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Li Y, Gao W, Yang Z, Hu Z, Li J. Multi-omics pan-cancer analyses identify MCM4 as a promising prognostic and diagnostic biomarker. Sci Rep 2024; 14:6517. [PMID: 38499612 PMCID: PMC10948783 DOI: 10.1038/s41598-024-57299-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 03/16/2024] [Indexed: 03/20/2024] Open
Abstract
Minichromosome Maintenance Complex Component 4 (MCM4) is a vital component of the mini-chromosome maintenance complex family, crucial for initiating the replication of eukaryotic genomes. Recently, there has been a growing interest in investigating the significance of MCM4 in different types of cancer. Despite the existing research on this topic, a comprehensive analysis of MCM4 across various cancer types has been lacking. This study aims to bridge this knowledge gap by presenting a thorough pan-cancer analysis of MCM4, shedding light on its functional implications and potential clinical applications. The study utilized multi-omics samples from various databases. Bioinformatic tools were employed to explore the expression profiles, genetic alterations, phosphorylation states, immune cell infiltration patterns, immune subtypes, functional enrichment, disease prognosis, as well as the diagnostic potential of MCM4 and its responsiveness to drugs in a range of cancers. Our research demonstrates that MCM4 is closely associated with the oncogenesis, prognosis and diagnosis of various tumors and proposes that MCM4 may function as a potential biomarker in pan-cancer, providing a deeper understanding of its potential role in cancer development and treatment.
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Affiliation(s)
- Yanxing Li
- Xi'an Jiaotong University Health Science Center, Xi'an, 710000, Shaanxi, People's Republic of China
| | - Wentao Gao
- Xi'an Jiaotong University Health Science Center, Xi'an, 710000, Shaanxi, People's Republic of China
| | - Zhen Yang
- Xi'an Jiaotong University Health Science Center, Xi'an, 710000, Shaanxi, People's Republic of China
| | - Zhenwei Hu
- Xi'an Jiaotong University Health Science Center, Xi'an, 710000, Shaanxi, People's Republic of China
| | - Jianjun Li
- Department of Cardiology, Jincheng People's Hospital Affiliated to Changzhi Medical College, Jincheng, Shanxi, People's Republic of China.
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Li Y, Zhu J, Yu Z, Li H, Jin X. The role of Lamin B2 in human diseases. Gene 2023; 870:147423. [PMID: 37044185 DOI: 10.1016/j.gene.2023.147423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 04/02/2023] [Accepted: 04/05/2023] [Indexed: 04/14/2023]
Abstract
Lamin B2 (LMNB2), on the inner side of the nuclear envelope, constitutes the nuclear skeleton by connecting with other nuclear proteins. LMNB2 is involved in a wide range of nuclear functions, including DNA replication and stability, regulation of chromatin, and nuclear stiffness. Moreover, LMNB2 regulates several cellular processes, such as tissue development, cell cycle, cellular proliferation and apoptosis, chromatin localization and stability, and DNA methylation. Besides, the influence of abnormal expression and mutations of LMNB2 has been gradually discovered in cancers and laminopathies. Therefore, this review summarizes the recent advances of LMNB2-associated biological roles in physiological or pathological conditions, with a particular emphasis on cancers and laminopathies, as well as the potential mechanism of LMNB2 in related cancers.
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Affiliation(s)
- Yuxuan Li
- Department of Hepatobiliary and Pancreatic Surgery, Ningbo Medical Center of LiHuiLi Hospital, Ningbo University, Ningbo, Zhejiang 315040, P.R. China; Department of Biochemistry and Molecular Biology, Zhejiang Key Laboratory of Pathophysiology, Health Science Center, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
| | - Jie Zhu
- Department of Hepatobiliary and Pancreatic Surgery, Ningbo Medical Center of LiHuiLi Hospital, Ningbo University, Ningbo, Zhejiang 315040, P.R. China; Department of Biochemistry and Molecular Biology, Zhejiang Key Laboratory of Pathophysiology, Health Science Center, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
| | - Zongdong Yu
- Department of Hepatobiliary and Pancreatic Surgery, Ningbo Medical Center of LiHuiLi Hospital, Ningbo University, Ningbo, Zhejiang 315040, P.R. China; Department of Biochemistry and Molecular Biology, Zhejiang Key Laboratory of Pathophysiology, Health Science Center, Ningbo University, Ningbo, Zhejiang 315211, P.R. China
| | - Hong Li
- Department of Hepatobiliary and Pancreatic Surgery, Ningbo Medical Center of LiHuiLi Hospital, Ningbo University, Ningbo, Zhejiang 315040, P.R. China; Department of Biochemistry and Molecular Biology, Zhejiang Key Laboratory of Pathophysiology, Health Science Center, Ningbo University, Ningbo, Zhejiang 315211, P.R. China.
| | - Xiaofeng Jin
- Department of Hepatobiliary and Pancreatic Surgery, Ningbo Medical Center of LiHuiLi Hospital, Ningbo University, Ningbo, Zhejiang 315040, P.R. China; Department of Biochemistry and Molecular Biology, Zhejiang Key Laboratory of Pathophysiology, Health Science Center, Ningbo University, Ningbo, Zhejiang 315211, P.R. China.
