1
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Sun S, Defosse T, Boyd A, Sop J, Verderose F, Surray D, Aziz M, Howland M, Wu S, Changela N, Jang J, Schindler K, Xing J, McKim KS. Whole transcriptome screening for novel genes involved in meiosis and fertility in Drosophila melanogaster. Sci Rep 2024; 14:3602. [PMID: 38351116 PMCID: PMC10864285 DOI: 10.1038/s41598-024-53346-z] [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: 05/30/2023] [Accepted: 01/31/2024] [Indexed: 02/16/2024] Open
Abstract
Reproductive success requires the development of viable oocytes and the accurate segregation of chromosomes during meiosis. Failure to segregate chromosomes properly can lead to infertility, miscarriages, or developmental disorders. A variety of factors contribute to accurate chromosome segregation and oocyte development, such as spindle assembly and sister chromatid cohesion. However, many proteins required for meiosis remain unknown. In this study, we aimed to develop a screening pipeline for identifying novel meiotic and fertility genes using the genome of Drosophila melanogaster. To accomplish this goal, genes upregulated within meiotically active tissues were identified. More than 240 genes with no known function were silenced using RNA interference (RNAi) and the effects on meiosis and fertility were assessed. We identified 94 genes that when silenced caused infertility and/or high levels of chromosomal nondisjunction. The vast majority of these genes have human and mouse homologs that are also poorly studied. Through this screening process, we identified novel genes that are crucial for meiosis and oocyte development but have not been extensively studied in human or model organisms. Understanding the function of these genes will be an important step towards the understanding of their biological significance during reproduction.
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Affiliation(s)
- Siqi Sun
- Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
| | - Tyler Defosse
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Ayla Boyd
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Joel Sop
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Faith Verderose
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Diya Surray
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Mark Aziz
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Margaret Howland
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Siwen Wu
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Neha Changela
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Janet Jang
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Karen Schindler
- Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
- Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, 145 Bevier Road, Piscataway, NJ, 08854, USA
| | - Jinchuan Xing
- Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
- Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, 145 Bevier Road, Piscataway, NJ, 08854, USA.
| | - Kim S McKim
- Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA.
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2
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Yadav AK, Polasek-Sedlackova H. Quantity and quality of minichromosome maintenance protein complexes couple replication licensing to genome integrity. Commun Biol 2024; 7:167. [PMID: 38336851 PMCID: PMC10858283 DOI: 10.1038/s42003-024-05855-w] [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: 10/05/2023] [Accepted: 01/25/2024] [Indexed: 02/12/2024] Open
Abstract
Accurate and complete replication of genetic information is a fundamental process of every cell division. The replication licensing is the first essential step that lays the foundation for error-free genome duplication. During licensing, minichromosome maintenance protein complexes, the molecular motors of DNA replication, are loaded to genomic sites called replication origins. The correct quantity and functioning of licensed origins are necessary to prevent genome instability associated with severe diseases, including cancer. Here, we delve into recent discoveries that shed light on the novel functions of licensed origins, the pathways necessary for their proper maintenance, and their implications for cancer therapies.
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Affiliation(s)
- Anoop Kumar Yadav
- Department of Cell Biology and Epigenetics, Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Hana Polasek-Sedlackova
- Department of Cell Biology and Epigenetics, Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic.
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3
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Hatoyama Y, Kanemaki MT. The assembly of the MCM2-7 hetero-hexamer and its significance in DNA replication. Biochem Soc Trans 2023:233028. [PMID: 37145026 DOI: 10.1042/bst20221465] [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: 02/17/2023] [Revised: 04/19/2023] [Accepted: 04/20/2023] [Indexed: 05/06/2023]
Abstract
The mini-chromosome maintenance proteins 2-7 (MCM2-7) hexamer is a protein complex that is key for eukaryotic DNA replication, which occurs only once per cell cycle. To achieve DNA replication, eukaryotic cells developed multiple mechanisms that control the timing of the loading of the hexamer onto chromatin and its activation as the replicative helicase. MCM2-7 is highly abundant in proliferating cells, which confers resistance to replication stress. Thus, the presence of an excess of MCM2-7 is important for maintaining genome integrity. However, the mechanism via which high MCM2-7 levels are achieved, other than the transcriptional upregulation of the MCM genes in the G1 phase, remained unknown. Recently, we and others reported that the MCM-binding protein (MCMBP) plays a role in the maintenance of high MCM2-7 levels and hypothesized that MCMBP functions as a chaperone in the assembly of the MCM2-7 hexamer. In this review, we discuss the roles of MCMBP in the control of MCM proteins and propose a model of the assembly of the MCM2-7 hexamer. Furthermore, we discuss a potential mechanism of the licensing checkpoint, which arrests the cells in the G1 phase when the levels of chromatin-bound MCM2-7 are reduced, and the possibility of targeting MCMBP as a chemotherapy for cancer.
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Affiliation(s)
- Yuki Hatoyama
- Department of Chromosome Science, National Institute of Genetics, Research Organization of Information and Systems (ROIS), Yata 1111, Mishima, Shizuoka 411-8540, Japan
- Graduate Institute for Advanced Studies, SOKENDAI, Yata 1111, Mishima, Shizuoka 411-8540, Japan
| | - Masato T Kanemaki
- Department of Chromosome Science, National Institute of Genetics, Research Organization of Information and Systems (ROIS), Yata 1111, Mishima, Shizuoka 411-8540, Japan
- Graduate Institute for Advanced Studies, SOKENDAI, Yata 1111, Mishima, Shizuoka 411-8540, Japan
- Department of Biological Science, The University of Tokyo, Tokyo 113-0033, Japan
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4
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Sun Z, Zhang J, Zeng F, Zhang S, Chai Z, Luo J, Cao J. Differentially Expressed mRNAs and Potential Mechanisms of
Radiation-Induced TUT4 −/− Esophageal Cell Injury. Dose Response 2022; 20:15593258221136810. [PMCID: PMC9620258 DOI: 10.1177/15593258221136810] [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: 05/07/2022] [Revised: 08/30/2022] [Accepted: 10/17/2022] [Indexed: 11/16/2022] Open
Abstract
Radiation-induced esophageal injury remains a limitation for the process of
radiotherapy for lung and esophageal cancer patients. Esophageal epithelial
cells are extremely sensitive to irradiation, nevertheless, factors involved in
the radiosensitivity of esophageal epithelial cells are still unknown. Terminal
uridyl transferase 4 (TUT4) could modify the sequence of miRNAs, which affect
their regulation on miRNA targets and function. In this study, we used
transcriptome sequencing technology to identify mRNAs that were differentially
expressed before and after radiotherapy in esophageal epithelial cells. We
further explored the mRNA expression profiles between wild-type and TUT4
knockout esophageal epithelial cells. Volcano and heatmap plots unsupervised
hierarchical clustering analysis were performed to classify the samples.
Enrichment analysis on Gene Ontology functional annotations and Kyoto
Encyclopedia of Genes and Genomes pathways was performed. We annotated
differential genes from metabolism, genetic information processing,
environmental information processing, cellular processes, and organismal systems
human diseases. The aberrantly expressed genes are significantly enriched in
irradiation-related biological processes, such as DNA replication, ferroptosis,
and cell cycle. Moreover, we explored the distribution of transcription factor
family and its target genes in differential genes. These mRNAs might serve as
therapeutic targets in TUT4-related radiation-induced esophageal injury.
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Affiliation(s)
- Zhiqiang Sun
- School of Radiation Medicine and
Protection,
Medical
College of Soochow University, Suzhou,
China,Collaborative Innovation Center of
Radiological Medicine of Jiangsu Higher Education
Institutions, Suzhou, China
| | - Jiaqi Zhang
- Department of
Radiotherapy,
The
Affiliated Changzhou No. 2 People’s Hospital of Nanjing Medical
University, Changzhou, China
| | - Fanye Zeng
- Second Department of Medical
Oncology,
The Fourth
Affiliated Hospital of Xinjiang Medical
University, Urumqi, China
| | - Shuyu Zhang
- School of Radiation Medicine and
Protection,
Medical
College of Soochow University, Suzhou,
China,Collaborative Innovation Center of
Radiological Medicine of Jiangsu Higher Education
Institutions, Suzhou, China
| | - Zhifang Chai
- School of Radiation Medicine and
Protection,
Medical
College of Soochow University, Suzhou,
China,Collaborative Innovation Center of
Radiological Medicine of Jiangsu Higher Education
Institutions, Suzhou, China
| | - Judong Luo
- Department of
Radiotherapy,
The
Affiliated Changzhou No. 2 People’s Hospital of Nanjing Medical
University, Changzhou, China,Judong Luo, Department of Radiotherapy, The
Affiliated Changzhou No.2 People’s Hospital of Nanjing Medical University,
Tianning District, Changzhou 213000, China.
| | - Jianping Cao
- School of Radiation Medicine and
Protection,
Medical
College of Soochow University, Suzhou,
China,Collaborative Innovation Center of
Radiological Medicine of Jiangsu Higher Education
Institutions, Suzhou, China
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5
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Saito Y, Santosa V, Ishiguro KI, Kanemaki MT. MCMBP promotes the assembly of the MCM2-7 hetero-hexamer to ensure robust DNA replication in human cells. eLife 2022; 11:77393. [PMID: 35438632 PMCID: PMC9018068 DOI: 10.7554/elife.77393] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2022] [Accepted: 04/08/2022] [Indexed: 12/26/2022] Open
Abstract
The MCM2–7 hetero-hexamer is the replicative DNA helicase that plays a central role in eukaryotic DNA replication. In proliferating cells, the expression level of the MCM2–7 hexamer is kept high, which safeguards the integrity of the genome. However, how the MCM2–7 hexamer is assembled in living cells remains unknown. Here, we revealed that the MCM-binding protein (MCMBP) plays a critical role in the assembly of this hexamer in human cells. MCMBP associates with MCM3 which is essential for maintaining the level of the MCM2–7 hexamer. Acute depletion of MCMBP demonstrated that it contributes to MCM2–7 assembly using nascent MCM3. Cells depleted of MCMBP gradually ceased to proliferate because of reduced replication licensing. Under this condition, p53-positive cells exhibited arrest in the G1 phase, whereas p53-null cells entered the S phase and lost their viability because of the accumulation of DNA damage, suggesting that MCMBP is a potential target for killing p53-deficient cancers.
