1
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Rankin BD, Rankin S. The MCM2-7 Complex: Roles beyond DNA Unwinding. BIOLOGY 2024; 13:258. [PMID: 38666870 PMCID: PMC11048021 DOI: 10.3390/biology13040258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 04/07/2024] [Accepted: 04/11/2024] [Indexed: 04/28/2024]
Abstract
The MCM2-7 complex is a hexameric protein complex that serves as a DNA helicase. It unwinds the DNA double helix during DNA replication, thereby providing the single-stranded replication template. In recent years, it has become clear that the MCM2-7 complex has additional functions that extend well beyond its role in DNA replication. Through physical and functional interactions with different pathways, it impacts other nuclear events and activities, including folding of the genome, histone inheritance, chromosome segregation, DNA damage sensing and repair, and gene transcription. Collectively, the diverse roles of the MCM2-7 complex suggest it plays a critical role in maintaining genome integrity by integrating the regulation of DNA replication with other pathways in the nucleus.
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Affiliation(s)
- Brooke D. Rankin
- Cell Cycle and Cancer Biology Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA;
- Cell Biology Department, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Susannah Rankin
- Cell Cycle and Cancer Biology Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA;
- Cell Biology Department, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
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2
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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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3
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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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4
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Aze A, Hutchins JRA, Maiorano D. Studying Translesion DNA Synthesis Using Xenopus In Vitro Systems. Methods Mol Biol 2024; 2740:21-36. [PMID: 38393467 DOI: 10.1007/978-1-0716-3557-5_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2024]
Abstract
Cell-free extracts derived from Xenopus eggs have been widely used to decipher molecular pathways involved in several cellular processes including DNA synthesis, the DNA damage response, and genome integrity maintenance. We set out assays using Xenopus cell-free extracts to study translesion DNA synthesis (TLS), a branch of the DNA damage tolerance pathway that allows replication of damaged DNA. Using this system, we were able to recapitulate TLS activities that occur naturally in vivo during early embryogenesis. This chapter describes protocols to detect chromatin-bound TLS factors by western blotting and immunofluorescence microscopy upon induction of DNA damage by UV irradiation, monitor TLS-dependent mutagenesis, and perform proteomic screening.
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Affiliation(s)
- Antoine Aze
- Genome Surveillance and Stability Laboratory, Institute of Human Genetics, UMR9002, CNRS-University of Montpellier, Montpellier, France
| | - James R A Hutchins
- Genome Surveillance and Stability Laboratory, Institute of Human Genetics, UMR9002, CNRS-University of Montpellier, Montpellier, France
| | - Domenico Maiorano
- Genome Surveillance and Stability Laboratory, Institute of Human Genetics, UMR9002, CNRS-University of Montpellier, Montpellier, France.
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5
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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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6
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Chi L, Wang H, Yu F, Gao C, Dai H, Si X, Liu L, Wang Z, Zheng J, Ke Y, Liu H, Zhang Q. Recent Progress of Ubiquitin-Specific-Processing Protease 7 Inhibitors. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2023. [DOI: 10.1134/s1068162023020073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
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7
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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: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2022] [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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8
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Sabatier P, Beusch CM, Gencheva R, Cheng Q, Zubarev R, Arnér ESJ. Comprehensive chemical proteomics analyses reveal that the new TRi-1 and TRi-2 compounds are more specific thioredoxin reductase 1 inhibitors than auranofin. Redox Biol 2021; 48:102184. [PMID: 34788728 PMCID: PMC8591550 DOI: 10.1016/j.redox.2021.102184] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 11/06/2021] [Accepted: 11/09/2021] [Indexed: 12/16/2022] Open
Abstract
Anticancer drugs that target cellular antioxidant systems have recently attracted much attention. Auranofin (AF) is currently evaluated in several clinical trials as an anticancer agent that targets the cytosolic and mitochondrial forms of the selenoprotein thioredoxin reductase, TXNRD1 and TXNRD2. Recently, two novel TXNRD1 inhibitors (TRi-1 and TRi-2) have been developed that showed anticancer efficacy comparable to AF, but with lower mitochondrial toxicity. However, the cellular action mechanisms of these drugs have not yet been thoroughly studied. Here we used several proteomics approaches to determine the effects of AF, TRi-1 and TRi-2 when used at IC50 concentrations with the mouse B16 melanoma and LLC lung adenocarcinoma cells, as these are often used for preclinical mouse models in evaluation of anticancer drugs. The results demonstrate that TRi-1 and TRi-2 are more specific TXNRD1 inhibitors than AF and reveal additional AF-specific effects on the cellular proteome. Interestingly, AF triggered stronger Nrf2-driven antioxidant responses than the other two compounds. Furthermore, AF affected several additional proteins, including GSK3A, GSK3B, MCMBP and EEFSEC, implicating additional effects on glycogen metabolism, cellular differentiation, inflammatory pathways, DNA replication and selenoprotein synthesis processes. Our proteomics data provide a resource for researchers interested in the multidimensional analysis of proteome changes associated with oxidative stress in general, and the effects of TXNRD1 inhibitors and AF protein targets in particular.
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Affiliation(s)
- Pierre Sabatier
- Chemistry I, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, 17177, Sweden
| | - Christian M Beusch
- Chemistry I, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, 17177, Sweden
| | - Radosveta Gencheva
- Division of Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, 17177, Sweden
| | - Qing Cheng
- Division of Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, 17177, Sweden
| | - Roman Zubarev
- Chemistry I, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, 17177, Sweden; Department of Pharmacological & Technological Chemistry, I.M. Sechenov First Moscow State Medical University, Moscow, 119146, Russia; The National Medical Research Center for Endocrinology, 115478, Moscow, Russia.
| | - Elias S J Arnér
- Division of Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, 17177, Sweden; Department of Selenoprotein Research, National Institute of Oncology, 1122, Budapest, Hungary.
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9
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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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10
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Fan Y, Köberlin MS, Ratnayeke N, Liu C, Deshpande M, Gerhardt J, Meyer T. LRR1-mediated replisome disassembly promotes DNA replication by recycling replisome components. J Cell Biol 2021; 220:212186. [PMID: 34037657 PMCID: PMC8160578 DOI: 10.1083/jcb.202009147] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 03/30/2021] [Accepted: 05/04/2021] [Indexed: 11/22/2022] Open
Abstract
After two converging DNA replication forks meet, active replisomes are disassembled and unloaded from chromatin. A key process in replisome disassembly is the unloading of CMG helicases (CDC45–MCM–GINS), which is initiated in Caenorhabditis elegans and Xenopus laevis by the E3 ubiquitin ligase CRL2LRR1. Here, we show that human cells lacking LRR1 fail to unload CMG helicases and accumulate increasing amounts of chromatin-bound replisome components as cells progress through S phase. Markedly, we demonstrate that the failure to disassemble replisomes reduces the rate of DNA replication increasingly throughout S phase by sequestering rate-limiting replisome components on chromatin and blocking their recycling. Continued binding of CMG helicases to chromatin during G2 phase blocks mitosis by activating an ATR-mediated G2/M checkpoint. Finally, we provide evidence that LRR1 is an essential gene for human cell division, suggesting that CRL2LRR1 enzyme activity is required for the proliferation of cancer cells and is thus a potential target for cancer therapy.