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3
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You Z, Masai H. Potent DNA strand annealing activity associated with mouse Mcm2∼7 heterohexameric complex. Nucleic Acids Res 2017; 45:6494-6506. [PMID: 28449043 PMCID: PMC5499727 DOI: 10.1093/nar/gkx269] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 04/05/2017] [Indexed: 01/08/2023] Open
Abstract
Mini-chromosome maintenance (Mcm) is a central component for DNA unwinding reaction during eukaryotic DNA replication. Mcm2∼7, each containing a conserved ATPase motif, form a six subunit-heterohexamer. Although the reconstituted Mcm2∼7–Cdc45–GINS (CMG) complex displays DNA unwinding activity, the Mcm2∼7 complex does not generally exhibit helicase activity under a normal assay condition. We detected a strong DNA strand annealing activity in the purified mouse Mcm2∼7 heterohexamer, which promotes rapid reassociation of displaced complementary single-stranded DNAs, suggesting a potential cause for its inability to exhibit DNA helicase activity. Indeed, DNA unwinding activity of Mcm2∼7 could be detected in the presence of a single-stranded DNA that is complementary to the displaced strand, which would prevent its reannealing to the template. ATPase-deficient mutations in Mcm2, 4, 5 and 6 subunits inactivated the annealing activity, while those in Mcm2 and 5 subunits alone did not. The annealing activity of Mcm2∼7 does not require Mg2+ and ATP, and is adversely inhibited by the presence of high concentration of Mg2+ and ATP while activated by similar concentrations of ADP. Our findings show that the DNA helicase activity of Mcm2∼7 may be masked by its unexpectedly strong annealing activity, and suggest potential physiological roles of strand annealing activity of Mcm during replication stress responses.
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Affiliation(s)
- Zhiying You
- Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, 156-8506, Japan
| | - Hisao Masai
- Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, 156-8506, Japan
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4
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Parker MW, Botchan MR, Berger JM. Mechanisms and regulation of DNA replication initiation in eukaryotes. Crit Rev Biochem Mol Biol 2017; 52:107-144. [PMID: 28094588 DOI: 10.1080/10409238.2016.1274717] [Citation(s) in RCA: 117] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Cellular DNA replication is initiated through the action of multiprotein complexes that recognize replication start sites in the chromosome (termed origins) and facilitate duplex DNA melting within these regions. In a typical cell cycle, initiation occurs only once per origin and each round of replication is tightly coupled to cell division. To avoid aberrant origin firing and re-replication, eukaryotes tightly regulate two events in the initiation process: loading of the replicative helicase, MCM2-7, onto chromatin by the origin recognition complex (ORC), and subsequent activation of the helicase by its incorporation into a complex known as the CMG. Recent work has begun to reveal the details of an orchestrated and sequential exchange of initiation factors on DNA that give rise to a replication-competent complex, the replisome. Here, we review the molecular mechanisms that underpin eukaryotic DNA replication initiation - from selecting replication start sites to replicative helicase loading and activation - and describe how these events are often distinctly regulated across different eukaryotic model organisms.
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Affiliation(s)
- Matthew W Parker
- a Department of Biophysics and Biophysical Chemistry , Johns Hopkins University School of Medicine , Baltimore , MD , USA
| | - Michael R Botchan
- b Department of Molecular and Cell Biology , University of California Berkeley , Berkeley , CA , USA
| | - James M Berger
- a Department of Biophysics and Biophysical Chemistry , Johns Hopkins University School of Medicine , Baltimore , MD , USA
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5
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Yang CC, Suzuki M, Yamakawa S, Uno S, Ishii A, Yamazaki S, Fukatsu R, Fujisawa R, Sakimura K, Tsurimoto T, Masai H. Claspin recruits Cdc7 kinase for initiation of DNA replication in human cells. Nat Commun 2016; 7:12135. [PMID: 27401717 PMCID: PMC4945878 DOI: 10.1038/ncomms12135] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2016] [Accepted: 06/03/2016] [Indexed: 11/09/2022] Open
Abstract
Claspin transmits replication stress signal from ATR to Chk1 effector kinase as a mediator. It also plays a role in efficient replication fork progression during normal growth. Here we have generated conditional knockout of Claspin and show that Claspin knockout mice are dead by E12.5 and Claspin knockout mouse embryonic fibroblast (MEF) cells show defect in S phase. Using the mutant cell lines, we report the crucial roles of the acidic patch (AP) near the C terminus of Claspin in initiation of DNA replication. Cdc7 kinase binds to AP and this binding is required for phosphorylation of Mcm. AP is involved also in intramolecular interaction with a N-terminal segment, masking the DNA-binding domain and a newly identified PIP motif, and Cdc7-mediated phosphorylation reduces the intramolecular interaction. Our results suggest a new role of Claspin in initiation of DNA replication during normal S phase through the recruitment of Cdc7 that facilitates phosphorylation of Mcm proteins. Claspin mediates the transmission of a replication-stress signal from ATR to Chk1 and is necessary for efficient fork progression. Here the authors demonstrate that the C-terminal acidic patch is important for this role due to its interaction with Cdc7.
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Affiliation(s)
- Chi-Chun Yang
- Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, 4-6-1 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
| | - Masahiro Suzuki
- Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, 4-6-1 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
| | - Shiori Yamakawa
- Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, 4-6-1 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
| | - Syuzi Uno
- Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, 4-6-1 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
| | - Ai Ishii
- Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, 4-6-1 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
| | - Satoshi Yamazaki
- Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, 4-6-1 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
| | - Rino Fukatsu
- Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, 4-6-1 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
| | - Ryo Fujisawa
- Department of Biology, Faculty of Science, Kyushu University 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Kenji Sakimura
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata 951-8585, Japan
| | - Toshiki Tsurimoto
- Department of Biology, Faculty of Science, Kyushu University 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Hisao Masai
- Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, 4-6-1 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
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6
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7
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Hesketh EL, Parker-Manuel RP, Chaban Y, Satti R, Coverley D, Orlova EV, Chong JPJ. DNA induces conformational changes in a recombinant human minichromosome maintenance complex. J Biol Chem 2015; 290:7973-9. [PMID: 25648893 PMCID: PMC4367295 DOI: 10.1074/jbc.m114.622738] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
ATP-dependent DNA unwinding activity has been demonstrated for recombinant archaeal homohexameric minichromosome maintenance (MCM) complexes and their yeast heterohexameric counterparts, but in higher eukaryotes such as Drosophila, MCM-associated DNA helicase activity has been observed only in the context of a co-purified Cdc45-MCM-GINS complex. Here, we describe the production of the recombinant human MCM (hMCM) complex in Escherichia coli. This protein displays ATP hydrolysis activity and is capable of unwinding duplex DNA. Using single-particle asymmetric EM reconstruction, we demonstrate that recombinant hMCM forms a hexamer that undergoes a conformational change when bound to DNA. Recombinant hMCM produced without post-translational modifications is functional in vitro and provides an important tool for biochemical reconstitution of the human replicative helicase.