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Affiliation(s)
- Yuichiro Saito
- Department of Chromosome Science, National Institute of Genetics, Research Organization of Information and Systems (ROIS), Mishima, Japan
| | - Venny Santosa
- Department of Chromosome Science, National Institute of Genetics, Research Organization of Information and Systems (ROIS), Mishima, Japan
| | - Kei-Ichiro Ishiguro
- Department of Chromosome Biology, Institute of Molecular Embryology and Genetics (IMEG), Kumamoto University, Kumamoto, Japan
| | - Masato T Kanemaki
- Department of Chromosome Science, National Institute of Genetics, Research Organization of Information and Systems (ROIS), Mishima, Japan.,Department of Genetics, The Graduate University for Advanced Studies (SOKENDAI), Mishima, Japan
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6
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Liffner B, Absalon S. Expansion Microscopy Reveals Plasmodium falciparum Blood-Stage Parasites Undergo Anaphase with A Chromatin Bridge in the Absence of Mini-Chromosome Maintenance Complex Binding Protein. Microorganisms 2021; 9:2306. [PMID: 34835432 PMCID: PMC8620465 DOI: 10.3390/microorganisms9112306] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 11/02/2021] [Accepted: 11/03/2021] [Indexed: 12/16/2022] Open
Abstract
The malaria parasite Plasmodium falciparum undergoes closed mitosis, which occurs within an intact nuclear envelope, and differs significantly from its human host. Mitosis is underpinned by the dynamics of microtubules and the nuclear envelope. To date, our ability to study P. falciparum mitosis by microscopy has been hindered by the small size of the P. falciparum nuclei. Ultrastructure expansion microscopy (U-ExM) has recently been developed for P. falciparum, allowing the visualization of mitosis at the individual nucleus level. Using U-ExM, three intranuclear microtubule structures are observed: hemispindles, mitotic spindles, and interpolar spindles. A previous study demonstrated that the mini-chromosome maintenance complex binding-protein (MCMBP) depletion caused abnormal nuclear morphology and microtubule defects. To investigate the role of microtubules following MCMBP depletion and study the nuclear envelope in these parasites, we developed the first nuclear stain enabled by U-ExM in P. falciparum. MCMBP-deficient parasites show aberrant hemispindles and mitotic spindles. Moreover, anaphase chromatin bridges and individual nuclei containing multiple microtubule structures were observed following MCMBP knockdown. Collectively, this study refines our understanding of MCMBP-deficient parasites and highlights the utility of U-ExM coupled with a nuclear envelope stain for studying mitosis in P. falciparum.
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Affiliation(s)
| | - Sabrina Absalon
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA;
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7
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Shastri VM, Subramanian V, Schmidt KH. A novel cell-cycle-regulated interaction of the Bloom syndrome helicase BLM with Mcm6 controls replication-linked processes. Nucleic Acids Res 2021; 49:8699-8713. [PMID: 34370039 PMCID: PMC8421143 DOI: 10.1093/nar/gkab663] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 07/16/2021] [Accepted: 07/22/2021] [Indexed: 11/13/2022] Open
Abstract
The Bloom syndrome DNA helicase BLM contributes to chromosome stability through its roles in double-strand break repair by homologous recombination and DNA replication fork restart during the replication stress response. Loss of BLM activity leads to Bloom syndrome, which is characterized by extraordinary cancer risk and small stature. Here, we have analyzed the composition of the BLM complex during unperturbed S-phase and identified a direct physical interaction with the Mcm6 subunit of the minichromosome maintenance (MCM) complex. Using distinct binding sites, BLM interacts with the N-terminal domain of Mcm6 in G1 phase and switches to the C-terminal Cdt1-binding domain of Mcm6 in S-phase, with a third site playing a role for Mcm6 binding after DNA damage. Disruption of Mcm6-binding to BLM in S-phase leads to supra-normal DNA replication speed in unperturbed cells, and the helicase activity of BLM is required for this increased replication speed. Upon disruption of BLM/Mcm6 interaction, repair of replication-dependent DNA double-strand breaks is delayed and cells become hypersensitive to DNA damage and replication stress. Our findings reveal that BLM not only plays a role in the response to DNA damage and replication stress, but that its physical interaction with Mcm6 is required in unperturbed cells, most notably in S-phase as a negative regulator of replication speed.
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Affiliation(s)
- Vivek M Shastri
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, FL 33620, USA
| | - Veena Subramanian
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, FL 33620, USA
| | - Kristina H Schmidt
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, FL 33620, USA.,Cancer Biology and Evolution Program, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL 33612, USA
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8
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Absalon S, Dvorin JD. Depletion of the mini-chromosome maintenance complex binding protein allows the progression of cytokinesis despite abnormal karyokinesis during the asexual development of Plasmodium falciparum. Cell Microbiol 2020; 23:e13284. [PMID: 33124706 DOI: 10.1111/cmi.13284] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 10/22/2020] [Accepted: 10/26/2020] [Indexed: 12/23/2022]
Abstract
The eukaryotic cell cycle is typically divided into distinct phases with cytokinesis immediately following mitosis. To ensure proper cell division, each phase is tightly coordinated via feedback controls named checkpoints. During its asexual replication cycle, the malaria parasite Plasmodium falciparum undergoes multiple asynchronous rounds of mitosis with segregation of uncondensed chromosomes followed by nuclear division with intact nuclear envelope. The multi-nucleated schizont is then subjected to a single round of cytokinesis that produces dozens of daughter cells called merozoites. To date, no cell cycle checkpoints have been identified that regulate the Plasmodium spp. mode of division. Here, we identify the Plasmodium homologue of the Mini-Chromosome Maintenance Complex Binding Protein (PfMCMBP), which co-purified with the Mini-Chromosome Maintenance (MCM) complex, a replicative helicase required for genomic DNA replication. By conditionally depleting PfMCMBP, we disrupt nuclear morphology and parasite proliferation without causing a block in DNA replication. By immunofluorescence microscopy, we show that PfMCMBP depletion promotes the formation of mitotic spindle microtubules with extensions to more than one DNA focus and abnormal centrin distribution. Strikingly, PfMCMBP-deficient parasites complete cytokinesis and form aneuploid merozoites with variable cellular and nuclear sizes. Our study demonstrates that the parasite lacks a robust checkpoint response to prevent cytokinesis following aberrant karyokinesis.
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Affiliation(s)
- Sabrina Absalon
- Division of Infectious Diseases, Boston Children's Hospital, Boston, Massachusetts, USA.,Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Jeffrey D Dvorin
- Division of Infectious Diseases, Boston Children's Hospital, Boston, Massachusetts, USA.,Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA
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9
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Sedlackova H, Rask MB, Gupta R, Choudhary C, Somyajit K, Lukas J. Equilibrium between nascent and parental MCM proteins protects replicating genomes. Nature 2020; 587:297-302. [PMID: 33087936 DOI: 10.1038/s41586-020-2842-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 07/27/2020] [Indexed: 12/14/2022]
Abstract
Minichromosome maintenance proteins (MCMs) are DNA-dependent ATPases that bind to replication origins and license them to support a single round of DNA replication. A large excess of MCM2-7 assembles on chromatin in G1 phase as pre-replication complexes (pre-RCs), of which only a fraction become the productive CDC45-MCM-GINS (CMG) helicases that are required for genome duplication1-4. It remains unclear why cells generate this surplus of MCMs, how they manage to sustain it across multiple generations, and why even a mild reduction in the MCM pool compromises the integrity of replicating genomes5,6. Here we show that, for daughter cells to sustain error-free DNA replication, their mother cells build up a nuclear pool of MCMs both by recycling chromatin-bound (parental) MCMs and by synthesizing new (nascent) MCMs. Although all MCMs can form pre-RCs, it is the parental pool that is inherently stable and preferentially matures into CMGs. By contrast, nascent MCM3-7 (but not MCM2) undergo rapid proteolysis in the cytoplasm, and their stabilization and nuclear translocation require interaction with minichromosome-maintenance complex-binding protein (MCMBP), a distant MCM paralogue7,8. By chaperoning nascent MCMs, MCMBP safeguards replicating genomes by increasing chromatin coverage with pre-RCs that do not participate on replication origins but adjust the pace of replisome movement to minimize errors during DNA replication. Consequently, although the paucity of pre-RCs in MCMBP-deficient cells does not alter DNA synthesis overall, it increases the speed and asymmetry of individual replisomes, which leads to DNA damage. The surplus of MCMs therefore increases the robustness of genome duplication by restraining the speed at which eukaryotic cells replicate their DNA. Alterations in physiological fork speed might thus explain why even a minor reduction in MCM levels destabilizes the genome and predisposes to increased incidence of tumour formation.
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Affiliation(s)
- Hana Sedlackova
- Protein Signaling Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Maj-Britt Rask
- Protein Signaling Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Rajat Gupta
- Proteomics Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Chunaram Choudhary
- Proteomics Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kumar Somyajit
- Protein Signaling Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
| | - Jiri Lukas
- Protein Signaling Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
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10
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Jang SM, Redon CE, Thakur BL, Bahta MK, Aladjem MI. Regulation of cell cycle drivers by Cullin-RING ubiquitin ligases. Exp Mol Med 2020; 52:1637-1651. [PMID: 33005013 PMCID: PMC8080560 DOI: 10.1038/s12276-020-00508-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 08/10/2020] [Indexed: 12/11/2022] Open
Abstract
The last decade has revealed new roles for Cullin-RING ubiquitin ligases (CRLs) in a myriad of cellular processes, including cell cycle progression. In addition to CRL1, also named SCF (SKP1-Cullin 1-F box protein), which has been known for decades as an important factor in the regulation of the cell cycle, it is now evident that all eight CRL family members are involved in the intricate cellular pathways driving cell cycle progression. In this review, we summarize the structure of CRLs and their functions in driving the cell cycle. We focus on how CRLs target key proteins for degradation or otherwise alter their functions to control the progression over the various cell cycle phases leading to cell division. We also summarize how CRLs and the anaphase-promoting complex/cyclosome (APC/C) ligase complex closely cooperate to govern efficient cell cycle progression.
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Affiliation(s)
- Sang-Min Jang
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, 20892-4255, USA.
| | - Christophe E Redon
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, 20892-4255, USA
| | - Bhushan L Thakur
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, 20892-4255, USA
| | - Meriam K Bahta
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, 20892-4255, USA
| | - Mirit I Aladjem
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, 20892-4255, USA.
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11
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Limas JC, Cook JG. Preparation for DNA replication: the key to a successful S phase. FEBS Lett 2019; 593:2853-2867. [PMID: 31556113 DOI: 10.1002/1873-3468.13619] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 09/09/2019] [Accepted: 09/17/2019] [Indexed: 12/13/2022]
Abstract
Successful genome duplication is required for cell proliferation and demands extraordinary precision and accuracy. The mechanisms by which cells enter, progress through, and exit S phase are intense areas of focus in the cell cycle and genome stability fields. Key molecular events in the G1 phase of the cell division cycle, especially origin licensing, are essential for pre-establishing conditions for efficient DNA replication during the subsequent S phase. If G1 events are poorly regulated or disordered, then DNA replication can be compromised leading to genome instability, a hallmark of tumorigenesis. Upon entry into S phase, coordinated origin firing and replication progression ensure complete, timely, and precise chromosome replication. Both G1 and S phase progressions are controlled by master cell cycle protein kinases and ubiquitin ligases that govern the activity and abundance of DNA replication factors. In this short review, we describe current understanding and recent developments related to G1 progression and S phase entrance and exit with a particular focus on origin licensing regulation in vertebrates.