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Affiliation(s)
- Yilin Fan
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA.,Department of Cell and Developmental Biology, Weill Cornell Medicine, New York, NY
| | - Marielle S Köberlin
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA
| | - Nalin Ratnayeke
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA.,Department of Cell and Developmental Biology, Weill Cornell Medicine, New York, NY
| | - Chad Liu
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA
| | - Madhura Deshpande
- Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medicine, New York, NY
| | - Jeannine Gerhardt
- Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medicine, New York, NY.,Department of Obstetrics and Gynecology, Weill Cornell Medicine, New York, NY
| | - Tobias Meyer
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA.,Department of Cell and Developmental Biology, Weill Cornell Medicine, New York, NY
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11
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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: 54] [Impact Index Per Article: 13.5] [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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12
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Valles GJ, Bezsonova I, Woodgate R, Ashton NW. USP7 Is a Master Regulator of Genome Stability. Front Cell Dev Biol 2020; 8:717. [PMID: 32850836 PMCID: PMC7419626 DOI: 10.3389/fcell.2020.00717] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 07/13/2020] [Indexed: 12/25/2022] Open
Abstract
Genetic alterations, including DNA mutations and chromosomal abnormalities, are primary drivers of tumor formation and cancer progression. These alterations can endow cells with a selective growth advantage, enabling cancers to evade cell death, proliferation limits, and immune checkpoints, to metastasize throughout the body. Genetic alterations occur due to failures of the genome stability pathways. In many cancers, the rate of alteration is further accelerated by the deregulation of these processes. The deubiquitinating enzyme ubiquitin specific protease 7 (USP7) has recently emerged as a key regulator of ubiquitination in the genome stability pathways. USP7 is also deregulated in many cancer types, where deviances in USP7 protein levels are correlated with cancer progression. In this work, we review the increasingly evident role of USP7 in maintaining genome stability, the links between USP7 deregulation and cancer progression, as well as the rationale of targeting USP7 in cancer therapy.
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Affiliation(s)
- Gabrielle J Valles
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, CT, United States
| | - Irina Bezsonova
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, CT, United States
| | - Roger Woodgate
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
| | - Nicholas W Ashton
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
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13
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Damasceno JD, Reis-Cunha J, Crouch K, Beraldi D, Lapsley C, Tosi LRO, Bartholomeu D, McCulloch R. Conditional knockout of RAD51-related genes in Leishmania major reveals a critical role for homologous recombination during genome replication. PLoS Genet 2020; 16:e1008828. [PMID: 32609721 PMCID: PMC7360064 DOI: 10.1371/journal.pgen.1008828] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 07/14/2020] [Accepted: 05/05/2020] [Indexed: 12/12/2022] Open
Abstract
Homologous recombination (HR) has an intimate relationship with genome replication, both during repair of DNA lesions that might prevent DNA synthesis and in tackling stalls to the replication fork. Recent studies led us to ask if HR might have a more central role in replicating the genome of Leishmania, a eukaryotic parasite. Conflicting evidence has emerged regarding whether or not HR genes are essential, and genome-wide mapping has provided evidence for an unorthodox organisation of DNA replication initiation sites, termed origins. To answer this question, we have employed a combined CRISPR/Cas9 and DiCre approach to rapidly generate and assess the effect of conditional ablation of RAD51 and three RAD51-related proteins in Leishmania major. Using this approach, we demonstrate that loss of any of these HR factors is not immediately lethal but in each case growth slows with time and leads to DNA damage and accumulation of cells with aberrant DNA content. Despite these similarities, we show that only loss of RAD51 or RAD51-3 impairs DNA synthesis and causes elevated levels of genome-wide mutation. Furthermore, we show that these two HR factors act in distinct ways, since ablation of RAD51, but not RAD51-3, has a profound effect on DNA replication, causing loss of initiation at the major origins and increased DNA synthesis at subtelomeres. Our work clarifies questions regarding the importance of HR to survival of Leishmania and reveals an unanticipated, central role for RAD51 in the programme of genome replication in a microbial eukaryote.
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Affiliation(s)
- Jeziel D. Damasceno
- The Wellcome Centre for Integrative Parasitology, University of Glasgow, Institute of Infection, Immunity and Inflammation, Sir Graeme Davies Building, 120 University Place, Glasgow, United Kingdom
- * E-mail: (JDD); (RM)
| | - João Reis-Cunha
- Laboratório de Imunologia e Genômica de Parasitos, Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brasil
| | - Kathryn Crouch
- The Wellcome Centre for Integrative Parasitology, University of Glasgow, Institute of Infection, Immunity and Inflammation, Sir Graeme Davies Building, 120 University Place, Glasgow, United Kingdom
| | - Dario Beraldi
- The Wellcome Centre for Integrative Parasitology, University of Glasgow, Institute of Infection, Immunity and Inflammation, Sir Graeme Davies Building, 120 University Place, Glasgow, United Kingdom
| | - Craig Lapsley
- The Wellcome Centre for Integrative Parasitology, University of Glasgow, Institute of Infection, Immunity and Inflammation, Sir Graeme Davies Building, 120 University Place, Glasgow, United Kingdom
| | - Luiz R. O. Tosi
- Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo; Ribeirão Preto, SP, Brazil
| | - Daniella Bartholomeu
- Laboratório de Imunologia e Genômica de Parasitos, Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brasil
| | - Richard McCulloch
- The Wellcome Centre for Integrative Parasitology, University of Glasgow, Institute of Infection, Immunity and Inflammation, Sir Graeme Davies Building, 120 University Place, Glasgow, United Kingdom
- * E-mail: (JDD); (RM)
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Interaction of Deubiquitinase 2A-DUB/MYSM1 with DNA Repair and Replication Factors. Int J Mol Sci 2020; 21:ijms21113762. [PMID: 32466590 PMCID: PMC7312997 DOI: 10.3390/ijms21113762] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Revised: 05/07/2020] [Accepted: 05/19/2020] [Indexed: 01/09/2023] Open
Abstract
The deubiquitination of histone H2A on lysine 119 by 2A-DUB/MYSM1, BAP1, USP16, and other enzymes is required for key cellular processes, including transcriptional activation, apoptosis, and cell cycle control, during normal hematopoiesis and tissue development, and in tumor cells. Based on our finding that MYSM1 colocalizes with γH2AX foci in human peripheral blood mononuclear cells, leukemia cells, and melanoma cells upon induction of DNA double-strand breaks with topoisomerase inhibitor etoposide, we applied a mass spectrometry-based proteomics approach to identify novel 2A-DUB/MYSM1 interaction partners in DNA-damage responses. Differential display of MYSM1 binding proteins significantly enriched after exposure of 293T cells to etoposide revealed an interacting network of proteins involved in DNA damage and replication, including factors associated with poor melanoma outcome. In the context of increased DNA-damage in a variety of cell types in Mysm1-deficient mice, in bone marrow cells upon aging and in UV-exposed Mysm1-deficient skin, our current mass spectrometry data provide additional evidence for an interaction between MYSM1 and key DNA replication and repair factors, and indicate a potential function of 2A-DUB/MYSM1 in DNA repair processes.
