each zygote ultimately forming a walled structure called a macrocyst. The diploid macrocyst nucleus undergoes meiosis, after which a single meiotic product survives to restart haploid vegetative growth. Meiotic recombination is generally initiated by the Spo11 enzyme, which introduces DNA double-strand breaks. Uniquely, as far as is known among sexual eukaryotes, dictyostelids lack a SPO11 gene. Despite this, recombination occurs at high frequencies during meiosis in dictyostelids, through unknown mechanisms. The molecular processes underlying these events, and the evolutionary drivers that brought them into being, may shed light on the genetic conflicts that occur within and between genomes, and how they can be resolved.
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Noto T, Mochizuki K. Small RNA-Mediated trans-Nuclear and trans-Element Communications in Tetrahymena DNA Elimination. Curr Biol 2018; 28:1938-1949.e5. [DOI: 10.1016/j.cub.2018.04.071] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 04/17/2018] [Accepted: 04/19/2018] [Indexed: 10/14/2022]
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Resistance to 6-Methylpurine is Conferred by Defective Adenine Phosphoribosyltransferase in Tetrahymena. Genes (Basel) 2018; 9:genes9040179. [PMID: 29570682 PMCID: PMC5924521 DOI: 10.3390/genes9040179] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 03/16/2018] [Accepted: 03/20/2018] [Indexed: 02/05/2023] Open
Abstract
6-methylpurine (6mp) is a toxic analog of adenine that inhibits RNA and protein synthesis and interferes with adenine salvage mediated by adenine phosphoribosyltransferase (APRTase). Mutants of the ciliated protist Tetrahymena thermophila that are resistant to 6mp were isolated in 1974, but the mechanism of resistance has remained unknown. To investigate 6mp resistance in T. thermophila, we created 6mp-resistant strains and identified a mutation in the APRTase genomic locus (APRT1) that is responsible for 6mp resistance. While overexpression of the mutated APRT1 allele in 6mp-sensitive cells did not confer resistance to 6mp, reduced wild-type APRT1 expression resulted in a significant decrease in sensitivity to 6mp. Knocking out or reducing the expression of APRT1 by RNA interference (RNAi) did not affect robust cell growth, which indicates that adenine salvage is redundant or that de novo synthesis pathways provide sufficient adenosine monophosphate for viability. We also explored whether 6mp resistance could be used as a novel inducible selection marker by generating 6mp- and paromomycin-resistant double mutants. While 6mp- and paromomycin-resistant double mutants did express fluorescent proteins in an RNAi-based system, the system requires optimization before 6mp resistance can be used as an effective inducible selection marker.
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32
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Post-meiotic DNA double-strand breaks are conserved in fission yeast. Int J Biochem Cell Biol 2018; 98:24-28. [PMID: 29474927 DOI: 10.1016/j.biocel.2018.02.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 02/09/2018] [Accepted: 02/15/2018] [Indexed: 12/20/2022]
Abstract
In mammals, spermiogenesis is characterized by transient formation of DNA double-strand breaks (DSBs) in the whole population of haploid spermatids. DSB repair in such haploid context may represent a mutational transition. Using a combination of pulsed-field gel electrophoresis and specific labelling of DSBs at 3'OH DNA ends, we showed that post-meiotic, enzyme-induced DSBs are also observed in the synchronizable pat1-114 mutant of Shizosaccharomyces pombe as well as in a wild-type strain, while DNA repair is observed at later stages. This transient DNA fragmentation arises in the whole cell population and is seemingly independent of the caspase apoptotic pathway. Because histones are still present in spores, the transient DSBs do not require a major change in chromatin structure. These observations confirm the highly-conserved nature of the process in eukaryotes and provide a powerful model to study the underlying mechanism and its impact on the genetic landscape and adaptation.
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