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Affiliation(s)
- Emma L Hesketh
- From the Department of Biology, University of York, York YO10 5DD and
| | | | - Yuriy Chaban
- the Department of Crystallography, Birkbeck College London, London WC1E 7HX, United Kingdom
| | - Rabab Satti
- From the Department of Biology, University of York, York YO10 5DD and
| | - Dawn Coverley
- From the Department of Biology, University of York, York YO10 5DD and
| | - Elena V Orlova
- the Department of Crystallography, Birkbeck College London, London WC1E 7HX, United Kingdom
| | - James P J Chong
- From the Department of Biology, University of York, York YO10 5DD and
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8
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Petojevic T, Pesavento JJ, Costa A, Liang J, Wang Z, Berger JM, Botchan MR. Cdc45 (cell division cycle protein 45) guards the gate of the Eukaryote Replisome helicase stabilizing leading strand engagement. Proc Natl Acad Sci U S A 2015; 112:E249-58. [PMID: 25561522 PMCID: PMC4311868 DOI: 10.1073/pnas.1422003112] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
DNA replication licensing is now understood to be the pathway that leads to the assembly of double hexamers of minichromosome maintenance (Mcm2-7) at origin sites. Cell division control protein 45 (Cdc45) and GINS proteins activate the latent Mcm2-7 helicase by inducing allosteric changes through binding, forming a Cdc45/Mcm2-7/GINS (CMG) complex that is competent to unwind duplex DNA. The CMG has an active gate between subunits Mcm2 and Mcm5 that opens and closes in response to nucleotide binding. The consequences of inappropriate Mcm2/5 gate actuation and the role of a side channel formed between GINS/Cdc45 and the outer edge of the Mcm2-7 ring for unwinding have remained unexplored. Here we uncover a novel function for Cdc45. Cross-linking studies trace the path of the DNA with the CMG complex at a fork junction between duplex and single strands with the bound CMG in an open or closed gate conformation. In the closed state, the lagging strand does not pass through the side channel, but in the open state, the leading strand surprisingly interacts with Cdc45. Mutations in the recombination protein J fold of Cdc45 that ablate this interaction diminish helicase activity. These data indicate that Cdc45 serves as a shield to guard against occasional slippage of the leading strand from the core channel.
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Affiliation(s)
- Tatjana Petojevic
- Department of Molecular and Cell Biology, Division of Biochemistry and Molecular Biology, University of California, Berkeley, CA 94720; Department of Biology, Chemistry and Pharmacy, Institute of Chemistry and Biochemistry, Freie Universität Berlin, 14195 Berlin, Germany
| | - James J Pesavento
- Department of Molecular and Cell Biology, Division of Biochemistry and Molecular Biology, University of California, Berkeley, CA 94720
| | - Alessandro Costa
- Clare Hall Laboratories, London Research Institute, South Mimms, Herts EN6 3LD, United Kingdom; and
| | - Jingdan Liang
- Department of Molecular and Cell Biology, Division of Biochemistry and Molecular Biology, University of California, Berkeley, CA 94720
| | - Zhijun Wang
- Department of Molecular and Cell Biology, Division of Biochemistry and Molecular Biology, University of California, Berkeley, CA 94720
| | - James M Berger
- Department of Biophysics and Biophysical Chemistry, School of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Michael R Botchan
- Department of Molecular and Cell Biology, Division of Biochemistry and Molecular Biology, University of California, Berkeley, CA 94720;
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9
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You Z, De Falco M, Kamada K, Pisani FM, Masai H. The mini-chromosome maintenance (Mcm) complexes interact with DNA polymerase α-primase and stimulate its ability to synthesize RNA primers. PLoS One 2013; 8:e72408. [PMID: 23977294 PMCID: PMC3748026 DOI: 10.1371/journal.pone.0072408] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Accepted: 07/16/2013] [Indexed: 01/14/2023] Open
Abstract
The Mini-chromosome maintenance (Mcm) proteins are essential as central components for the DNA unwinding machinery during eukaryotic DNA replication. DNA primase activity is required at the DNA replication fork to synthesize short RNA primers for DNA chain elongation on the lagging strand. Although direct physical and functional interactions between helicase and primase have been known in many prokaryotic and viral systems, potential interactions between helicase and primase have not been explored in eukaryotes. Using purified Mcm and DNA primase complexes, a direct physical interaction is detected in pull-down assays between the Mcm2∼7 complex and the hetero-dimeric DNA primase composed of the p48 and p58 subunits. The Mcm4/6/7 complex co-sediments with the primase and the DNA polymerase α-primase complex in glycerol gradient centrifugation and forms a Mcm4/6/7-primase-DNA ternary complex in gel-shift assays. Both the Mcm4/6/7 and Mcm2∼7 complexes stimulate RNA primer synthesis by DNA primase in vitro. However, primase inhibits the Mcm4/6/7 helicase activity and this inhibition is abolished by the addition of competitor DNA. In contrast, the ATP hydrolysis activity of Mcm4/6/7 complex is not affected by primase. Mcm and primase proteins mutually stimulate their DNA-binding activities. Our findings indicate that a direct physical interaction between primase and Mcm proteins may facilitate priming reaction by the former protein, suggesting that efficient DNA synthesis through helicase-primase interactions may be conserved in eukaryotic chromosomes.