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15
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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 PMCID: PMC6817399 DOI: 10.1002/1873-3468.13619] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [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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16
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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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17
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Coulombe P, Nassar J, Peiffer I, Stanojcic S, Sterkers Y, Delamarre A, Bocquet S, Méchali M. The ORC ubiquitin ligase OBI1 promotes DNA replication origin firing. Nat Commun 2019; 10:2426. [PMID: 31160578 PMCID: PMC6547688 DOI: 10.1038/s41467-019-10321-x] [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: 06/11/2018] [Accepted: 04/23/2019] [Indexed: 12/21/2022] Open
Abstract
DNA replication initiation is a two-step process. During the G1-phase of the cell cycle, the ORC complex, CDC6, CDT1, and MCM2-7 assemble at replication origins, forming pre-replicative complexes (pre-RCs). In S-phase, kinase activities allow fork establishment through (CDC45/MCM2-7/GINS) CMG-complex formation. However, only a subset of all potential origins becomes activated, through a poorly understood selection mechanism. Here we analyse the pre-RC proteomic interactome in human cells and find C13ORF7/RNF219 (hereafter called OBI1, for ORC-ubiquitin-ligase-1) associated with the ORC complex. OBI1 silencing result in defective origin firing, as shown by reduced CMG formation, without affecting pre-RC establishment. OBI1 catalyses the multi-mono-ubiquitylation of a subset of chromatin-bound ORC3 and ORC5 during S-phase. Importantly, expression of non-ubiquitylable ORC3/5 mutants impairs origin firing, demonstrating their relevance as OBI1 substrates for origin firing. Our results identify a ubiquitin signalling pathway involved in origin activation and provide a candidate protein for selecting the origins to be fired.
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Affiliation(s)
- Philippe Coulombe
- Institute of Human Genetics, UMR 9002, CNRS-Université de Montpellier, 141 rue de la Cardonille, 34396, Montpellier, France.
| | - Joelle Nassar
- Institute of Human Genetics, UMR 9002, CNRS-Université de Montpellier, 141 rue de la Cardonille, 34396, Montpellier, France
| | - Isabelle Peiffer
- Institute of Human Genetics, UMR 9002, CNRS-Université de Montpellier, 141 rue de la Cardonille, 34396, Montpellier, France
| | - Slavica Stanojcic
- CNRS 5290 - IRD 224 - University of Montpellier (UMR "MiVEGEC"), 34090, Montpellier, France
| | - Yvon Sterkers
- CNRS 5290 - IRD 224 - University of Montpellier (UMR "MiVEGEC"), 34090, Montpellier, France.,University Hospital Centre (CHU), Department of Parasitology-Mycology, 34090, Montpellier, France
| | - Axel Delamarre
- Institute of Human Genetics, UMR 9002, CNRS-Université de Montpellier, 141 rue de la Cardonille, 34396, Montpellier, France
| | - Stéphane Bocquet
- Institute of Human Genetics, UMR 9002, CNRS-Université de Montpellier, 141 rue de la Cardonille, 34396, Montpellier, France
| | - Marcel Méchali
- Institute of Human Genetics, UMR 9002, CNRS-Université de Montpellier, 141 rue de la Cardonille, 34396, Montpellier, France.
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18
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Origin Firing Regulations to Control Genome Replication Timing. Genes (Basel) 2019; 10:genes10030199. [PMID: 30845782 PMCID: PMC6470937 DOI: 10.3390/genes10030199] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 02/25/2019] [Accepted: 02/28/2019] [Indexed: 12/19/2022] Open
Abstract
Complete genome duplication is essential for genetic homeostasis over successive cell generations. Higher eukaryotes possess a complex genome replication program that involves replicating the genome in units of individual chromatin domains with a reproducible order or timing. Two types of replication origin firing regulations ensure complete and well-timed domain-wise genome replication: (1) the timing of origin firing within a domain must be determined and (2) enough origins must fire with appropriate positioning in a short time window to avoid inter-origin gaps too large to be fully copied. Fundamental principles of eukaryotic origin firing are known. We here discuss advances in understanding the regulation of origin firing to control firing time. Work with yeasts suggests that eukaryotes utilise distinct molecular pathways to determine firing time of distinct sets of origins, depending on the specific requirements of the genomic regions to be replicated. Although the exact nature of the timing control processes varies between eukaryotes, conserved aspects exist: (1) the first step of origin firing, pre-initiation complex (pre-IC formation), is the regulated step, (2) many regulation pathways control the firing kinase Dbf4-dependent kinase, (3) Rif1 is a conserved mediator of late origin firing and (4) competition between origins for limiting firing factors contributes to firing timing. Characterization of the molecular timing control pathways will enable us to manipulate them to address the biological role of replication timing, for example, in cell differentiation and genome instability.
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Abstract
Recently published structural and functional analyses of the CMG complex have provided insight into the mechanism of its DNA helicase function and into the distinct roles of its central six component proteins MCM2-MCM7 (MCM2-7). To activate CMG helicase, the two protein kinases CDK and DDK, as well as MCM10, are required. In addition to the initiation of DNA replication, MCM function must be regulated at the DNA replication steps of elongation and termination. Polyubiquitylation of MCM7 is involved in terminating MCM function. Reinitiation of DNA replication in a single cell cycle, which is prevented mainly by CDK, is understood at the molecular level. MCM2-7 gene expression is regulated during cellular aging and the cell cycle, and the expression depends on oxygen concentration. These regulatory processes have been described recently. Genomic structural alteration, which is an essential element in cancer progression, is mainly generated by disruptions of DNA replication fork structures. A point mutation in MCM4 that disturbs MCM2-7 function results in genomic instability, leading to the generation of cancer cells. In this review, I focus on the following points: 1) function of the MCM2-7 complex, 2) activation of MCM2-7 helicase, 3) regulation of MCM2-7 function, 4) MCM2-7 expression, and 5) the role of MCM mutation in cancer progression.