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Affiliation(s)
- Juanita C Limas
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC, USA
| | - Jeanette Gowen Cook
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC, USA.,Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, NC, USA
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12
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Minichromosomal Maintenance Component Complex 5 (MCM5) as a Marker of Barrett's Esophagus-Related Neoplasia: A Feasibility Study. Dig Dis Sci 2019; 64:2815-2822. [PMID: 30982210 DOI: 10.1007/s10620-019-05607-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Accepted: 03/27/2019] [Indexed: 01/10/2023]
Abstract
BACKGROUND The endoscopic detection of esophageal cancer is suboptimal in both patients referred with dyspeptic symptoms and those enrolled in Barrett's surveillance programs. MCM5 expression in cells collected from gastric fluid may be correlated with the presence of dysplasia or adenocarcinoma. Analysis of this biomarker may improve the detection of cancer. METHODS Sixty-one patients were enrolled at a single UK referral center. From each patient, 5-10 ml of gastric fluid was aspirated endoscopically. Patients were categorized according to their histology, normal, non-dysplastic Barrett's (NDBE), high-grade dysplastic Barrett's (HGD), and esophageal adenocarcinoma (EAC). All histology was confirmed by Seattle protocol biopsies or endoscopic mucosal resection. Samples were centrifuged, and the cell pellet was lysed. MCM5 expression levels were quantified using a proprietary immunoassay. The mean MCM5 expression was compared between groups by Kruskal-Wallis test. ROC curves were also used to assess diagnostic utility. RESULTS The mean expression of MCM5 increases as patients progress from a normal esophagus to NDBE, HGD, and EAC (14.4; 49.8; 112.3; and 154.1, respectively). There was a significant difference in the MCM5 expression of patients with a normal esophagus compared to those with EAC (p = 0.04). There was a trend toward higher MCM5 expression in patients with EAC compared to those with NDBE (p = 0.34). MCM5 expression was a fair discriminator (AUC 0.70 [95% CI 0.57-0.83]) between patients without neoplasia (normal and NDBE) and those with early neoplasia (HGD and EAC). CONCLUSION MCM5 expression in gastric fluid samples can differentiate patients with a histologically normal esophagus compared to those with early adenocarcinoma. Larger, powered studies are needed to assess whether it can be used to differentiate those with HGD from NDBE.
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13
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Kim HS. Genome-wide function of MCM-BP in Trypanosoma brucei DNA replication and transcription. Nucleic Acids Res 2019; 47:634-647. [PMID: 30407533 PMCID: PMC6344857 DOI: 10.1093/nar/gky1088] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 10/21/2018] [Indexed: 12/13/2022] Open
Abstract
In Trypanosoma brucei, genes are arranged in Polycistronic Transcription Units (PTUs), which are demarcated by transcription start and stop sites. Transcription start sites are also binding sites of Origin Recognition Complex 1 (ORC1). This spatial coincidence implies that transcription and replication in trypanosomes must occur in a highly ordered and cooperative manner. Interestingly, a previously published genetic screen identified the T. brucei MCM-BP, which interacts with subunits of MCM helicase, as a protein whose downregulation results in the loss of transcriptional silencing at subtelomeric loci. Here, I show that TbMCM-BP is required for DNA replication and transcription. TbMCM-BP depletion causes a significant reduction of replicating cells in S phase and genome-wide impairments of replication origin activation. Moreover, levels of sense and antisense transcripts increase at boundaries of PTUs in the absence of TbMCM-BP. TbMCM-BP is also important for transcriptional repression of the specialized subtelomeric PTUs, the Bloodstream-form Expression-Sites (BESs), which house the major antigenic determinant (the Variant Surface Glycoprotein, VSG gene) as well as TbORC1 binding sites. Overall, this study reveals that TbMCM-BP, a replication initiation protein, also guides the initiation, termination and directionality of transcription.
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Affiliation(s)
- Hee-Sook Kim
- Laboratory of Lymphocyte Biology, Rockefeller University, 1275 York Avenue, New York, NY 10065, USA.,Department of Biological, Geological, and Environmental Sciences, Center for Gene Regulation in Health and Disease, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
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14
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Whalen DS, Widatalla SE, Korolkova OY, Nangami GS, Beasley HK, Williams SD, Virgous C, Lehmann BD, Ochieng J, Sakwe AM. Implication of calcium activated RasGRF2 in Annexin A6-mediated breast tumor cell growth and motility. Oncotarget 2019; 10:133-151. [PMID: 30719209 PMCID: PMC6349432 DOI: 10.18632/oncotarget.26512] [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: 07/25/2015] [Accepted: 12/16/2018] [Indexed: 01/10/2023] Open
Abstract
The role of AnxA6 in breast cancer and in particular, the mechanisms underlying its contribution to tumor cell growth and/or motility remain poorly understood. In this study, we established the tumor suppressor function of AnxA6 in triple negative breast cancer (TNBC) cells by showing that loss of AnxA6 is associated with early onset and rapid growth of xenograft TNBC tumors in mice. We also identified the Ca2+ activated RasGRF2 as an effector of AnxA6 mediated TNBC cell growth and motility. Activation of Ca2+ mobilizing oncogenic receptors such as epidermal growth factor receptor (EGFR) in TNBC cells or pharmacological stimulation of Ca2+ influx led to activation, subsequent degradation and altered effector functions of RasGRF2. Inhibition of Ca2+ influx or overexpression of AnxA6 blocked the activation/degradation of RasGRF2. We also show that AnxA6 acts as a scaffold for RasGRF2 and Ras proteins and that its interaction with RasGRF2 is modulated by GTP and/or activation of Ras proteins. Meanwhile, down-regulation of RasGRF2 and treatment of cells with the EGFR-targeted tyrosine kinase inhibitor (TKI) lapatinib strongly attenuated the growth of otherwise EGFR-TKI resistant AnxA6 high TNBC cells. These data not only suggest that AnxA6 modulated Ca2+ influx and effector functions of RasGRF2 underlie at least in part, the AnxA6 mediated TNBC cell growth and/or motility, but also provide a rationale to target Ras-driven TNBC with EGFR targeted therapies in combination with inhibition of RasGRF2.
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Affiliation(s)
- Diva S Whalen
- Department of Biochemistry and Cancer Biology, School of Graduate Studies and Research, Meharry Medical College, Nashville, TN, USA
| | - Sarrah E Widatalla
- Department of Biochemistry and Cancer Biology, School of Graduate Studies and Research, Meharry Medical College, Nashville, TN, USA
| | - Olga Y Korolkova
- Department of Biochemistry and Cancer Biology, School of Graduate Studies and Research, Meharry Medical College, Nashville, TN, USA
| | - Gladys S Nangami
- Department of Biochemistry and Cancer Biology, School of Graduate Studies and Research, Meharry Medical College, Nashville, TN, USA
| | - Heather K Beasley
- Department of Biochemistry and Cancer Biology, School of Graduate Studies and Research, Meharry Medical College, Nashville, TN, USA
| | - Stephen D Williams
- Department of Biochemistry and Cancer Biology, School of Graduate Studies and Research, Meharry Medical College, Nashville, TN, USA
| | - Carlos Virgous
- Animal Care Facility, Meharry Medical College, Nashville, TN, USA
| | - Brian D Lehmann
- Department of Biochemistry, Vanderbilt University, Nashville, TN, USA
| | - Josiah Ochieng
- Department of Biochemistry and Cancer Biology, School of Graduate Studies and Research, Meharry Medical College, Nashville, TN, USA
| | - Amos M Sakwe
- Department of Biochemistry and Cancer Biology, School of Graduate Studies and Research, Meharry Medical College, Nashville, TN, USA
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15
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Leturcq M, Mortuaire M, Hardivillé S, Schulz C, Lefebvre T, Vercoutter-Edouart AS. O-GlcNAc transferase associates with the MCM2-7 complex and its silencing destabilizes MCM-MCM interactions. Cell Mol Life Sci 2018; 75:4321-4339. [PMID: 30069701 PMCID: PMC6208770 DOI: 10.1007/s00018-018-2874-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 07/06/2018] [Accepted: 07/13/2018] [Indexed: 02/07/2023]
Abstract
O-GlcNAcylation of proteins is governed by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). The homeostasis of O-GlcNAc cycling is regulated during cell cycle progression and is essential for proper cellular division. We previously reported the O-GlcNAcylation of the minichromosome maintenance proteins MCM2, MCM3, MCM6 and MCM7. These proteins belong to the MCM2-7 complex which is crucial for the initiation of DNA replication through its DNA helicase activity. Here we show that the six subunits of MCM2-7 are O-GlcNAcylated and that O-GlcNAcylation of MCM proteins mainly occurs in the chromatin-bound fraction of synchronized human cells. Moreover, we identify stable interaction between OGT and several MCM subunits. We also show that down-regulation of OGT decreases the chromatin binding of MCM2, MCM6 and MCM7 without affecting their steady-state level. Finally, OGT silencing or OGA inhibition destabilizes MCM2/6 and MCM4/7 interactions in the chromatin-enriched fraction. In conclusion, OGT is a new partner of the MCM2-7 complex and O-GlcNAcylation homeostasis might regulate MCM2-7 complex by regulating the chromatin loading of MCM6 and MCM7 and stabilizing MCM/MCM interactions.
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Affiliation(s)
- Maïté Leturcq
- Univ. Lille, CNRS, UMR 8576, UGSF, Unité de Glycobiologie Structurale et Fonctionnelle, 59000, Lille, France
| | - Marlène Mortuaire
- Univ. Lille, CNRS, UMR 8576, UGSF, Unité de Glycobiologie Structurale et Fonctionnelle, 59000, Lille, France
| | - Stéphan Hardivillé
- Univ. Lille, CNRS, UMR 8576, UGSF, Unité de Glycobiologie Structurale et Fonctionnelle, 59000, Lille, France
| | - Céline Schulz
- Univ. Lille, CNRS, UMR 8576, UGSF, Unité de Glycobiologie Structurale et Fonctionnelle, 59000, Lille, France
| | - Tony Lefebvre
- Univ. Lille, CNRS, UMR 8576, UGSF, Unité de Glycobiologie Structurale et Fonctionnelle, 59000, Lille, France
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16
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Tamberg N, Tahk S, Koit S, Kristjuhan K, Kasvandik S, Kristjuhan A, Ilves I. Keap1-MCM3 interaction is a potential coordinator of molecular machineries of antioxidant response and genomic DNA replication in metazoa. Sci Rep 2018; 8:12136. [PMID: 30108253 PMCID: PMC6092318 DOI: 10.1038/s41598-018-30562-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 08/02/2018] [Indexed: 01/19/2023] Open
Abstract
Coordination of DNA replication and cellular redox homeostasis mechanisms is essential for the sustained genome stability due to the sensitivity of replicating DNA to oxidation. However, substantial gaps remain in our knowledge of underlying molecular pathways. In this study, we characterise the interaction of Keap1, a central antioxidant response regulator in Metazoa, with the replicative helicase subunit protein MCM3. Our analysis suggests that structural determinants of the interaction of Keap1 with its critical downstream target - Nrf2 master transactivator of oxidative stress response genes – may have evolved in evolution to mimic the conserved helix-2-insert motif of MCM3. We show that this has led to a competition between MCM3 and Nrf2 proteins for Keap1 binding, and likely recruited MCM3 for the competitive binding dependent modulation of Keap1 controlled Nrf2 activities. We hypothesise that such mechanism could help to adjust the Keap1-Nrf2 antioxidant response pathway according to the proliferative and replicative status of the cell, with possible reciprocal implications also for the regulation of cellular functions of MCM3. Altogether this suggests about important role of Keap1-MCM3 interaction in the cross-talk between replisome and redox homeostasis machineries in metazoan cells.