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Affiliation(s)
- Zhiying You
- Genome Dynamics Project, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
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10
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Uno S, You Z, Masai H. Purification of replication factors using insect and mammalian cell expression systems. Methods 2012; 57:214-21. [PMID: 22800621 DOI: 10.1016/j.ymeth.2012.06.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Revised: 06/12/2012] [Accepted: 06/25/2012] [Indexed: 10/28/2022] Open
Abstract
Purification of factors for DNA replication in an amount sufficient for detailed biochemical characterization is essential to elucidating its mechanisms. Insect cell expression systems are commonly used for purification of the factors proven to be difficult to deal with in bacteria. We describe first the detailed protocols for purification of mammalian Mcm complexes including the Mcm2/3/4/5/6/7 heterohexamer expressed in insect cells. We then describe a convenient and economical system in which large-sized proteins and multi-factor complexes can be transiently overexpressed in human 293T cells and be rapidly purified in a large quantity. We describe various expression vectors and detailed methods for transfection and purification of various replication factors which have been difficult to obtain in a sufficient amount in other systems. Availability of efficient methods to overproduce and purify the proteins that have been challenging would facilitate the enzymatic analyses of the processes of DNA replication.
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Affiliation(s)
- Shuji Uno
- Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
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11
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Kang YH, Munashingha PR, Lee CH, Nguyen TA, Seo YS. Biochemical studies of the Saccharomyces cerevisiae Mph1 helicase on junction-containing DNA structures. Nucleic Acids Res 2011; 40:2089-106. [PMID: 22090425 PMCID: PMC3300029 DOI: 10.1093/nar/gkr983] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Saccharomyces cerevisiae Mph1 is a 3–5′ DNA helicase, required for the maintenance of genome integrity. In order to understand the ATPase/helicase role of Mph1 in genome stability, we characterized its helicase activity with a variety of DNA substrates, focusing on its action on junction structures containing three or four DNA strands. Consistent with its 3′ to 5′ directionality, Mph1 displaced 3′-flap substrates in double-fixed or equilibrating flap substrates. Surprisingly, Mph1 displaced the 5′-flap strand more efficiently than the 3′ flap strand from double-flap substrates, which is not expected for a 3–5′ DNA helicase. For this to occur, Mph1 required a threshold size (>5 nt) of 5′ single-stranded DNA flap. Based on the unique substrate requirements of Mph1 defined in this study, we propose that the helicase/ATPase activity of Mph1 play roles in converting multiple-stranded DNA structures into structures cleavable by processing enzymes such as Fen1. We also found that the helicase activity of Mph1 was used to cause structural alterations required for restoration of replication forks stalled due to damaged template. The helicase properties of Mph1 reported here could explain how it resolves D-loop structure, and are in keeping with a model proposed for the error-free damage avoidance pathway.
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Affiliation(s)
- Young-Hoon Kang
- Department of Biological Sciences, Center for DNA Replication and Genome Instability, Korea Advanced Institute of Science and Technology, Daejeon, 305-701, Korea
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12
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Rajewska M, Wegrzyn K, Konieczny I. AT-rich region and repeated sequences - the essential elements of replication origins of bacterial replicons. FEMS Microbiol Rev 2011; 36:408-34. [PMID: 22092310 DOI: 10.1111/j.1574-6976.2011.00300.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Accepted: 07/07/2011] [Indexed: 11/27/2022] Open
Abstract
Repeated sequences are commonly present in the sites for DNA replication initiation in bacterial, archaeal, and eukaryotic replicons. Those motifs are usually the binding places for replication initiation proteins or replication regulatory factors. In prokaryotic replication origins, the most abundant repeated sequences are DnaA boxes which are the binding sites for chromosomal replication initiation protein DnaA, iterons which bind plasmid or phage DNA replication initiators, defined motifs for site-specific DNA methylation, and 13-nucleotide-long motifs of a not too well-characterized function, which are present within a specific region of replication origin containing higher than average content of adenine and thymine residues. In this review, we specify methods allowing identification of a replication origin, basing on the localization of an AT-rich region and the arrangement of the origin's structural elements. We describe the regularity of the position and structure of the AT-rich regions in bacterial chromosomes and plasmids. The importance of 13-nucleotide-long repeats present at the AT-rich region, as well as other motifs overlapping them, was pointed out to be essential for DNA replication initiation including origin opening, helicase loading and replication complex assembly. We also summarize the role of AT-rich region repeated sequences for DNA replication regulation.
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Affiliation(s)
- Magdalena Rajewska
- Department of Molecular and Cellular Biology, Intercollegiate Faculty of Biotechnology, University of Gdansk, Gdansk, Poland
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13
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Uno S, Masai H. Efficient expression and purification of human replication fork-stabilizing factor, Claspin, from mammalian cells: DNA-binding activity and novel protein interactions. Genes Cells 2011; 16:842-56. [DOI: 10.1111/j.1365-2443.2011.01535.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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14
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Masai H, Matsumoto S, You Z, Yoshizawa-Sugata N, Oda M. Eukaryotic chromosome DNA replication: where, when, and how? Annu Rev Biochem 2010; 79:89-130. [PMID: 20373915 DOI: 10.1146/annurev.biochem.052308.103205] [Citation(s) in RCA: 370] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
DNA replication is central to cell proliferation. Studies in the past six decades since the proposal of a semiconservative mode of DNA replication have confirmed the high degree of conservation of the basic machinery of DNA replication from prokaryotes to eukaryotes. However, the need for replication of a substantially longer segment of DNA in coordination with various internal and external signals in eukaryotic cells has led to more complex and versatile regulatory strategies. The replication program in higher eukaryotes is under a dynamic and plastic regulation within a single cell, or within the cell population, or during development. We review here various regulatory mechanisms that control the replication program in eukaryotes and discuss future directions in this dynamic field.