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Schumann M, Malešević M, Hinze E, Mathea S, Meleshin M, Schutkowski M, Haehnel W, Schiene-Fischer C. Regulation of the Minichromosome Maintenance Protein 3 (MCM3) Chromatin Binding by the Prolyl Isomerase Pin1. J Mol Biol 2018; 430:5169-5181. [PMID: 30316783 DOI: 10.1016/j.jmb.2018.10.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 09/26/2018] [Accepted: 10/04/2018] [Indexed: 01/16/2023]
Abstract
Human Pin1 is a peptidyl prolyl cis/trans isomerase with a unique preference for phosphorylated Ser/Thr-Pro substrate motifs. Here we report that MCM3 (minichromosome maintenance complex component 3) is a novel target of Pin1. MCM3 interacts directly with the WW domain of Pin1. Proline-directed phosphorylation of MCM3 at S112 and T722 are crucial for the interaction with Pin1. MCM3 as a subunit of the minichromosome maintenance heterocomplex MCM2-7 is part of the pre-replication complex responsible for replication licensing and is implicated in the formation of the replicative helicase during progression of replication. Our data suggest that Pin1 coordinates phosphorylation-dependently MCM3 loading onto chromatin and its unloading from chromatin, thereby mediating S phase control.
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Affiliation(s)
- Michael Schumann
- Department of Enzymology, Institute for Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Str. 3a, D-06120 Halle/Saale, Germany
| | - Miroslav Malešević
- Max Planck Research Unit for Enzymology of Protein Folding Halle, Weinbergweg 22, D-06120 Halle/Saale, Germany
| | - Erik Hinze
- Max Planck Research Unit for Enzymology of Protein Folding Halle, Weinbergweg 22, D-06120 Halle/Saale, Germany
| | - Sebastian Mathea
- Max Planck Research Unit for Enzymology of Protein Folding Halle, Weinbergweg 22, D-06120 Halle/Saale, Germany
| | - Marat Meleshin
- Department of Enzymology, Institute for Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Str. 3a, D-06120 Halle/Saale, Germany
| | - Mike Schutkowski
- Department of Enzymology, Institute for Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Str. 3a, D-06120 Halle/Saale, Germany
| | - Wolfgang Haehnel
- Institute of Biology II / Biochemistry, Albert-Ludwigs-Universität Freiburg, Schänzlestr. 1, D-79104 Freiburg, Germany
| | - Cordelia Schiene-Fischer
- Department of Enzymology, Institute for Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Str. 3a, D-06120 Halle/Saale, Germany.
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21
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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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22
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Gambus A. Termination of Eukaryotic Replication Forks. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1042:163-187. [DOI: 10.1007/978-981-10-6955-0_8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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23
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Coli A, Asa SL, Fadda G, Scannone D, Chiloiro S, De Marinis L, Lauretti L, Ranelletti FO, Lauriola L. Minichromosome maintenance protein 7 as prognostic marker of tumor aggressiveness in pituitary adenoma patients. Eur J Endocrinol 2016; 174:307-14. [PMID: 26620390 DOI: 10.1530/eje-15-0586] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2015] [Accepted: 11/30/2015] [Indexed: 01/05/2023]
Abstract
BACKGROUND Ki-67 labeling index (LI) is currently regarded as a useful prognostic marker of pituitary adenoma (PA) clinical behavior, although its relevance as a reliable clinical indicator is far from being universally accepted, since both validations and criticisms are found in the literature. Minichromosome maintenance 7 (MCM7), a cell-cycle regulator protein, has been recently proposed as a marker of tumor aggressiveness in tumors from many sites, including the CNS. Therefore, we evaluated MCM7, in comparison to Ki-67, as a potential marker of clinical outcome in PA. DESIGN AND METHODS In this single-institution retrospective study, 97 patients with PA (23 ACTH, 12 GH, 29 PRL, 10 FSH/LH, and 23 non-secreting adenomas) were recruited and the prognostic value of both MCM7 and Ki-67 was evaluated by immunohistochemical techniques. In addition, p53 nuclear expression and mitotic index were also evaluated. RESULTS Twenty-six of the 97 PA patients recurred during the follow-up period. Cox's regression analysis showed that high nuclear expression of MCM7 LI, unlike Ki-67 LI, was directly associated with a higher (7.7-fold) risk of recurrence/progression. Kaplan-Meier analysis of recurrence/progression-free survival curves revealed that patients with high MCM7 LI (≥15%) had a shorter recurrence/progression-free survival than those with low MCM7 LI (<15%). Moreover, among patients with invasive tumors, high MCM7 LI identified those with the highest risk of recurrence/progression. CONCLUSIONS Data from this study suggest that MCM7 is a prognostic marker of clinical outcome in PA patients, more reliable and informative than Ki-67.