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Affiliation(s)
- Nele Tamberg
- Institute of Technology, University of Tartu, Tartu, 50411, Estonia
| | - Siret Tahk
- Institute of Technology, University of Tartu, Tartu, 50411, Estonia
| | - Sandra Koit
- Institute of Technology, University of Tartu, Tartu, 50411, Estonia
| | - Kersti Kristjuhan
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, 51010, Estonia
| | - Sergo Kasvandik
- Institute of Technology, University of Tartu, Tartu, 50411, Estonia
| | - Arnold Kristjuhan
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, 51010, Estonia
| | - Ivar Ilves
- Institute of Technology, University of Tartu, Tartu, 50411, Estonia.
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17
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Affinity Purification-Mass Spectroscopy Methods for Identifying Epstein-Barr Virus-Host Interactions. Methods Mol Biol 2017; 1532:79-92. [PMID: 27873268 DOI: 10.1007/978-1-4939-6655-4_5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Considerable insight into the function and mechanism of action of viral proteins has come from identifying the cellular proteins with which they interact. In recent years, mass spectrometry-based methods have emerged as the method of choice for protein interaction discovery due to their comprehensive and unbiased nature. Methods involving single affinity purifications of epitope-tagged viral proteins (AP-MS) and tandem affinity purifications of viral proteins with two purification tags (TAP tagging) have both been used to identify novel host interactions with EBV proteins. However, to date these methods have only been applied to a small number of EBV proteins. Here we provide detailed methods of AP-MS and TAP tagging approaches that can be applied to any EBV protein in order to discover its host interactions.
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18
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Breitkopf SB, Yuan M, Helenius KP, Lyssiotis CA, Asara JM. Triomics Analysis of Imatinib-Treated Myeloma Cells Connects Kinase Inhibition to RNA Processing and Decreased Lipid Biosynthesis. Anal Chem 2015; 87:10995-1006. [PMID: 26434776 PMCID: PMC5585869 DOI: 10.1021/acs.analchem.5b03040] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The combination of metabolomics, lipidomics, and phosphoproteomics that incorporates triple stable isotope labeling by amino acids in cell culture (SILAC) protein labeling, as well as (13)C in vivo metabolite labeling, was demonstrated on BCR-ABL-positive H929 multiple myeloma cells. From 11 880 phosphorylation sites, we confirm that H929 cells are primarily signaling through the BCR-ABL-ERK pathway, and we show that imatinib treatment not only downregulates phosphosites in this pathway but also upregulates phosphosites on proteins involved in RNA expression. Metabolomics analyses reveal that BCR-ABL-ERK signaling in H929 cells drives the pentose phosphate pathway (PPP) and RNA biosynthesis, where pathway inhibition via imatinib results in marked PPP impairment and an accumulation of RNA nucleotides and negative regulation of mRNA. Lipidomics data also show an overall reduction in lipid biosynthesis and fatty acid incorporation with a significant decrease in lysophospholipids. RNA immunoprecipitation studies confirm that RNA degradation is inhibited with short imatinib treatment and transcription is inhibited upon long imatinib treatment, validating the triomics results. These data show the utility of combining mass spectrometry-based "-omics" technologies and reveals that kinase inhibitors may not only downregulate phosphorylation of their targets but also induce metabolic events via increased phosphorylation of other cellular components.
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Affiliation(s)
- Susanne B. Breitkopf
- Division of Signal Transduction, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02115, United States
- Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115, United States
| | - Min Yuan
- Division of Signal Transduction, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02115, United States
| | - Katja P. Helenius
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Costas A. Lyssiotis
- Department of Molecular and Integrative Physiology and Division of Gastroenterology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - John M. Asara
- Division of Signal Transduction, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02115, United States
- Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115, United States
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19
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Quimbaya M, Raspé E, Denecker G, De Craene B, Roelandt R, Declercq W, Sagaert X, De Veylder L, Berx G. Deregulation of the replisome factor MCMBP prompts oncogenesis in colorectal carcinomas through chromosomal instability. Neoplasia 2015; 16:694-709. [PMID: 25246271 PMCID: PMC4235010 DOI: 10.1016/j.neo.2014.07.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Revised: 07/30/2014] [Accepted: 07/31/2014] [Indexed: 11/16/2022] Open
Abstract
Genetic instability has emerged as an important hallmark of human neoplasia. Although most types of cancers exhibit genetic instability to some extent, in colorectal cancers genetic instability is a distinctive characteristic. Recent studies have shown that deregulation of genes involved in sister chromatid cohesion can result in chromosomal instability in colorectal cancers. Here, we show that the replisome factor minichromosome maintenance complex–binding protein (MCMBP), which is directly involved in the dynamics of the minichromosome maintenance complex and contributes to maintaining sister chromatid cohesion, is transcriptionally misregulated in different types of carcinomas. Cellular studies revealed that both MCMBP knockdown and overexpression in different breast and colorectal cell lines is associated with the emergence of a subpopulation of cells with abnormal nuclear morphology that likely arise as a consequence of aberrant cohesion events. Association analysis integrating gene expression data with clinical information revealed that enhanced MCMBP transcript levels correlate with an increased probability of relapse risk in colorectal cancers and different types of carcinomas. Moreover, a detailed study of a cohort of colorectal tumors showed that the MCMBP protein accumulates to high levels in cancer cells, whereas in normal proliferating tissue its abundance is low, indicating that MCMBP could be exploited as a novel diagnostic marker for this type of carcinoma.
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Affiliation(s)
- Mauricio Quimbaya
- Unit of Molecular and Cellular Oncology, Inflammation Research Center, VIB, 9052 Ghent, Belgium; Department of Biomedical Molecular Biology, Ghent University, 9052 Ghent, Belgium; Department of Plant Systems Biology, VIB, 9052 Gent, Belgium; Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium; Pontificia Universidad Javeriana Cali, Department of Natural Sciences and Mathematics, Cali, Colombia
| | - Eric Raspé
- Unit of Molecular and Cellular Oncology, Inflammation Research Center, VIB, 9052 Ghent, Belgium; Department of Biomedical Molecular Biology, Ghent University, 9052 Ghent, Belgium
| | - Geertrui Denecker
- Unit of Molecular and Cellular Oncology, Inflammation Research Center, VIB, 9052 Ghent, Belgium; Department of Biomedical Molecular Biology, Ghent University, 9052 Ghent, Belgium
| | - Bram De Craene
- Unit of Molecular and Cellular Oncology, Inflammation Research Center, VIB, 9052 Ghent, Belgium; Department of Biomedical Molecular Biology, Ghent University, 9052 Ghent, Belgium
| | - Ria Roelandt
- Unit of Molecular Signaling and Cell Death, Department for Molecular Biomedical Research, VIB, 9052 Ghent, Belgium; Department of Biomedical Molecular Biology, Ghent University, 9052 Ghent, Belgium
| | - Wim Declercq
- Unit of Molecular Signaling and Cell Death, Department for Molecular Biomedical Research, VIB, 9052 Ghent, Belgium; Department of Biomedical Molecular Biology, Ghent University, 9052 Ghent, Belgium
| | - Xavier Sagaert
- Imaging and Pathology, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
| | - Lieven De Veylder
- Department of Plant Systems Biology, VIB, 9052 Gent, Belgium; Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium
| | - Geert Berx
- Unit of Molecular and Cellular Oncology, Inflammation Research Center, VIB, 9052 Ghent, Belgium; Department of Biomedical Molecular Biology, Ghent University, 9052 Ghent, Belgium.
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20
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Drissi R, Dubois ML, Douziech M, Boisvert FM. Quantitative Proteomics Reveals Dynamic Interactions of the Minichromosome Maintenance Complex (MCM) in the Cellular Response to Etoposide Induced DNA Damage. Mol Cell Proteomics 2015; 14:2002-13. [PMID: 25963833 PMCID: PMC4587322 DOI: 10.1074/mcp.m115.048991] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Indexed: 01/21/2023] Open
Abstract
The minichromosome maintenance complex (MCM) proteins are required for processive DNA replication and are a target of S-phase checkpoints. The eukaryotic MCM complex consists of six proteins (MCM2–7) that form a heterohexameric ring with DNA helicase activity, which is loaded on chromatin to form the pre-replication complex. Upon entry in S phase, the helicase is activated and opens the DNA duplex to recruit DNA polymerases at the replication fork. The MCM complex thus plays a crucial role during DNA replication, but recent work suggests that MCM proteins could also be involved in DNA repair. Here, we employed a combination of stable isotope labeling with amino acids in cell culture (SILAC)-based quantitative proteomics with immunoprecipitation of green fluorescent protein-tagged fusion proteins to identify proteins interacting with the MCM complex, and quantify changes in interactions in response to DNA damage. Interestingly, the MCM complex showed very dynamic changes in interaction with proteins such as Importin7, the histone chaperone ASF1, and the Chromodomain helicase DNA binding protein 3 (CHD3) following DNA damage. These changes in interactions were accompanied by an increase in phosphorylation and ubiquitination on specific sites on the MCM proteins and an increase in the co-localization of the MCM complex with γ-H2AX, confirming the recruitment of these proteins to sites of DNA damage. In summary, our data indicate that the MCM proteins is involved in chromatin remodeling in response to DNA damage.
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Affiliation(s)
- Romain Drissi
- From the ‡Department of Anatomy and Cell Biology, Université de Sherbrooke, 3201 Jean-Mignault, Sherbrooke, Québec, J1E 4K8, Canada
| | - Marie-Line Dubois
- From the ‡Department of Anatomy and Cell Biology, Université de Sherbrooke, 3201 Jean-Mignault, Sherbrooke, Québec, J1E 4K8, Canada
| | - Mélanie Douziech
- From the ‡Department of Anatomy and Cell Biology, Université de Sherbrooke, 3201 Jean-Mignault, Sherbrooke, Québec, J1E 4K8, Canada
| | - François-Michel Boisvert
- From the ‡Department of Anatomy and Cell Biology, Université de Sherbrooke, 3201 Jean-Mignault, Sherbrooke, Québec, J1E 4K8, Canada
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21
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Proteomics methods for discovering viral-host interactions. Methods 2015; 90:21-7. [PMID: 25959231 DOI: 10.1016/j.ymeth.2015.05.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 04/30/2015] [Accepted: 05/02/2015] [Indexed: 12/22/2022] Open
Abstract
The functions of many viral proteins involve direct interactions with specific host proteins. Therefore considerable insight into the functions of a viral protein and its mechanisms of action can come from applying proteomics approaches to viral proteins in order to identify their cellular binding partners. In this chapter we describe proteomics approaches that have proven to be the most useful in identifying host interactions of viral proteins in human cells. Caveats and potential alternatives for each step are also discussed.