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Affiliation(s)
- Hisao Masai
- Genome Dynamics Project, Tokyo Metropolitan Institute of Medical Science, Tokyo 156-8506, Japan.
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15
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Abstract
The Mcm2-7 complex serves as the eukaryotic replicative helicase, the molecular motor that both unwinds duplex DNA and powers fork progression during DNA replication. Consistent with its central role in this process, much prior work has illustrated that Mcm2-7 loading and activation are landmark events in the regulation of DNA replication. Unlike any other hexameric helicase, Mcm2-7 is composed of six unique and essential subunits. Although the unusual oligomeric nature of this complex has long hampered biochemical investigations, recent advances with both the eukaryotic as well as the simpler archaeal Mcm complexes provide mechanistic insight into their function. In contrast to better-studied homohexameric helicases, evidence suggests that the six Mcm2-7 complex ATPase active sites are functionally distinct and are likely specialized to accommodate the regulatory constraints of the eukaryotic process.
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Tan BCM, Liu H, Lin CL, Lee SC. Functional cooperation between FACT and MCM is coordinated with cell cycle and differential complex formation. J Biomed Sci 2010; 17:11. [PMID: 20156367 PMCID: PMC2848000 DOI: 10.1186/1423-0127-17-11] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2009] [Accepted: 02/16/2010] [Indexed: 11/18/2022] Open
Abstract
Background Functional cooperation between FACT and the MCM helicase complex constitutes an integral step during DNA replication initiation. However, mode of regulation that underlies the proper functional interaction of FACT and MCM is poorly understood. Methods & Results Here we present evidence indicating that such interaction is coordinated with cell cycle progression and differential complex formation. We first demonstrate the existence of two distinct FACT-MCM subassemblies, FACT-MCM2/4/6/7 and FACT-MCM2/3/4/5. Both complexes possess DNA unwinding activity and are subject to cell cycle-dependent enzymatic regulation. Interestingly, analysis of functional attributes further suggests that they act at distinct, and possibly sequential, steps during origin establishment and replication initiation. Moreover, we show that the phosphorylation profile of the FACT-associated MCM4 undergoes a cell cycle-dependent change, which is directly correlated with the catalytic activity of the FACT-MCM helicase complexes. Finally, at the quaternary structure level, physical interaction between FACT and MCM complexes is generally dependent on persistent cell cycle and further stabilized upon S phase entry. Cessation of mitotic cycle destabilizes the complex formation and likely leads to compromised coordination and activities. Conclusions Together, our results correlate FACT-MCM functionally and temporally with S phase and DNA replication. They further demonstrate that enzymatic activities intrinsically important for DNA replication are tightly controlled at various levels, thereby ensuring proper progression of, as well as exit from, the cell cycle and ultimately euploid gene balance.
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Affiliation(s)
- Bertrand Chin-Ming Tan
- Department of Life Science, College of Medicine, Chang Gung Univeristy, Taoyuan, Taiwan.
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17
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Abstract
The eukaryotic MCM2-7 complex is recruited onto origins of replication during the G1 phase of the cell cycle and acts as the main helicase at the replication fork during the S phase. Over the last few years a number of structural reports on MCM proteins using both electron microscopy and protein crystallography have been published. The crystal structures of two (almost) full-length archaeal homologs provide the first atomic pictures of a MCM helicase. However one of the structures is at low resolution and the other is of an inactive MCM. Moreover, both proteins are monomeric in the crystal, whereas the activity of the complex is critically dependent on oligomerization. Lower resolution structures derived from electron microscopy studies are therefore crucial to complement the crystallographic analysis and to assemble the multimeric complex that is active in the cell. A critical analysis of all the structural results elucidates the potential conformational changes and dynamic behavior of MCM helicase to provide a first insight into the gamut of molecular configurations adopted during the processes of DNA melting and unwinding.
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18
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Matsunaga F, Takemura K, Akita M, Adachi A, Yamagami T, Ishino Y. Localized melting of duplex DNA by Cdc6/Orc1 at the DNA replication origin in the hyperthermophilic archaeon Pyrococcus furiosus. Extremophiles 2009; 14:21-31. [PMID: 19787415 DOI: 10.1007/s00792-009-0284-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2009] [Accepted: 09/14/2009] [Indexed: 10/20/2022]
Abstract
The initiation step is a key process to regulate the frequency of DNA replication. Although recent studies in Archaea defined the origin of DNA replication (oriC) and the Cdc6/Orc1 homolog as an origin recognition protein, the location and mechanism of duplex opening have remained unclear. We have found that Cdc6/Orc1 binds to oriC and unwinds duplex DNA in the hyperthermophilic archaeon Pyrococcus furiosus, by means of a P1 endonuclease assay. A primer extension analysis further revealed that this localized unwinding occurs in the oriC region at a specific site, which is 12-bp long and rich in adenine and thymine. This site is different from the predicted duplex unwinding element (DUE) that we reported previously. We also discovered that Cdc6/Orc1 induces topological changes in supercoiled oriC DNA, and that this process is dependent on the AAA+ domain. These results indicate that topological alterations of oriC DNA by Cdc6/Orc1 introduce a single-stranded region at the 12-mer site, that could possibly serve as an entry point for Mcm helicase.