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Affiliation(s)
- Antonella Coli
- Department of Anatomic PathologyCatholic University, Largo F Vito 1, 00168 Rome, ItalyDepartment of Laboratory Medicine and PathobiologyUniversity of Toronto, Ontario, CanadaDepartments of EndocrinologyNeurosurgeryHistologyCatholic University, Rome, Italy
| | - Sylvia L Asa
- Department of Anatomic PathologyCatholic University, Largo F Vito 1, 00168 Rome, ItalyDepartment of Laboratory Medicine and PathobiologyUniversity of Toronto, Ontario, CanadaDepartments of EndocrinologyNeurosurgeryHistologyCatholic University, Rome, Italy
| | - Guido Fadda
- Department of Anatomic PathologyCatholic University, Largo F Vito 1, 00168 Rome, ItalyDepartment of Laboratory Medicine and PathobiologyUniversity of Toronto, Ontario, CanadaDepartments of EndocrinologyNeurosurgeryHistologyCatholic University, Rome, Italy
| | - Domenico Scannone
- Department of Anatomic PathologyCatholic University, Largo F Vito 1, 00168 Rome, ItalyDepartment of Laboratory Medicine and PathobiologyUniversity of Toronto, Ontario, CanadaDepartments of EndocrinologyNeurosurgeryHistologyCatholic University, Rome, Italy
| | - Sabrina Chiloiro
- Department of Anatomic PathologyCatholic University, Largo F Vito 1, 00168 Rome, ItalyDepartment of Laboratory Medicine and PathobiologyUniversity of Toronto, Ontario, CanadaDepartments of EndocrinologyNeurosurgeryHistologyCatholic University, Rome, Italy
| | - Laura De Marinis
- Department of Anatomic PathologyCatholic University, Largo F Vito 1, 00168 Rome, ItalyDepartment of Laboratory Medicine and PathobiologyUniversity of Toronto, Ontario, CanadaDepartments of EndocrinologyNeurosurgeryHistologyCatholic University, Rome, Italy
| | - Liverana Lauretti
- Department of Anatomic PathologyCatholic University, Largo F Vito 1, 00168 Rome, ItalyDepartment of Laboratory Medicine and PathobiologyUniversity of Toronto, Ontario, CanadaDepartments of EndocrinologyNeurosurgeryHistologyCatholic University, Rome, Italy
| | - Franco O Ranelletti
- Department of Anatomic PathologyCatholic University, Largo F Vito 1, 00168 Rome, ItalyDepartment of Laboratory Medicine and PathobiologyUniversity of Toronto, Ontario, CanadaDepartments of EndocrinologyNeurosurgeryHistologyCatholic University, Rome, Italy
| | - Libero Lauriola
- Department of Anatomic PathologyCatholic University, Largo F Vito 1, 00168 Rome, ItalyDepartment of Laboratory Medicine and PathobiologyUniversity of Toronto, Ontario, CanadaDepartments of EndocrinologyNeurosurgeryHistologyCatholic University, Rome, Italy
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24
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Doellinger J, Schaade L, Nitsche A. Comparison of the Cowpox Virus and Vaccinia Virus Mature Virion Proteome: Analysis of the Species- and Strain-Specific Proteome. PLoS One 2015; 10:e0141527. [PMID: 26556597 PMCID: PMC4640714 DOI: 10.1371/journal.pone.0141527] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 10/09/2015] [Indexed: 01/29/2023] Open
Abstract
Cowpox virus (CPXV) causes most zoonotic orthopoxvirus (OPV) infections in Europe and Northern as well as Central Asia. The virus has the broadest host range of OPV and is transmitted to humans from rodents and other wild or domestic animals. Increasing numbers of human CPXV infections in a population with declining immunity have raised concerns about the virus' zoonotic potential. While there have been reports on the proteome of other human-pathogenic OPV, namely vaccinia virus (VACV) and monkeypox virus (MPXV), the protein composition of the CPXV mature virion (MV) is unknown. This study focused on the comparative analysis of the VACV and CPXV MV proteome by label-free single-run proteomics using nano liquid chromatography and high-resolution tandem mass spectrometry (nLC-MS/MS). The presented data reveal that the common VACV and CPXV MV proteome contains most of the known conserved and essential OPV proteins and is associated with cellular proteins known to be essential for viral replication. While the species-specific proteome could be linked mainly to less genetically-conserved gene products, the strain-specific protein abundance was found to be of high variance in proteins associated with entry, host-virus interaction and protein processing.
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Affiliation(s)
- Joerg Doellinger
- Centre for Biological Threats and Special Pathogens, Highly Pathogenic Viruses (ZBS1), Robert Koch Institute, Berlin, Germany
- * E-mail:
| | - Lars Schaade
- Centre for Biological Threats and Special Pathogens, Highly Pathogenic Viruses (ZBS1), Robert Koch Institute, Berlin, Germany
| | - Andreas Nitsche
- Centre for Biological Threats and Special Pathogens, Highly Pathogenic Viruses (ZBS1), Robert Koch Institute, Berlin, Germany
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25
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Håland TW, Boye E, Stokke T, Grallert B, Syljuåsen RG. Simultaneous measurement of passage through the restriction point and MCM loading in single cells. Nucleic Acids Res 2015; 43:e150. [PMID: 26250117 PMCID: PMC4678840 DOI: 10.1093/nar/gkv744] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 07/12/2015] [Indexed: 12/14/2022] Open
Abstract
Passage through the Retinoblastoma protein (RB1)-dependent restriction point and the loading of minichromosome maintenance proteins (MCMs) are two crucial events in G1-phase that help maintain genome integrity. Deregulation of these processes can cause uncontrolled proliferation and cancer development. Both events have been extensively characterized individually, but their relative timing and inter-dependence remain less clear. Here, we describe a novel method to simultaneously measure MCM loading and passage through the restriction point. We exploit that the RB1 protein is anchored in G1-phase but is released when hyper-phosphorylated at the restriction point. After extracting cells with salt and detergent before fixation we can simultaneously measure, by flow cytometry, the loading of MCMs onto chromatin and RB1 binding to determine the order of the two events in individual cells. We have used this method to examine the relative timing of the two events in human cells. Whereas in BJ fibroblasts released from G0-phase MCM loading started mainly after the restriction point, in a significant fraction of exponentially growing BJ and U2OS osteosarcoma cells MCMs were loaded in G1-phase with RB1 anchored, demonstrating that MCM loading can also start before the restriction point. These results were supported by measurements in synchronized U2OS cells.
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Affiliation(s)
- T W Håland
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0316 Oslo, Norway
| | - E Boye
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0316 Oslo, Norway
| | - T Stokke
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway
| | - B Grallert
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway
| | - R G Syljuåsen
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway
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26
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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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Abstract
To ensure duplication of the entire genome, eukaryotic DNA replication initiates from thousands of replication origins. The replication forks move through the chromatin until they encounter forks from neighboring origins. During replication fork termination forks converge, the replisomes disassemble and topoisomerase II resolves the daughter DNA molecules. If not resolved efficiently, terminating forks result in genomic instability through the formation of pathogenic structures. Our recent findings shed light onto the mechanism of replisome disassembly upon replication fork termination. We have shown that termination-specific polyubiquitylation of the replicative helicase component – Mcm7, leads to dissolution of the active helicase in a process dependent on the p97/VCP/Cdc48 segregase. The inhibition of terminating helicase disassembly resulted in a replication termination defect. In this extended view we present hypothetical models of replication fork termination and discuss remaining and emerging questions in the DNA replication termination field.