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22
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Nangami G, Koumangoye R, Shawn Goodwin J, Sakwe AM, Marshall D, Higginbotham J, Ochieng J. Fetuin-A associates with histones intracellularly and shuttles them to exosomes to promote focal adhesion assembly resulting in rapid adhesion and spreading in breast carcinoma cells. Exp Cell Res 2014; 328:388-400. [PMID: 25194507 DOI: 10.1016/j.yexcr.2014.08.037] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2014] [Revised: 08/08/2014] [Accepted: 08/23/2014] [Indexed: 01/11/2023]
Abstract
The present analyses were undertaken to define the mechanisms by which fetuin-A modulates cellular adhesion. FLAG-tagged fetuin-A was expressed in breast carcinoma and HEK-293T cells. We demonstrated by confocal microscopy that fetuin-A co-localizes with histone H2A in the cell nucleus, forms stable complexes with histones such as H2A and H3 in solution, and shuttles histones to exosomes. The rate of cellular adhesion and spreading to either fibronectin or laminin coated wells was accelerated significantly in the presence of either endogenous fetuin-A or serum derived protein. More importantly, the formation of focal adhesion complexes on surfaces coated by laminin or fibronectin was accelerated in the presence of fetuin-A or histone coated exosomes. Cellular adhesion mediated by histone coated exosomes was abrogated by heparin and heparinase III. Heparinase III cleaves heparan sulfate from cell surface heparan sulfate proteoglycans. Lastly, the uptake of histone coated exosomes and subsequent cellular adhesion, was abrogated by heparin. Taken together, the data suggest a mechanism where fetuin-A, either endogenously synthesized or supplied extracellularly can extract histones from the nucleus or elsewhere in the cytosol/membrane and load them on cellular exosomes which then mediate adhesion by interacting with cell surface heparan sulfate proteoglycans via bound histones.
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Affiliation(s)
- Gladys Nangami
- Departments of Biochemistry and Cancer Biology, Meharry Medical College, 1005 D.B. Todd Boulevard, Nashville, TN 37208, USA
| | - Rainelli Koumangoye
- Division of Surgical Oncology and Endocrine Surgery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - J Shawn Goodwin
- Departments of Biochemistry and Cancer Biology, Meharry Medical College, 1005 D.B. Todd Boulevard, Nashville, TN 37208, USA
| | - Amos M Sakwe
- Departments of Biochemistry and Cancer Biology, Meharry Medical College, 1005 D.B. Todd Boulevard, Nashville, TN 37208, USA
| | - Dana Marshall
- Departments of Pathology, Anatomy and Cell Biology, Meharry Medical College, Nashville, TN 37208, USA
| | - James Higginbotham
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Josiah Ochieng
- Departments of Biochemistry and Cancer Biology, Meharry Medical College, 1005 D.B. Todd Boulevard, Nashville, TN 37208, USA.
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23
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Kusunoki S, Ishimi Y. Interaction of human minichromosome maintenance protein-binding protein with minichromosome maintenance 2-7. FEBS J 2014; 281:1057-67. [PMID: 24299456 DOI: 10.1111/febs.12668] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2013] [Accepted: 11/29/2013] [Indexed: 11/29/2022]
Abstract
It has been reported that minichromosome maintenance protein-binding protein (MCM-BP) functions in the formation of the pre-replication complex, unloading of minichromosome maintenance (MCM)2-7 from chromatin in late S phase, and formation of the cohesion complex by interacting with MCM3-7 proteins, suggesting that MCM-BP functions in several different reactions during the cell cycle. Here, we examined the interaction of human MCM-BP with MCM2-7 and structural maintenance of chromosome 3 in synchronized HeLa cells by immunoprecipitation. The results show that MCM-BP mainly interacts with MCM7 in the Triton-soluble fraction from S phase and G(2) phase cells, and it also interacts with structural maintenance of chromosome 3 in the fraction from G(2) phase cells. In vitro studies show that MCM-BP disassembles MCM2-7 bound to DNA with a fork-like structure by interacting with MCM3, MCM5, and MCM7. These results suggest that MCM-BP functions in disassembling MCM2-7 on chromatin during S phase and G2 phase by interacting with MCM3, MCM5, and MCM7.
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24
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Bosseboeuf A, Gautier A, Auvray P, Mazan S, Sourdaine P. Characterization of spermatogonial markers in the mature testis of the dogfish (Scyliorhinus canicula L.). Reproduction 2013; 147:125-39. [PMID: 24123129 DOI: 10.1530/rep-13-0316] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In dogfish, spermatogenesis progresses from a restricted germinative zone, which lines the dorsal testicular vessel. Single spermatogonia (A(s)), including the spermatogonial stem cells (SSCs), produce successively paired (A(p)), undifferentiated (A(u4) to A(u512)), and differentiated (A(d1) to A(d8)) spermatogonia and preleptotene (PL) spermatocytes through 13 mitoses. Dogfish spermatogonial subpopulations present classical morphological characteristics but cannot be distinguished on the basis of molecular markers. This characterization has been initiated in mammals despite the difficulty to separate each spermatogonial subpopulation. For instance, both glial cell-derived neurotrophic factor family receptor alpha 1 (GFRα1) and promyelocytic leukemia zinc finger protein (PLZF) are markers of undifferentiated spermatogonia, whereas receptor tyrosine kinase C-kit is a marker of differentiated spermatogonia. The aim of this study is to characterize spermatogonial markers and to differentiate several spermatogonial subpopulations. Dogfish cDNA sequences have been identified and validated by phylogenetic analyses for gfrα1, plzf, pou2, as well as for high-mobility group box proteins 2 and 3 (hmgb2 and 3) and for mini-chromosome maintenance protein 6 (mcm6). We have used the anatomical advantage of the polarized dogfish testis to analyze the expression of those markers by RT-PCR and in situ hybridization. gfrα1, pou2, and plzf have been detected in the testicular germinative zone, suggesting that spermatogonial markers are relatively well conserved among vertebrates but with a less restricted expression for plzf. Moreover, hmgb3 and mcm6 have been identified as new markers of differentiated spermatogonia. Finally, this first molecular characterization of spermatogonial subpopulations in a chondrichthyan model will be useful for further studies on the SSC niche evolution.
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25
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Abstract
The minichromosome maintenance (MCM) complex, which plays multiple important roles in DNA replication, is loaded onto chromatin following mitosis, remains on chromatin until the completion of DNA synthesis, and then is unloaded by a poorly defined mechanism that involves the MCM binding protein (MCM-BP). Here we show that MCM-BP directly interacts with the ubiquitin-specific protease USP7, that this interaction occurs predominantly on chromatin, and that MCM-BP can tether USP7 to MCM proteins. Detailed biochemical and structure analyses of the USP7-MCM-BP interaction showed that the (155)PSTS(158) MCM-BP sequence mediates critical interactions with the TRAF domain binding pocket of USP7. Analysis of the effects of USP7 knockout on DNA replication revealed that lack of USP7 results in slowed progression through late S phase without globally affecting the fork rate or origin usage. Lack of USP7 also resulted in increased levels of MCM proteins on chromatin, and investigation of the cause of this increase revealed a defect in the dissociation of MCM proteins from chromatin in mid- to late S phase. This role of USP7 mirrors the previously described role for MCM-BP in MCM complex unloading and suggests that USP7 works with MCM-BP to unload MCM complexes from chromatin at the end of S phase.
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26
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Hast BE, Goldfarb D, Mulvaney KM, Hast MA, Siesser PF, Yan F, Hayes DN, Major MB. Proteomic analysis of ubiquitin ligase KEAP1 reveals associated proteins that inhibit NRF2 ubiquitination. Cancer Res 2013; 73:2199-210. [PMID: 23382044 PMCID: PMC3618590 DOI: 10.1158/0008-5472.can-12-4400] [Citation(s) in RCA: 198] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Somatic mutations in the KEAP1 ubiquitin ligase or its substrate NRF2 (NFE2L2) commonly occur in human cancer, resulting in constitutive NRF2-mediated transcription of cytoprotective genes. However, many tumors display high NRF2 activity in the absence of mutation, supporting the hypothesis that alternative mechanisms of pathway activation exist. Previously, we and others discovered that via a competitive binding mechanism, the proteins WTX (AMER1), PALB2, and SQSTM1 bind KEAP1 to activate NRF2. Proteomic analysis of the KEAP1 protein interaction network revealed a significant enrichment of associated proteins containing an ETGE amino acid motif, which matches the KEAP1 interaction motif found in NRF2. Like WTX, PALB2, and SQSTM1, we found that the dipeptidyl peptidase 3 (DPP3) protein binds KEAP1 via an "ETGE" motif to displace NRF2, thus inhibiting NRF2 ubiquitination and driving NRF2-dependent transcription. Comparing the spectrum of KEAP1-interacting proteins with the genomic profile of 178 squamous cell lung carcinomas characterized by The Cancer Genome Atlas revealed amplification and mRNA overexpression of the DPP3 gene in tumors with high NRF2 activity but lacking NRF2 stabilizing mutations. We further show that tumor-derived mutations in KEAP1 are hypomorphic with respect to NRF2 inhibition and that DPP3 overexpression in the presence of these mutants further promotes NRF2 activation. Collectively, our findings further support the competition model of NRF2 activation and suggest that "ETGE"-containing proteins such as DPP3 contribute to NRF2 activity in cancer.