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Affiliation(s)
- Fujihiko Matsunaga
- Department of Genetic Resources Technology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka, Fukuoka 812-8581, Japan
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19
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Dual DNA unwinding activities of the Rothmund-Thomson syndrome protein, RECQ4. EMBO J 2009; 28:568-77. [PMID: 19177149 DOI: 10.1038/emboj.2009.13] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2008] [Accepted: 01/08/2009] [Indexed: 12/23/2022] Open
Abstract
Human RECQ helicases have been linked to distinct clinical diseases with increased cancer rates and premature ageing. All RECQ proteins, except RECQ4, have been shown to be functional helicases. Mutations in RECQ4 lead to Rothmund-Thomson syndrome (RTS), and mouse models reveal that the conserved helicase motifs are required for avoidance of RTS. Furthermore, the amino (N) terminus of RECQ4 shares homology with yeast DNA replication initiation factor, Sld2, and is vital for embryonic development. Here, in contrast to previous reports, we show that RECQ4 exhibits DNA helicase activity. Importantly, two distinct regions of the protein, the conserved helicase motifs and the Sld2-like N-terminal domain, each independently promote ATP-dependent DNA unwinding. Taken together, our data provide the first biochemical clues underlying the molecular function of RECQ4 in DNA replication and genome maintenance.
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20
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Kanter DM, Bruck I, Kaplan DL. Mcm subunits can assemble into two different active unwinding complexes. J Biol Chem 2008; 283:31172-82. [PMID: 18801730 DOI: 10.1074/jbc.m804686200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The replication fork helicase in eukaryotes is a large complex that is composed of Mcm2-7, Cdc45, and GINS. The Mcm2-7 proteins form a heterohexameric ring that hydrolyzes ATP and provide the motor function for this unwinding complex. A comprehensive study of how individual Mcm subunit biochemical activities relate to unwinding function has not been accomplished. We studied the mechanism of the Mcm4-Mcm6-Mcm7 complex, a useful model system because this complex has helicase activity in vitro. We separately purified each of three Mcm subunits until they were each nuclease-free, and we then examined the biochemical properties of different combinations of Mcm subunits. We found that Mcm4 and Mcm7 form an active unwinding assembly. The addition of Mcm6 to Mcm4/Mcm7 results in the formation of an active Mcm4/Mcm6/Mcm7 helicase assembly. The Mcm4-Mcm7 complex forms a ringed-shaped hexamer that unwinds DNA with 3' to 5' polarity by a steric exclusion mechanism, similar to Mcm4/Mcm6/Mcm7. The Mcm4-Mcm7 complex has a high level of ATPase activity that is further stimulated by DNA. The ability of different Mcm mixtures to form rings or exhibit DNA stimulation of ATPase activity correlates with the ability of these complexes to unwind DNA. The Mcm4/Mcm7 and Mcm4/Mcm6/Mcm7 assemblies can open to load onto circular DNA to initiate unwinding. We conclude that the Mcm subunits are surprisingly flexible and dynamic in their ability to interact with one another to form active unwinding complexes.
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Affiliation(s)
- Diane M Kanter
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235, USA
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21
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Specific mutations within the AT-rich region of a plasmid replication origin affect either origin opening or helicase loading. Proc Natl Acad Sci U S A 2008; 105:11134-9. [PMID: 18685104 DOI: 10.1073/pnas.0805662105] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Prokaryotic and eukaryotic replicons possess a distinctive region containing a higher than average number of adenine and thymine residues (the AT-rich region) where, during the process of replication initiation, the initial destabilization (opening) of the double helix takes place. In many prokaryotic origins, this region consists of repeated 13-mer motifs whose function has not yet been specified. Here we identify specific mutations within the 13-mer sequences of the broad-host-range plasmid RK2 that can result in defective origin opening or that do not affect opening but induce defects in helicase loading. We also show that after the initial recruitment of helicase at the DnaA-box sequences of the plasmid origin, the helicase is translocated to the AT-rich region in a reaction requiring specific sequence of the 13-mers and appropriate facing of the origin motifs. Our results demonstrate that specific sequences within the AT-rich region of a replication origin are required for either origin opening or helicase loading.
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22
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Stefanovic D, Kusic J, Divac A, Tomic B. Formation of noncanonical DNA structures mediated by human ORC4, a protein component of the origin recognition complex. Biochemistry 2008; 47:8760-7. [PMID: 18652488 DOI: 10.1021/bi800684f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Many genomic sequences, DNA replication origins included, contain specific structural motifs prone to alternative base pairing. Structural rearrangements of DNA require specific environmental conditions and could be favored by chemical agents or proteins. To improve our understanding of alternative conformations of origins and the manner in which they form, we have investigated the effect of DNA-binding, AAA+ protein human ORC4 on single-stranded origin DNA or various oligonucleotides. Here we demonstrate that human ORC4 stimulated formation of inter- and intramolecular T.A.T triplexes and created novel structures, such as homoadenine duplexes. Adenine-based structures were held together by Hoogsteen hydrogen bonds, as demonstrated on 7-deaza-dAMP- or dAMP-containing substrates, and characterized by increased thermal stability. Adenine pairing occurred only in the presence of human ORC4, in a neutral buffer supplemented with ATP and Mg (2+) ions. The protein mutant that could not bind ATP was inactive in this reaction. Since the action of human ORC4 could be biologically important, its potential impact on DNA replication is discussed.
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Affiliation(s)
- Dragana Stefanovic
- Institute of Molecular Genetics and Genetic Engineering, Vojvode Stepe 444a, P.O. Box 23, 11010 Belgrade, Serbia.