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Key Words
- CMG, Cdc45, Mcm2–7, GINS complex
- CRL, cullin-RING ligase
- D loop, displacement loop
- DDR, DNA damage response
- DNA replication
- DSB, double strand break
- DUB, deubiquitylating enzyme
- ER, endoplasmic reticulum
- ERAD, endoplasmic reticulum associated protein degradation
- GINS, Go-Ichi-Ni-San, complex made of Sld5, Psf1, Psf2, Psf3
- ICL, intra-strand crosslink
- MCM, Minichromosome maintenance
- Mcm2–7
- OriC, chromosomal replication origin
- R loop, RNA:DNA hybrid
- RING, really interesting gene
- RPC, Replisome Progression Complex
- Ter, termination site
- Tus-Ter, terminus utilisation substance - termination
- Xenopus
- p97 segregase
- replication termination
- replicative helicase
- replisome
- ubiquitin
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Affiliation(s)
- Rachael Bailey
- a School of Cancer Sciences; University of Birmingham ; Birmingham , UK
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28
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Abstract
The initiation of eukaryotic DNA replication is a highly regulated process conserved from yeast to human. The past decade has seen significant advances in understanding how the CMG (Cdc45‐MCM‐GINS) replicative helicase is loaded onto DNA. However, very little was known on how this complex is removed from chromatin at the end of S phase. Two papers in a recent issue of Science [1], [2] show that in yeast and in Xenopus, the CMG complex is unloaded at replication termination sites by an active mechanism involving the polyubiquitylation of Mcm7.
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Moreno SP, Bailey R, Campion N, Herron S, Gambus A. Polyubiquitylation drives replisome disassembly at the termination of DNA replication. Science 2014; 346:477-81. [PMID: 25342805 DOI: 10.1126/science.1253585] [Citation(s) in RCA: 141] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Resolution of replication forks during termination of DNA replication is essential for accurate duplication of eukaryotic genomes. Here we present evidence consistent with the idea that polyubiquitylation of a replisome component (Mcm7) leads to its disassembly at the converging terminating forks because of the action of the p97/VCP/Cdc48 protein remodeler. Using Xenopus laevis egg extract, we have shown that blocking polyubiquitylation results in the prolonged association of the active helicase with replicating chromatin. The Mcm7 subunit is the only component of the active helicase that we find polyubiquitylated during replication termination. The observed polyubiquitylation is followed by disassembly of the active helicase dependent on p97/VCP/Cdc48. Altogether, our data provide insight into the mechanism of replisome disassembly during eukaryotic DNA replication termination.
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Affiliation(s)
- Sara Priego Moreno
- School of Cancer Sciences, University of Birmingham, Vincent Drive, Birmingham B15 2TT, UK
| | - Rachael Bailey
- School of Cancer Sciences, University of Birmingham, Vincent Drive, Birmingham B15 2TT, UK
| | - Nicholas Campion
- School of Cancer Sciences, University of Birmingham, Vincent Drive, Birmingham B15 2TT, UK
| | - Suzanne Herron
- School of Cancer Sciences, University of Birmingham, Vincent Drive, Birmingham B15 2TT, UK
| | - Agnieszka Gambus
- School of Cancer Sciences, University of Birmingham, Vincent Drive, Birmingham B15 2TT, UK.
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30
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Maric M, Maculins T, De Piccoli G, Labib K. Cdc48 and a ubiquitin ligase drive disassembly of the CMG helicase at the end of DNA replication. Science 2014; 346:1253596. [PMID: 25342810 PMCID: PMC4300516 DOI: 10.1126/science.1253596] [Citation(s) in RCA: 174] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Chromosome replication is initiated by a universal mechanism in eukaryotic cells, involving the assembly and activation at replication origins of the CMG (Cdc45-MCM-GINS) DNA helicase, which is essential for the progression of replication forks. Disassembly of CMG is likely to be a key regulated step at the end of chromosome replication, but the mechanism was unknown until now. Here we show that the ubiquitin ligase known as SCF(Dia2) promotes ubiquitylation of CMG during the final stages of chromosome replication in Saccharomyces cerevisiae. The Cdc48/p97 segregase then associates with ubiquitylated CMG, leading rapidly to helicase disassembly. These findings indicate that the end of chromosome replication in eukaryotes is controlled in a similarly complex fashion to the much-better-characterized initiation step.
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Affiliation(s)
- Marija Maric
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
- Cancer Research UK Manchester Institute, University of Manchester, Wilmslow Road, Manchester M20 4BX, UK
| | - Timurs Maculins
- Cancer Research UK Manchester Institute, University of Manchester, Wilmslow Road, Manchester M20 4BX, UK
| | - Giacomo De Piccoli
- Cancer Research UK Manchester Institute, University of Manchester, Wilmslow Road, Manchester M20 4BX, UK
| | - Karim Labib
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
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31
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Affiliation(s)
- Stephen P. Bell
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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32
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MCM Paradox: Abundance of Eukaryotic Replicative Helicases and Genomic Integrity. Mol Biol Int 2014; 2014:574850. [PMID: 25386362 PMCID: PMC4217321 DOI: 10.1155/2014/574850] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 09/30/2014] [Indexed: 12/03/2022] Open
Abstract
As a crucial component of DNA replication licensing system, minichromosome maintenance (MCM) 2–7 complex acts as the eukaryotic DNA replicative helicase. The six related MCM proteins form a heterohexamer and bind with ORC, CDC6, and Cdt1 to form the prereplication complex. Although the MCMs are well known as replicative helicases, their overabundance and distribution patterns on chromatin present a paradox called the “MCM paradox.” Several approaches had been taken to solve the MCM paradox and describe the purpose of excess MCMs distributed beyond the replication origins. Alternative functions of these MCMs rather than a helicase had also been proposed. This review focuses on several models and concepts generated to solve the MCM paradox coinciding with their helicase function and provides insight into the concept that excess MCMs are meant for licensing dormant origins as a backup during replication stress. Finally, we extend our view towards the effect of alteration of MCM level. Though an excess MCM constituent is needed for normal cells to withstand stress, there must be a delineation of the threshold level in normal and malignant cells. This review also outlooks the future prospects to better understand the MCM biology.
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33
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Molecular mechanisms of DNA replication checkpoint activation. Genes (Basel) 2014; 5:147-75. [PMID: 24705291 PMCID: PMC3978517 DOI: 10.3390/genes5010147] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 02/20/2014] [Accepted: 02/21/2014] [Indexed: 01/27/2023] Open
Abstract
The major challenge of the cell cycle is to deliver an intact, and fully duplicated, genetic material to the daughter cells. To this end, progression of DNA synthesis is monitored by a feedback mechanism known as replication checkpoint that is untimely linked to DNA replication. This signaling pathway ensures coordination of DNA synthesis with cell cycle progression. Failure to activate this checkpoint in response to perturbation of DNA synthesis (replication stress) results in forced cell division leading to chromosome fragmentation, aneuploidy, and genomic instability. In this review, we will describe current knowledge of the molecular determinants of the DNA replication checkpoint in eukaryotic cells and discuss a model of activation of this signaling pathway crucial for maintenance of genomic stability.