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MESH Headings
- Adaptor Proteins, Signal Transducing/physiology
- Animals
- Apoptosis
- Blotting, Western
- Carcinoma, Squamous Cell/genetics
- Carcinoma, Squamous Cell/metabolism
- Carcinoma, Squamous Cell/pathology
- Cell Proliferation
- Cells, Cultured
- Cohort Studies
- Cytoskeletal Proteins/physiology
- Dipeptidyl-Peptidases and Tripeptidyl-Peptidases/genetics
- Dipeptidyl-Peptidases and Tripeptidyl-Peptidases/metabolism
- Embryo, Mammalian/cytology
- Embryo, Mammalian/metabolism
- Fibroblasts/cytology
- Fibroblasts/metabolism
- Humans
- Immunoenzyme Techniques
- Kelch-Like ECH-Associated Protein 1
- Kidney/cytology
- Kidney/metabolism
- Luciferases/metabolism
- Lung/metabolism
- Lung/pathology
- Lung Neoplasms/genetics
- Lung Neoplasms/metabolism
- Lung Neoplasms/pathology
- Mice
- Mice, Knockout
- Mutagenesis, Site-Directed
- Mutation/genetics
- NF-E2-Related Factor 2/metabolism
- Proteomics
- RNA, Messenger/genetics
- Real-Time Polymerase Chain Reaction
- Reverse Transcriptase Polymerase Chain Reaction
- Ubiquitin/metabolism
- Ubiquitination
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Affiliation(s)
- Bridgid E. Hast
- Department of Cell Biology and Physiology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Box#7295, Chapel Hill, NC 27599, USA
| | - Dennis Goldfarb
- Department of Cell Biology and Physiology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Box#7295, Chapel Hill, NC 27599, USA
- Department of Computer Science, University of North Carolina at Chapel Hill, Box#3175, Chapel Hill, NC 27599, USA
| | - Kathleen M. Mulvaney
- Department of Cell Biology and Physiology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Box#7295, Chapel Hill, NC 27599, USA
| | - Michael A. Hast
- Department of Biochemistry, Duke University Medical Center, Box #3711, Durham NC, 27710, USA
| | - Priscila F. Siesser
- Department of Cell Biology and Physiology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Box#7295, Chapel Hill, NC 27599, USA
| | - Feng Yan
- Department of Cell Biology and Physiology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Box#7295, Chapel Hill, NC 27599, USA
| | - D. Neil Hayes
- Department of Internal Medicine and Otolaryngology, Division of Medical Oncology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Box#7295, Chapel Hill, NC 27599, USA
| | - Michael B. Major
- Department of Cell Biology and Physiology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Box#7295, Chapel Hill, NC 27599, USA
- Department of Computer Science, University of North Carolina at Chapel Hill, Box#3175, Chapel Hill, NC 27599, USA
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27
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Kim HS, Park SH, Günzl A, Cross GAM. MCM-BP is required for repression of life-cycle specific genes transcribed by RNA polymerase I in the mammalian infectious form of Trypanosoma brucei. PLoS One 2013; 8:e57001. [PMID: 23451133 PMCID: PMC3581582 DOI: 10.1371/journal.pone.0057001] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 01/16/2013] [Indexed: 12/22/2022] Open
Abstract
Trypanosoma brucei variant surface glycoprotein (VSG) expression is a classic example of allelic exclusion. While the genome of T. brucei contains >2,000 VSG genes and VSG pseudogenes, only one allele is expressed at the surface of each infectious trypanosome and the others are repressed. Along with recombinatorial VSG switching, allelic exclusion provides a major host evasion mechanism for trypanosomes, a phenomenon known as antigenic variation. To extend our understanding of how trypanosomes escape host immunity by differential expression of VSGs, we attempted to identify genes that contribute to VSG silencing, by performing a loss-of-silencing screen in T. brucei using a transposon-mediated random insertional mutagenesis. One identified gene, which we initially named LOS1, encodes a T. brucei MCM-Binding Protein (TbMCM-BP). Here we show that TbMCM-BP is essential for viability of infectious bloodstream-form (BF) trypanosome and is required for proper cell-cycle progression. Tandem affinity purification of TbMCM-BP followed by mass spectrometry identified four subunits (MCM4-MCM7) of the T. brucei MCM complex, a replicative helicase, and MCM8, a subunit that is uniquely co-purified with TbMCM-BP. TbMCM-BP is required not only for repression of subtelomeric VSGs but also for silencing of life-cycle specific, insect-stage genes, procyclin and procyclin-associated genes (PAGs), that are normally repressed in BF trypanosomes and are transcribed by RNA polymerase I. Our study uncovers a functional link between chromosome maintenance and RNA pol I-mediated gene silencing in T. brucei.
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Affiliation(s)
- Hee-Sook Kim
- Laboratory of Molecular Parasitology, The Rockefeller University, New York, New York, United States of America.
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28
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Santosa V, Martha S, Hirose N, Tanaka K. The fission yeast minichromosome maintenance (MCM)-binding protein (MCM-BP), Mcb1, regulates MCM function during prereplicative complex formation in DNA replication. J Biol Chem 2013; 288:6864-80. [PMID: 23322785 DOI: 10.1074/jbc.m112.432393] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The minichromosome maintenance (MCM) complex is a replicative helicase, which is essential for chromosome DNA replication. In recent years, the identification of a novel MCM-binding protein (MCM-BP) in most eukaryotes has led to numerous studies investigating its function and its relationship to the MCM complex. However, the mechanisms by which MCM-BP functions and associates with MCM complexes are not well understood; in addition, the functional role of MCM-BP remains controversial and may vary between model organisms. The present study aims to elucidate the nature and biological function of the MCM-BP ortholog, Mcb1, in fission yeast. The Mcb1 protein continuously interacts with MCM proteins during the cell cycle in vivo and can interact with any individual MCM subunit in vitro. To understand the detailed characteristics of mcb1(+), two temperature-sensitive mcb1 gene mutants (mcb1(ts)) were isolated. Extensive genetic analysis showed that the mcb1(ts) mutants were suppressed by a mcm5(+) multicopy plasmid and displayed synthetic defects with many S-phase-related gene mutants. Moreover, cyclin-dependent kinase modulation by Cig2 repression or Rum1 overproduction suppressed the mcb1(ts) mutants, suggesting the involvement of Mcb1 in pre-RC formation during DNA replication. These data are consistent with the observation that Mcm7 loading onto replication origins is reduced and S-phase progression is delayed in mcb1(ts) mutants. Furthermore, the mcb1(ts) mutation led to the redistribution of MCM subunits to the cytoplasm, and this redistribution was dependent on an active nuclear export system. These results strongly suggest that Mcb1 promotes efficient pre-RC formation during DNA replication by regulating the MCM complex.
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Affiliation(s)
- Venny Santosa
- Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan
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29
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Shen Z, Prasanth SG. Emerging players in the initiation of eukaryotic DNA replication. Cell Div 2012; 7:22. [PMID: 23075259 PMCID: PMC3520825 DOI: 10.1186/1747-1028-7-22] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 10/12/2012] [Indexed: 12/23/2022] Open
Abstract
Faithful duplication of the genome in eukaryotes requires ordered assembly of a multi-protein complex called the pre-replicative complex (pre-RC) prior to S phase; transition to the pre-initiation complex (pre-IC) at the beginning of DNA replication; coordinated progression of the replisome during S phase; and well-controlled regulation of replication licensing to prevent re-replication. These events are achieved by the formation of distinct protein complexes that form in a cell cycle-dependent manner. Several components of the pre-RC and pre-IC are highly conserved across all examined eukaryotic species. Many of these proteins, in addition to their bona fide roles in DNA replication are also required for other cell cycle events including heterochromatin organization, chromosome segregation and centrosome biology. As the complexity of the genome increases dramatically from yeast to human, additional proteins have been identified in higher eukaryotes that dictate replication initiation, progression and licensing. In this review, we discuss the newly discovered components and their roles in cell cycle progression.
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Affiliation(s)
- Zhen Shen
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601 S, Goodwin Avenue, Urbana, IL 61801, USA.
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30
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Interactions of the human MCM-BP protein with MCM complex components and Dbf4. PLoS One 2012; 7:e35931. [PMID: 22540012 PMCID: PMC3335088 DOI: 10.1371/journal.pone.0035931] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Accepted: 03/27/2012] [Indexed: 12/22/2022] Open
Abstract
MCM-BP was discovered as a protein that co-purified from human cells with MCM proteins 3 through 7; results which were recapitulated in frogs, yeast and plants. Evidence in all of these organisms supports an important role for MCM-BP in DNA replication, including contributions to MCM complex unloading. However the mechanisms by which MCM-BP functions and associates with MCM complexes are not well understood. Here we show that human MCM-BP is capable of interacting with individual MCM proteins 2 through 7 when co-expressed in insect cells and can greatly increase the recovery of some recombinant MCM proteins. Glycerol gradient sedimentation analysis indicated that MCM-BP interacts most strongly with MCM4 and MCM7. Similar gradient analyses of human cell lysates showed that only a small amount of MCM-BP overlapped with the migration of MCM complexes and that MCM complexes were disrupted by exogenous MCM-BP. In addition, large complexes containing MCM-BP and MCM proteins were detected at mid to late S phase, suggesting that the formation of specific MCM-BP complexes is cell cycle regulated. We also identified an interaction between MCM-BP and the Dbf4 regulatory component of the DDK kinase in both yeast 2-hybrid and insect cell co-expression assays, and this interaction was verified by co-immunoprecipitation of endogenous proteins from human cells. In vitro kinase assays showed that MCM-BP was not a substrate for DDK but could inhibit DDK phosphorylation of MCM4,6,7 within MCM4,6,7 or MCM2-7 complexes, with little effect on DDK phosphorylation of MCM2. Since DDK is known to activate DNA replication through phosphorylation of these MCM proteins, our results suggest that MCM-BP may affect DNA replication in part by regulating MCM phosphorylation by DDK.
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31
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Jagannathan M, Sakwe AM, Nguyen T, Frappier L. The MCM-associated protein MCM-BP is important for human nuclear morphology. J Cell Sci 2012; 125:133-43. [PMID: 22250201 DOI: 10.1242/jcs.089938] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Mini-chromosome maintenance complex-binding protein (MCM-BP) was discovered as a protein that is strongly associated with human MCM proteins, known to be crucial for DNA replication in providing DNA helicase activity. The Xenopus MCM-BP homologue appears to play a role in unloading MCM complexes from chromatin after DNA synthesis; however, the importance of MCM-BP and its functional contribution to human cells has been unclear. Here we show that depletion of MCM-BP by sustained expression of short hairpin RNA (shRNA) results in highly abnormal nuclear morphology and centrosome amplification. The abnormal nuclear morphology was not seen with depletion of other MCM proteins and was rescued with shRNA-resistant MCM-BP. MCM-BP depletion was also found to result in transient activation of the G2 checkpoint, slowed progression through G2 and increased replication protein A foci, indicative of replication stress. In addition, MCM-BP depletion led to increased cellular levels of MCM proteins throughout the cell cycle including soluble MCM pools. The results suggest that MCM-BP makes multiple contributions to human cells that are not limited to unloading of the MCM complex.
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Affiliation(s)
- Madhav Jagannathan
- Department of Molecular Genetics, University of Toronto, Toronto, Canada
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32
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Aves SJ, Liu Y, Richards TA. Evolutionary diversification of eukaryotic DNA replication machinery. Subcell Biochem 2012; 62:19-35. [PMID: 22918578 DOI: 10.1007/978-94-007-4572-8_2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
DNA replication research to date has focused on model organisms such as the vertebrate Xenopus laevis and the yeast species Saccharomyces cerevisiae and Schizosaccharomyces pombe. However, animals and fungi both belong to the Opisthokonta, one of about six eukaryotic phylogenetic 'supergroups', and therefore represent only a fraction of eukaryotic diversity. To explore evolutionary diversification of the eukaryotic DNA replication machinery a bioinformatic approach was used to investigate the presence or absence of yeast/animal replisome components in other eukaryotic taxa. A comparative genomic survey was undertaken of 59 DNA replication proteins in a diverse range of 36 eukaryotes from all six supergroups. Twenty-three proteins including Mcm2-7, Cdc45, RPA1, primase, some DNA polymerase subunits, RFC1-5, PCNA and Fen1 are present in all species examined. A further 20 proteins are present in all six eukaryotic supergroups, although not necessarily in every species: with the exception of RNase H2B and the fork protection complex component Timeless/Tof1, all of these are members of anciently derived paralogous families such as ORC, MCM, GINS or RPA. Together these form a set of 43 proteins that must have been present in the last common eukaryotic ancestor (LCEA). This minimal LCEA replisome is significantly more complex than the related replisome in Archaea, indicating evolutionary events including duplications of DNA replication genes in the LCEA lineage which parallel the early evolution of other complex eukaryotic cellular features.