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23
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You Z, Masai H. Cdt1 forms a complex with the minichromosome maintenance protein (MCM) and activates its helicase activity. J Biol Chem 2008; 283:24469-77. [PMID: 18606811 DOI: 10.1074/jbc.m803212200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Mcm4/6/7 forms a complex possessing DNA helicase activity, suggesting that Mcm may be a central component for the replicative helicase. Although Cdt1 is known to be essential for loading of Mcm onto the chromatin, its precise role in pre-RC formation and replication initiation is unknown. Using purified proteins, we show that Cdt1 forms a complex with Mcm4/6/7, Mcm2/3/4/5/6/7, and Mcm2/4/6/7 in glycerol gradient fractionation through interaction with Mcm2 and Mcm4/6. In the glycerol gradient fractionation, Mcm4/6/7-Cdt1 forms a complex (speculated to be a (Mcm4/6/7)2-Cdt13 assembly) in the presence of ATP, which is significantly larger than the Mcm4/6/7-Cdt1 complex generated in its absence. Furthermore, DNA binding and helicase activities of Mcm4/6/7 are significantly stimulated by Cdt1 protein in vitro. We generated a Cdt1 mutant, which fails to stimulate DNA binding and helicase activities of Mcm4/6/7. This mutant Cdt1 showed reduced interaction with Mcm and is deficient in the formation of a high molecular weight complex with Mcm. Thus, a productive interaction between Cdt1 and MCM appears to be essential for efficient loading of MCM onto template DNA, as well as for the efficient unwinding reaction.
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Affiliation(s)
- Zhiying You
- Genome Dynamics Project, Tokyo Metropolitan Institute of Medical Science, 18-22 Honkomagome 3-chome, Bunkyo-ku, Tokyo 113-8613, Japan
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24
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Komamura-Kohno Y, Tanaka R, Omori A, Kohno T, Ishimi Y. Biochemical characterization of fragmented human MCM2. FEBS J 2008; 275:727-38. [PMID: 18190532 DOI: 10.1111/j.1742-4658.2007.06239.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The molecular dissection of human MCM2, a constituent of MCM2-7 licensing factor complex, was performed to identify the region responsible for its biochemical activities. Partial digestion with trypsin dissected the MCM2 protein into a central region (148-676) containing ATPase motifs and a C-terminal region (677-895). These two fragments, along with three other fragments (148-441, 442-676 and 442-895), were produced using the wheat germ cell-free system and were examined for their ability to inhibit MCM4/6/7 helicase activity. Two fragments (442-895 and 677-895) containing the C-terminus were partly inhibitory to the activity. Further dissection revealed that one fragment (713-895) has strong inhibitory activity. The inhibitory activity of the smaller fragments derived from the C-terminal region correlated with their ability to inhibit SV40 T antigen helicase activity and also with their ability to bind to ssDNA, which has been shown by gel mobility shift analysis. These results strongly suggest that the MCM2 fragments derived from the C-terminal region inhibit DNA helicase activity through their ability to bind to ssDNA. In contrast, two fragments (148-441 and 442-676) from the central region were mainly responsible for the interaction between MCM2 and MCM4, and this was revealed by a pulldown analysis using MCM4 protein beads. Finally, only complete MCM2, not the smaller fragments, could disassemble the MCM4/6/7 hexamer into the MCM2/4/6/7 tetramer.
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Affiliation(s)
- Yuki Komamura-Kohno
- Mitsubishi Kagaku Institute of Life Sciences (MITILS), Machida, Tokyo, Japan
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25
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Bochman ML, Schwacha A. Differences in the single-stranded DNA binding activities of MCM2-7 and MCM467: MCM2 and MCM5 define a slow ATP-dependent step. J Biol Chem 2007; 282:33795-33804. [PMID: 17895243 DOI: 10.1074/jbc.m703824200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The MCM2-7 complex, a hexamer containing six distinct and essential subunits, is postulated to be the eukaryotic replicative DNA helicase. Although all six subunits function at the replication fork, only a specific subcomplex consisting of the MCM4, 6, and 7 subunits (MCM467) and not the MCM2-7 complex exhibits DNA helicase activity in vitro. To understand why MCM2-7 lacks helicase activity and to address the possible function of the MCM2, 3, and 5 subunits, we have compared the biochemical properties of the Saccharomyces cerevisiae MCM2-7 and MCM467 complexes. We demonstrate that both complexes are toroidal and possess a similar ATP-dependent single-stranded DNA (ssDNA) binding activity, indicating that the lack of helicase activity by MCM2-7 is not due to ineffective ssDNA binding. We identify two important differences between them. MCM467 binds dsDNA better than MCM2-7. In addition, we find that the rate of MCM2-7/ssDNA association is slow compared with MCM467; the association rate can be dramatically increased either by preincubation with ATP or by inclusion of mutations that ablate the MCM2/5 active site. We propose that the DNA binding differences between MCM2-7 and MCM467 correspond to a conformational change at the MCM2/5 active site with putative regulatory significance.
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Affiliation(s)
- Matthew L Bochman
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - Anthony Schwacha
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260.