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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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35
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Latreille D, Bluy L, Benkirane M, Kiernan RE. Identification of histone 3 variant 2 interacting factors. Nucleic Acids Res 2014; 42:3542-50. [PMID: 24393775 PMCID: PMC3973350 DOI: 10.1093/nar/gkt1355] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The epigenome is defined as a type of information that can be transmitted independently of the DNA sequence, at the chromatin level, through post-translational modifications present on histone tails. Recent advances in the identification of histone 3 variants suggest a new model of information transmission through deposition of specific histone variants. To date, several non-centromeric histone 3 variants have been identified in mammals. Despite protein sequence similarity, specific deposition complexes have been characterized for both histone 3.1 (H3.1) and histone 3.3 (H3.3), whereas no deposition complex for histone 3.2 (H3.2) has been identified to date. Here, we identified human H3.2 partners by immunopurification of nuclear H3.2 complexes followed by mass spectrometry analysis. Further biochemical analyses highlighted two major complexes associated with H3.2, one containing chromatin associated factor-1 subunits and the other consisting of a subcomplex of mini chromosome maintenance helicases, together with Asf1. The purified complexes could associate with a DNA template in vitro.
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Affiliation(s)
- Daniel Latreille
- Laboratoire de Régulation des Gènes, Institut de Génétique Humaine, CNRS UPR1142, Montpellier 34396, France and Laboratoire de Virologie Moléculaire, Institut de Génétique Humaine, CNRS UPR1142, Montpellier 34396, France
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36
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Tiengwe C, Marques CA, McCulloch R. Nuclear DNA replication initiation in kinetoplastid parasites: new insights into an ancient process. Trends Parasitol 2013; 30:27-36. [PMID: 24287149 DOI: 10.1016/j.pt.2013.10.009] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 10/28/2013] [Accepted: 10/30/2013] [Indexed: 12/23/2022]
Abstract
Nuclear DNA replication is, arguably, the central cellular process in eukaryotes, because it drives propagation of life and intersects with many other genome reactions. Perhaps surprisingly, our understanding of nuclear DNA replication in kinetoplastids was limited until a clutch of studies emerged recently, revealing new insight into both the machinery and genome-wide coordination of the reaction. Here, we discuss how these studies suggest that the earliest acting components of the kinetoplastid nuclear DNA replication machinery - the factors that demarcate sites of the replication initiation, termed origins - are diverged from model eukaryotes. In addition, we discuss how origin usage and replication dynamics relate to the highly unusual organisation of transcription in the genome of Trypanosoma brucei.
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Affiliation(s)
- Calvin Tiengwe
- The University of Glasgow, Wellcome Trust Centre for Molecular Parasitology and Institute of Infection, Immunity and Inflammation, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK; The Johns Hopkins University School of Medicine, Department of Cell Biology, Baltimore, MD, USA
| | - Catarina A Marques
- The University of Glasgow, Wellcome Trust Centre for Molecular Parasitology and Institute of Infection, Immunity and Inflammation, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
| | - Richard McCulloch
- The University of Glasgow, Wellcome Trust Centre for Molecular Parasitology and Institute of Infection, Immunity and Inflammation, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK.
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37
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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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38
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Nishiyama A, Yamaguchi L, Sharif J, Johmura Y, Kawamura T, Nakanishi K, Shimamura S, Arita K, Kodama T, Ishikawa F, Koseki H, Nakanishi M. Uhrf1-dependent H3K23 ubiquitylation couples maintenance DNA methylation and replication. Nature 2013; 502:249-53. [DOI: 10.1038/nature12488] [Citation(s) in RCA: 252] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 07/18/2013] [Indexed: 12/18/2022]
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39
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Abstract
DNA replication is tightly controlled in eukaryotic cells to ensure that an exact copy of the genetic material is inherited by both daughter cells. Oscillating waves of cyclin-dependent kinase (CDK) and anaphase-promoting complex/cyclosome (APC/C) activities provide a binary switch that permits the replication of each chromosome exactly once per cell cycle. Work from several organisms has revealed a conserved strategy whereby inactive replication complexes are assembled onto DNA during periods of low CDK and high APC activity but are competent to execute genome duplication only when these activities are reversed. Periods of high CDK and low APC/C serve an essential function by blocking reassembly of replication complexes, thereby preventing rereplication. Higher eukaryotes have evolved additional CDK-independent mechanisms for preventing rereplication.
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Affiliation(s)
- Khalid Siddiqui
- Cancer Research UK, London Research Institute, Clare Hall Laboratories, South Mimms, Herts EN6 3LD, United Kingdom
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40
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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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41
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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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42
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Foxn1 maintains thymic epithelial cells to support T-cell development via mcm2 in zebrafish. Proc Natl Acad Sci U S A 2012; 109:21040-5. [PMID: 23213226 DOI: 10.1073/pnas.1217021110] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The thymus is mainly comprised of thymic epithelial cells (TECs), which form the unique thymic epithelial microenvironment essential for intrathymic T-cell development. Foxn1, a member of the forkhead transcription factor family, is required for establishing a functional thymic rudiment. However, the molecular mechanisms underlying the function of Foxn1 are still largely unclear. Here, we show that Foxn1 functions in thymus development through Mcm2 in the zebrafish. We demonstrate that, in foxn1 knockdown embryos, the thymic rudiment is reduced and T-cell development is impaired. Genome-wide expression profiling shows that a number of genes, including some known thymopoiesis genes, are dysregulated during the initiation of the thymus primordium and immigration of T-cell progenitors to the thymus. Functional and epistatic studies show that mcm2 and cdca7 are downstream of Foxn1, and mcm2 is a direct target gene of Foxn1 in TECs. Finally, we find that the thymus defects in foxn1 and mcm2 morphants might be attributed to reduced cell proliferation rather than apoptosis. Our results reveal that the foxn1-mcm2 axis plays a central role in the genetic regulatory network controlling thymus development in zebrafish.
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43
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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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44
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Aparicio T, Megías D, Méndez J. Visualization of the MCM DNA helicase at replication factories before the onset of DNA synthesis. Chromosoma 2012; 121:499-507. [PMID: 22911457 DOI: 10.1007/s00412-012-0381-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 08/09/2012] [Accepted: 08/09/2012] [Indexed: 10/28/2022]
Abstract
In mammalian cells, DNA synthesis takes place at defined nuclear structures termed "replication foci" (RF) that follow the same order of activation in each cell cycle. Intriguingly, immunofluorescence studies have failed to visualize the DNA helicase minichromosome maintenance (MCM) at RF, raising doubts about its physical presence at the sites of DNA synthesis. We have revisited this paradox by pulse-labeling RF during the S phase and analyzing the localization of MCM at labeled DNA in the following cell cycle. Using high-throughput confocal microscopy, we provide direct evidence that MCM proteins concentrate in G1 at the chromosome structures bound to become RF in the S phase. Upon initiation of DNA synthesis, an active "MCM eviction" mechanism contributes to reduce the excess of DNA helicases at RF. Most MCM complexes are released from chromatin, except for a small but detectable fraction that remains at the forks during the S phase, as expected for a replicative helicase.