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Affiliation(s)
- Stephen J Aves
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter, EX4 4QD, UK,
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33
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Kong BW, Lee JY, Bottje WG, Lassiter K, Lee J, Foster DN. Genome-wide differential gene expression in immortalized DF-1 chicken embryo fibroblast cell line. BMC Genomics 2011; 12:571. [PMID: 22111699 PMCID: PMC3258366 DOI: 10.1186/1471-2164-12-571] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Accepted: 11/23/2011] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND When compared to primary chicken embryo fibroblast (CEF) cells, the immortal DF-1 CEF line exhibits enhanced growth rates and susceptibility to oxidative stress. Although genes responsible for cell cycle regulation and antioxidant functions have been identified, the genome-wide transcription profile of immortal DF-1 CEF cells has not been previously reported. Global gene expression in primary CEF and DF-1 cells was performed using a 4X44K chicken oligo microarray. RESULTS A total of 3876 differentially expressed genes were identified with a 2 fold level cutoff that included 1706 up-regulated and 2170 down-regulated genes in DF-1 cells. Network and functional analyses using Ingenuity Pathways Analysis (IPA, Ingenuity® Systems, http://www.ingenuity.com) revealed that 902 of 3876 differentially expressed genes were classified into a number of functional groups including cellular growth and proliferation, cell cycle, cellular movement, cancer, genetic disorders, and cell death. Also, the top 5 gene networks with intermolecular connections were identified. Bioinformatic analyses suggested that DF-1 cells were characterized by enhanced molecular mechanisms for cell cycle progression and proliferation, suppressing cell death pathways, altered cellular morphogenesis, and accelerated capacity for molecule transport. Key molecules for these functions include E2F1, BRCA1, SRC, CASP3, and the peroxidases. CONCLUSIONS The global gene expression profiles provide insight into the cellular mechanisms that regulate the unique characteristics observed in immortal DF-1 CEF cells.
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Affiliation(s)
- Byung-Whi Kong
- Department of Poultry Science, Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, Arkansas 72701, USA.
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34
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Li JJ, Schnick J, Hayles J, MacNeill SA. Purification and functional inactivation of the fission yeast MCM(MCM-BP) complex. FEBS Lett 2011; 585:3850-5. [PMID: 22036784 DOI: 10.1016/j.febslet.2011.10.033] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Revised: 10/09/2011] [Accepted: 10/14/2011] [Indexed: 12/31/2022]
Abstract
The MCM (mini-chromosome maintenance) complex is the core of the eukaryotic replicative helicase and comprises six proteins, Mcm2-Mcm7. In humans, a variant form of the complex has Mcm2 replaced by the MCM-BP protein. Recent results suggest that a similar complex exists in fission yeast with an essential role in DNA replication and cell cycle progression. Here, we describe the purification and subunit composition of the fission yeast MCM(Mcb1) complex. Using newly generated temperature-sensitive alleles, we show that loss of MCM(Mcb1) function leads to accumulation of DNA damage, checkpoint activation and cell cycle arrest, and provide evidence for a role for MCM(Mcb1) in meiosis.
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Affiliation(s)
- Juan-juan Li
- Cancer Research UK London Research Institute, London, UK
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35
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Ding L, Forsburg SL. Schizosaccharomyces pombe minichromosome maintenance-binding protein (MCM-BP) antagonizes MCM helicase. J Biol Chem 2011; 286:32918-30. [PMID: 21813639 DOI: 10.1074/jbc.m111.282541] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The minichromosome maintenance (MCM) complex, a replicative helicase, is a heterohexamer essential for DNA duplication and genome stability. We identified Schizosaccharomyces pombe mcb1(+) (Mcm-binding protein 1), an apparent orthologue of the human MCM-binding protein that associates with a subset of MCM complex proteins. mcb1(+) is an essential gene. Deletion of mcb1(+) caused cell cycle arrest after several generations with a cdc phenotype and disrupted nuclear structure. Mcb1 is an abundant protein, constitutively present across the cell cycle. It is widely distributed in cytoplasm and nucleoplasm and bound to chromatin. Co-immunoprecipitation suggested that Mcb1 interacts robustly with Mcm3-7 but not Mcm2. Overproduction of Mcb1 disrupted the association of Mcm2 with other MCM proteins, resulting in inhibition of DNA replication, DNA damage, and activation of the checkpoint kinase Chk1. Thus, Mcb1 appears to antagonize the function of MCM helicase.
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Affiliation(s)
- Lin Ding
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, California 90089-2910, USA
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36
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Nishiyama A, Frappier L, Méchali M. MCM-BP regulates unloading of the MCM2-7 helicase in late S phase. Genes Dev 2010; 25:165-75. [PMID: 21196493 DOI: 10.1101/gad.614411] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Origins of DNA replication are licensed by recruiting MCM2-7 to assemble the prereplicative complex (pre-RC). How MCM2-7 is inactivated or removed from chromatin at the end of S phase is still unclear. Here, we show that MCM-BP can disassemble the MCM2-7 complex and might function as an unloader of MCM2-7 from chromatin. In Xenopus egg extracts, MCM-BP exists in a stable complex with MCM7, but is not associated with the MCM2-7 hexameric complex. MCM-BP accumulates in nuclei in late S phase, well after the loading of MCM2-7 onto chromatin. MCM-BP immunodepletion in Xenopus egg extracts inhibits replication-dependent MCM dissociation without affecting pre-RC formation and DNA replication. When excess MCM-BP is incubated with Xenopus egg extracts or immunopurified MCM2-7, it binds to MCM proteins and promotes disassembly of the MCM2-7 complex. Recombinant MCM-BP also releases MCM2-7 from isolated late-S-phase chromatin, but this activity is abolished when DNA replication is blocked. MCM-BP silencing in human cells also delays MCM dissociation in late S phase. We propose that MCM-BP plays a key role in the mechanism by which pre-RC is cleared from replicated DNA in vertebrate cells.
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37
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Nakaya R, Takaya J, Onuki T, Moritani M, Nozaki N, Ishimi Y. Identification of proteins that may directly interact with human RPA. ACTA ACUST UNITED AC 2010; 148:539-47. [DOI: 10.1093/jb/mvq085] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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38
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Xu X, Song Y, Li Y, Chang J, zhang H, An L. The tandem affinity purification method: An efficient system for protein complex purification and protein interaction identification. Protein Expr Purif 2010; 72:149-56. [DOI: 10.1016/j.pep.2010.04.009] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Revised: 04/08/2010] [Accepted: 04/09/2010] [Indexed: 10/19/2022]
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39
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Fazzio TG, Panning B. Condensin complexes regulate mitotic progression and interphase chromatin structure in embryonic stem cells. ACTA ACUST UNITED AC 2010; 188:491-503. [PMID: 20176923 PMCID: PMC2828918 DOI: 10.1083/jcb.200908026] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Loss of the condensin complex components Smc2 and -4 disrupts epigenetic modifications required for embryonic stem cell survival. In an RNA interference screen interrogating regulators of mouse embryonic stem (ES) cell chromatin structure, we previously identified 62 genes required for ES cell viability. Among these 62 genes were Smc2 and -4, which are core components of the two mammalian condensin complexes. In this study, we show that for Smc2 and -4, as well as an additional 49 of the 62 genes, knockdown (KD) in somatic cells had minimal effects on proliferation or viability. Upon KD, Smc2 and -4 exhibited two phenotypes that were unique to ES cells and unique among the ES cell–lethal targets: metaphase arrest and greatly enlarged interphase nuclei. Nuclear enlargement in condensin KD ES cells was caused by a defect in chromatin compaction rather than changes in DNA content. The altered compaction coincided with alterations in the abundance of several epigenetic modifications. These data reveal a unique role for condensin complexes in interphase chromatin compaction in ES cells.
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Affiliation(s)
- Thomas G Fazzio
- Biochemistry and Biophysics Department, University of California, San Francisco, San Francisco, CA 94158, USA.
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Takahashi N, Quimbaya M, Schubert V, Lammens T, Vandepoele K, Schubert I, Matsui M, Inzé D, Berx G, De Veylder L. The MCM-binding protein ETG1 aids sister chromatid cohesion required for postreplicative homologous recombination repair. PLoS Genet 2010; 6:e1000817. [PMID: 20090939 PMCID: PMC2806904 DOI: 10.1371/journal.pgen.1000817] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Accepted: 12/16/2009] [Indexed: 11/22/2022] Open
Abstract
The DNA replication process represents a source of DNA stress that causes potentially spontaneous genome damage. This effect might be strengthened by mutations in crucial replication factors, requiring the activation of DNA damage checkpoints to enable DNA repair before anaphase onset. Here, we demonstrate that depletion of the evolutionarily conserved minichromosome maintenance helicase-binding protein ETG1 of Arabidopsis thaliana resulted in a stringent late G2 cell cycle arrest. This arrest correlated with a partial loss of sister chromatid cohesion. The lack-of-cohesion phenotype was intensified in plants without functional CTF18, a replication fork factor needed for cohesion establishment. The synergistic effect of the etg1 and ctf18 mutants on sister chromatid cohesion strengthened the impact on plant growth of the replication stress caused by ETG1 deficiency because of inefficient DNA repair. We conclude that the ETG1 replication factor is required for efficient cohesion and that cohesion establishment is essential for proper development of plants suffering from endogenous DNA stress. Cohesion defects observed upon knockdown of its human counterpart suggest an equally important developmental role for the orthologous mammalian ETG1 protein. DNA replication is a highly complex process and the source of potential DNA damage. It is of utmost importance that the damaged DNA is repaired before cells proceed through mitosis, because the genome holds all the information required for correct development. DNA replication results in two identical sister chromatids. A trick applied by cells to overcome damaged DNA is homologous recombination, using the undamaged copy of the sister chromatid as a template to repair the damaged one. This process is aided by keeping the two sister chromatids in close proximity after the replication process by the deposition of a molecular glue, called cohesin. In the present work, we identified the Arabidopsis thaliana ETG1 protein as a novel evolutionarily conserved replication factor that is needed for maintaining the sister chromatids physically aligned. In plants without ETG1, DNA damage builds up due to inefficient DNA repair. As a consequence, cell division is impaired with a huge impact on plant growth, highlighting the importance of cohesin for the correct development of eukaryotic organisms. Cohesion phenotypes observed upon the depletion of the orthologous human ETG1 protein indicate equally prominent roles for this particular factor during mammalian development.