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Affiliation(s)
- Tomás Aparicio
- DNA Replication Group, Molecular Oncology Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro, 3, 28029, Madrid, Spain
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45
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Watanabe E, Ohara R, Ishimi Y. Effect of an MCM4 mutation that causes tumours in mouse on human MCM4/6/7 complex formation. J Biochem 2012; 152:191-8. [PMID: 22668557 DOI: 10.1093/jb/mvs060] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
It has been reported that a point mutation of minichromosome maintenance (MCM)4 causes mammary carcinoma, and it deregulates DNA replication to produce abnormal chromosome structures. To understand the effect of this mutation at level of MCM2-7 interaction, we examined the effect of the same mutation of human MCM4 on the complex formation with MCM6 and MCM7 in insect cells. Human MCM4/6/7 complexes containing the mutated MCM4 were formed, but the hexameric complex formation was not evident in comparison with those containing wild-type MCM4. In binary expression of MCM4 and MCM6, decreased levels of MCM6 were recovered with the mutated MCM4, compared with wild-type MCM4. These results suggest that this mutation of MCM4 perturbs proper interaction with MCM6 to affect complex formation of MCM4/6/7 that is a core structure of MCM2-7 complex. Consistent with this notion, nuclear localization and MCM complex formation of forcedly expressed MCM4 in human cells are affected by this mutation. Thus, the defect of this mutant MCM4 in interacting with MCM6 may generate a decreased level of chromatin binding of MCM2-7 complex.
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Affiliation(s)
- Emi Watanabe
- College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 351-8511, Japan
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46
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Quimbaya M, Vandepoele K, Raspé E, Matthijs M, Dhondt S, Beemster GTS, Berx G, De Veylder L. Identification of putative cancer genes through data integration and comparative genomics between plants and humans. Cell Mol Life Sci 2012; 69:2041-55. [PMID: 22218400 PMCID: PMC11114995 DOI: 10.1007/s00018-011-0909-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Revised: 12/11/2011] [Accepted: 12/13/2011] [Indexed: 11/27/2022]
Abstract
Coordination of cell division with growth and development is essential for the survival of organisms. Mistakes made during replication of genetic material can result in cell death, growth defects, or cancer. Because of the essential role of the molecular machinery that controls DNA replication and mitosis during development, its high degree of conservation among organisms is not surprising. Mammalian cell cycle genes have orthologues in plants, and vice versa. However, besides the many known and characterized proliferation genes, still undiscovered regulatory genes are expected to exist with conserved functions in plants and humans. Starting from genome-wide Arabidopsis thaliana microarray data, an integrative strategy based on coexpression, functional enrichment analysis, and cis-regulatory element annotation was combined with a comparative genomics approach between plants and humans to detect conserved cell cycle genes involved in DNA replication and/or DNA repair. With this systemic strategy, a set of 339 genes was identified as potentially conserved proliferation genes. Experimental analysis confirmed that 20 out of 40 selected genes had an impact on plant cell proliferation; likewise, an evolutionarily conserved role in cell division was corroborated for two human orthologues. Moreover, association analysis integrating Homo sapiens gene expression data with clinical information revealed that, for 45 genes, altered transcript levels and relapse risk clearly correlated. Our results illustrate how a systematic exploration of the A. thaliana genome can contribute to the experimental identification of new cell cycle regulators that might represent novel oncogenes or/and tumor suppressors.
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Affiliation(s)
- Mauricio Quimbaya
- Department of Plant Systems Biology, VIB, Technologiepark 927, 9052 Gent, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, 9052 Gent, Belgium
- Molecular and Cellular Oncology Unit, Department for Molecular Biomedical Research, VIB, Technologiepark 927, 9052 Gent, Belgium
- Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, 9052 Gent, Belgium
| | - Klaas Vandepoele
- Department of Plant Systems Biology, VIB, Technologiepark 927, 9052 Gent, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, 9052 Gent, Belgium
| | - Eric Raspé
- Molecular and Cellular Oncology Unit, Department for Molecular Biomedical Research, VIB, Technologiepark 927, 9052 Gent, Belgium
- Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, 9052 Gent, Belgium
| | - Michiel Matthijs
- Department of Plant Systems Biology, VIB, Technologiepark 927, 9052 Gent, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, 9052 Gent, Belgium
| | - Stijn Dhondt
- Department of Plant Systems Biology, VIB, Technologiepark 927, 9052 Gent, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, 9052 Gent, Belgium
| | - Gerrit T. S. Beemster
- Department of Plant Systems Biology, VIB, Technologiepark 927, 9052 Gent, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, 9052 Gent, Belgium
- Department of Biology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerpen, Belgium
| | - Geert Berx
- Molecular and Cellular Oncology Unit, Department for Molecular Biomedical Research, VIB, Technologiepark 927, 9052 Gent, Belgium
- Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, 9052 Gent, Belgium
| | - Lieven De Veylder
- Department of Plant Systems Biology, VIB, Technologiepark 927, 9052 Gent, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, 9052 Gent, Belgium
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47
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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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48
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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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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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50
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Abstract
In eukaryotes, the Mcm2-7 complex forms the core of the replicative helicase - the molecular motor that uses ATP binding and hydrolysis to fuel the unwinding of double-stranded DNA at the replication fork. Although it is a toroidal hexameric helicase superficially resembling better-studied homohexameric helicases from prokaryotes and viruses, Mcm2-7 is the only known helicase formed from six unique and essential subunits. Recent biochemical and structural analyses of both Mcm2-7 and a higher-order complex containing additional activator proteins (the CMG complex) shed light on the reason behind this unique subunit assembly: whereas only a limited number of specific ATPase active sites are needed for DNA unwinding, one particular ATPase active site has evolved to form a reversible discontinuity (gate) in the toroidal complex. The activation of Mcm2-7 helicase during S-phase requires physical association of the accessory proteins Cdc45 and GINS; structural data suggest that these accessory factors activate DNA unwinding through closure of the Mcm2-7 gate. Moreover, studies capitalizing on advances in the biochemical reconstitution of eukaryotic DNA replication demonstrate that Mcm2-7 loads onto origins during initiation as a double hexamer, yet does not act as a double-stranded DNA pump during elongation.
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Affiliation(s)
- Sriram Vijayraghavan
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, 15260, USA
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