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Affiliation(s)
- Naoki Takahashi
- Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB), Gent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, Gent, Belgium
- Plant Functional Genomics Research Group, RIKEN Plant Science Center, Yokohama, Kanagawa, Japan
| | - Mauricio Quimbaya
- Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB), Gent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, Gent, Belgium
- Department for Molecular Biomedical Research, Molecular and Cellular Oncology Unit, Flanders Institute for Biotechnology (VIB), Gent, Belgium
- Department of Biomedical Molecular Biology, Ghent University, Gent, Belgium
| | - Veit Schubert
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Germany
| | - Tim Lammens
- Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB), Gent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, Gent, Belgium
| | - Klaas Vandepoele
- Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB), Gent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, Gent, Belgium
| | - Ingo Schubert
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Germany
| | - Minami Matsui
- Plant Functional Genomics Research Group, RIKEN Plant Science Center, Yokohama, Kanagawa, Japan
| | - Dirk Inzé
- Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB), Gent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, Gent, Belgium
| | - Geert Berx
- Department for Molecular Biomedical Research, Molecular and Cellular Oncology Unit, Flanders Institute for Biotechnology (VIB), Gent, Belgium
- Department of Biomedical Molecular Biology, Ghent University, Gent, Belgium
| | - Lieven De Veylder
- Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB), Gent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, Gent, Belgium
- * E-mail:
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Abstract
The eukaryotic MCM2-7 complex is recruited onto origins of replication during the G1 phase of the cell cycle and acts as the main helicase at the replication fork during the S phase. Over the last few years a number of structural reports on MCM proteins using both electron microscopy and protein crystallography have been published. The crystal structures of two (almost) full-length archaeal homologs provide the first atomic pictures of a MCM helicase. However one of the structures is at low resolution and the other is of an inactive MCM. Moreover, both proteins are monomeric in the crystal, whereas the activity of the complex is critically dependent on oligomerization. Lower resolution structures derived from electron microscopy studies are therefore crucial to complement the crystallographic analysis and to assemble the multimeric complex that is active in the cell. A critical analysis of all the structural results elucidates the potential conformational changes and dynamic behavior of MCM helicase to provide a first insight into the gamut of molecular configurations adopted during the processes of DNA melting and unwinding.
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Stable complex formation between HIV Rev and the nucleosome assembly protein, NAP1, affects Rev function. Virology 2009; 388:103-11. [PMID: 19339032 DOI: 10.1016/j.virol.2009.03.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Revised: 01/10/2009] [Accepted: 03/06/2009] [Indexed: 11/23/2022]
Abstract
The Rev protein of HIV-1 is essential for HIV-1 proliferation due to its role in exporting viral RNA from the nucleus. We used a modified version of tandem affinity purification (TAP) tagging to identify proteins interacting with HIV-1 Rev in human cells and discovered a prominent interaction between Rev and nucleosome assembly protein 1 (Nap1). This interaction was also observed by specific retention of Nap1 from human cell lysates on a Rev affinity column. Nap1 was found to bind Rev through the Rev arginine-rich domain and altered the oligomerization state of Rev in vitro. Overexpression of Nap1 stimulated the ability of Rev to export RNA, reduced the nucleolar localization of Rev, and affected Rev nuclear import rates. The results suggest that Nap-1 may influence Rev function by increasing the availability of Rev.
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Subunit organization of Mcm2-7 and the unequal role of active sites in ATP hydrolysis and viability. Mol Cell Biol 2008; 28:5865-73. [PMID: 18662997 DOI: 10.1128/mcb.00161-08] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The Mcm2-7 (minichromosome maintenance) complex is a toroidal AAA(+) ATPase and the putative eukaryotic replicative helicase. Unlike a typical homohexameric helicase, Mcm2-7 contains six distinct, essential, and evolutionarily conserved subunits. Precedence to other AAA(+) proteins suggests that Mcm ATPase active sites are formed combinatorially, with Walker A and B motifs contributed by one subunit and a catalytically essential arginine (arginine finger) contributed by the adjacent subunit. To test this prediction, we used copurification experiments to identify five distinct and stable Mcm dimer combinations as potential active sites; these subunit associations predict the architecture of the Mcm2-7 complex. Through the use of mutant subunits, we establish that at least three sites are active for ATP hydrolysis and have a canonical AAA(+) configuration. In isolation, these five active-site dimers have a wide range of ATPase activities. Using Walker B and arginine finger mutations in defined Mcm subunits, we demonstrate that these sites similarly make differential contributions toward viability and ATP hydrolysis within the intact hexamer. Our conclusions predict a structural discontinuity between Mcm2 and Mcm5 and demonstrate that in contrast to other hexameric helicases, the six Mcm2-7 active sites are functionally distinct.
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The DNA replication checkpoint aids survival of plants deficient in the novel replisome factor ETG1. EMBO J 2008; 27:1840-51. [PMID: 18528439 DOI: 10.1038/emboj.2008.107] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2008] [Accepted: 05/07/2008] [Indexed: 12/23/2022] Open
Abstract
Complete and accurate chromosomal DNA replication is essential for the maintenance of the genetic integrity of all organisms. Errors in replication are buffered by the activation of DNA stress checkpoints; however, in plants, the relative importance of a coordinated induction of DNA repair and cell cycle-arresting genes in the survival of replication mutants is unknown. In a systematic screen for Arabidopsis thaliana E2F target genes, the E2F TARGET GENE 1 (ETG1) was identified as a novel evolutionarily conserved replisome factor. ETG1 was associated with the minichromosome maintenance complex and was crucial for efficient DNA replication. Plants lacking the ETG1 gene had serrated leaves due to cell cycle inhibition triggered by the DNA replication checkpoints, as shown by the transcriptional induction of DNA stress checkpoint genes. The importance of checkpoint activation was highlighted by double mutant analysis: whereas etg1 mutant plants developed relatively normally, a synthetically lethal interaction was observed between etg1 and the checkpoint mutants wee1 and atr, demonstrating that activation of a G2 cell cycle checkpoint accounts for survival of ETG1-deficient plants.
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Abstract
Eukaryotic DNA replication is regulated to ensure all chromosomes replicate once and only once per cell cycle. Replication begins at many origins scattered along each chromosome. Except for budding yeast, origins are not defined DNA sequences and probably are inherited by epigenetic mechanisms. Initiation at origins occurs throughout the S phase according to a temporal program that is important in regulating gene expression during development. Most replication proteins are conserved in evolution in eukaryotes and archaea, but not in bacteria. However, the mechanism of initiation is conserved and consists of origin recognition, assembly of prereplication (pre-RC) initiative complexes, helicase activation, and replisome loading. Cell cycle regulation by protein phosphorylation ensures that pre-RC assembly can only occur in G1 phase, whereas helicase activation and loading can only occur in S phase. Checkpoint regulation maintains high fidelity by stabilizing replication forks and preventing cell cycle progression during replication stress or damage.
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Affiliation(s)
- R A Sclafani
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO 80045, USA.
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Komamura-Kohno Y, Tanaka R, Omori A, Kohno T, Ishimi Y. Biochemical characterization of fragmented human MCM2. FEBS J 2008; 275:727-38. [PMID: 18190532 DOI: 10.1111/j.1742-4658.2007.06239.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The molecular dissection of human MCM2, a constituent of MCM2-7 licensing factor complex, was performed to identify the region responsible for its biochemical activities. Partial digestion with trypsin dissected the MCM2 protein into a central region (148-676) containing ATPase motifs and a C-terminal region (677-895). These two fragments, along with three other fragments (148-441, 442-676 and 442-895), were produced using the wheat germ cell-free system and were examined for their ability to inhibit MCM4/6/7 helicase activity. Two fragments (442-895 and 677-895) containing the C-terminus were partly inhibitory to the activity. Further dissection revealed that one fragment (713-895) has strong inhibitory activity. The inhibitory activity of the smaller fragments derived from the C-terminal region correlated with their ability to inhibit SV40 T antigen helicase activity and also with their ability to bind to ssDNA, which has been shown by gel mobility shift analysis. These results strongly suggest that the MCM2 fragments derived from the C-terminal region inhibit DNA helicase activity through their ability to bind to ssDNA. In contrast, two fragments (148-441 and 442-676) from the central region were mainly responsible for the interaction between MCM2 and MCM4, and this was revealed by a pulldown analysis using MCM4 protein beads. Finally, only complete MCM2, not the smaller fragments, could disassemble the MCM4/6/7 hexamer into the MCM2/4/6/7 tetramer.
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Affiliation(s)
- Yuki Komamura-Kohno
- Mitsubishi Kagaku Institute of Life Sciences (MITILS), Machida, Tokyo, Japan
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Maeng YH, Kang HW, Huh JS. The Expression and Clinical Significance of the Minichromosome Maintenance (MCM) 7 Proliferation Markers in Urothelial Carcinomas of the Bladder. Korean J Urol 2008. [DOI: 10.4111/kju.2008.49.1.12] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Young-Hee Maeng
- Department of Patholgy, School of Medicine, Cheju University, Jeju, Korea
| | - Hyun Wook Kang
- Department of Forensic Medicine, School of Medicine, Cheju University, Jeju, Korea
| | - Jung-Sik Huh
- Department of Urology, School of Medicine, Cheju University, Jeju, Korea
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Pruitt SC, Bailey KJ, Freeland A. Reduced Mcm2 expression results in severe stem/progenitor cell deficiency and cancer. Stem Cells 2007; 25:3121-32. [PMID: 17717065 DOI: 10.1634/stemcells.2007-0483] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Mcm2 is a component of the DNA replication licensing complex that marks DNA replication origins during G1 of the cell cycle for use in the subsequent S-phase. It is expressed in stem/progenitor cells in a variety of regenerative tissues in mammals. Here, we have used the Mcm2 gene to develop a transgenic mouse in which somatic stem/progenitor cells can be genetically modified in the adult. In these mice, a tamoxifen-inducible form of Cre recombinase is integrated 3' to the Mcm2 coding sequence and expressed via an internal ribosome entry site (IRES). Heterozygous Mcm2(IRES-CreERT2/wild-type (wt)) mice are phenotypically indistinguishable from wild-type at least through 1 year of age. In bigenic Mcm2(IRES-CreERT2/wt); Z/EG reporter mice, tamoxifen-dependent enhanced green fluorescence protein expression is inducible in a wide variety of somatic stem cells and their progeny. However, in Mcm2(IRES-CreERT2/IRES-CreERT2) homozygous embryos or mouse embryonic fibroblasts, Mcm2 is reduced to approximately one-third of wild-type levels. Despite the fact that these mice develop normally and are asymptomatic as young adults, life span is greatly reduced, with most surviving to only approximately 10-12 weeks of age. They demonstrate severe deficiencies in the proliferative cell compartments of a variety of tissues, including the subventricular zone of the brain, muscle, and intestinal crypts. However, the immediate cause of death in most of these animals is cancer, where the majority develop lymphomas. These studies directly demonstrate that deficiencies in the function of the core DNA replication machinery that are compatible with development and survival nonetheless result in a chronic phenotype leading to stem cell deficiency in multiple tissues and cancer. Disclosure of potential conflicts of interest is found at the end of this article.
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Affiliation(s)
- Steven C Pruitt
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, New York 14263, USA.
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