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26
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Haugland GT, Shin JH, Birkeland NK, Kelman Z. Stimulation of MCM helicase activity by a Cdc6 protein in the archaeon Thermoplasma acidophilum. Nucleic Acids Res 2006; 34:6337-44. [PMID: 17108356 PMCID: PMC1669734 DOI: 10.1093/nar/gkl864] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Replicative DNA helicases are ring-shaped hexamers that play an essential role in chromosomal DNA replication. They unwind the two strands of the duplex DNA and provide the single-stranded (ss) DNA substrate for the polymerase. The minichromosome maintenance (MCM) proteins are thought to function as the replicative helicases in eukarya and archaea. The proteins of only a few archaeal organisms have been studied and revealed that although all have similar amino acid sequences and overall structures they differ in their biochemical properties. In this report the biochemical properties of the MCM protein from the archaeon Thermoplasma acidophilum is described. The enzyme has weak helicase activity on a substrate containing only a 3′-ssDNA overhang region and the protein requires a forked DNA structure for efficient helicase activity. It was also found that the helicase activity is stimulated by one of the two T.acidophilum Cdc6 homologues. This is an interesting observation as it is in sharp contrast to observations made with MCM and Cdc6 homologues from other archaea in which the helicase activity is inhibited when bound to Cdc6.
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Affiliation(s)
| | - Jae-Ho Shin
- University of Maryland Biotechnology Institute, Center for Advanced Research in Biotechnology9600 Gudelsky Drive, Rockville, MD 20850, USA
| | | | - Zvi Kelman
- University of Maryland Biotechnology Institute, Center for Advanced Research in Biotechnology9600 Gudelsky Drive, Rockville, MD 20850, USA
- To whom correspondence should be addressed. Tel: +1 240 314 6294; Fax: +1 240 314 6255;
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27
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Minami H, Takahashi J, Suto A, Saitoh Y, Tsutsumi KI. Binding of AlF-C, an Orc1-binding transcriptional regulator, enhances replicator activity of the rat aldolase B origin. Mol Cell Biol 2006; 26:8770-80. [PMID: 16982680 PMCID: PMC1636824 DOI: 10.1128/mcb.00949-06] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
A region encompassing the rat aldolase B gene (aldB) promoter acts as a chromosomal origin of DNA replication (origin) in rat aldolase B-nonexpressing hepatoma cells. To examine replicator function of the aldB origin, we constructed recombinant mouse cell lines in which the rat aldB origin and the mutant derivatives were inserted into the same position at the mouse chromosome 8 by cre-mediated recombination. Nascent strand abundance assays revealed that the rat origin acts as a replicator at the ectopic mouse locus. Mutation of site C in the rat origin, which binds an Orc1-binding protein AlF-C in vitro, resulted in a significant reduction of the replicator activity in the mouse cells. Chromatin immunoprecipitation (ChIP) assays indicated that the reduction of replicator activity was paralleled with the reduced binding of AlF-C and Orc1, suggesting that sequence-specific binding of AlF-C to the ectopic rat origin leads to enhanced replicator activity in cooperation with Orc1. Involvement of AlF-C in replication in vivo was further examined for the aldB origin at its original rat locus and for a different rat origin identified in the present study, which contained an AlF-C-binding site. ChIP assays revealed that both replication origins bind AlF-C and Orc1. We think that the results presented here may represent one mode of origin recognition in mammalian cells.
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Affiliation(s)
- Hiroyuki Minami
- Cryobiosystem Research Center, Iwate University, Ueda, Morioka, Iwate 020-8550, Japan
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28
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Kawasaki Y, Kim HD, Kojima A, Seki T, Sugino A. Reconstitution of Saccharomyces cerevisiae prereplicative complex assembly in vitro. Genes Cells 2006; 11:745-56. [PMID: 16824194 DOI: 10.1111/j.1365-2443.2006.00975.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The assembly of the prereplicative complex (pre-RC) at the origin of replication in eukaryotes is a highly regulated and highly conserved process that plays a critical role in preventing multiple rounds of DNA replication per cell division cycle. This study analyzes the molecular dynamics of the assembly of Saccharomyces cerevisiae pre-RC in vitro using ARS1 plasmid DNA and yeast whole cell extracts. In addition, pre-RC assembly was reconstituted in vitro using ARS1 DNA and purified origin-recognition complex (ORC), Cdc6p and Cdt1p-Mcm2-7p. The results reveal sequential recruitment of ORC, Cdc6p, Cdt1p and Mcm2-7p on to ARS1 DNA. When Mcm2-7p is maximally loaded, Cdc6p and Cdt1p are released, suggesting that these two proteins are co-ordinately regulated during pre-RC assembly. In extracts from sid2-21 mutant cells that are deficient in CDT1, ORC and Cdc6p bind to ARS1 but Cdt1p and Mcm2-7p do not. However, Mcm2-7p does bind in the presence of exogenous Cdt1p or Cdt1p-Mcm2-7p complex. Cdt1p-Mcm2-7p complex, which was purified from G1-, early S or G2/M-arrested cells, exhibits structure-specific DNA binding, interacting only with bubble- or Y-shape-DNA, but the biological significance of this observation is not yet known.
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Affiliation(s)
- Yasuo Kawasaki
- Laboratories for Biomolecular Networks, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamada-oka, Suita, Osaka 565-0871, Japan.
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29
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Ozaki S, Fujimitsu K, Kurumizaka H, Katayama T. The DnaA homolog of the hyperthermophilic eubacterium Thermotoga maritima forms an open complex with a minimal 149-bp origin region in an ATP-dependent manner. Genes Cells 2006; 11:425-38. [PMID: 16611245 DOI: 10.1111/j.1365-2443.2006.00950.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In Escherichia coli, ATP-DnaA, but not ADP-DnaA, forms an initiation complex that undergoes site-specific duplex DNA unwinding, open complex formation. However, it remains unclear how highly the ATP-dependent activation of the initiation factor is conserved in evolution. The hyperthermophile Thermotoga maritima is one of the most ancient eubacteria in evolution. Here, we show that the DnaA homolog (tmaDnaA) of this bacterium forms open complexes with the predicted origin region (tma-oriC) in vitro. TmaDnaA has a strong and specific affinity for ATP/ADP as well as for 12-mer repeating sequences within the tma-oriC. Unlike ADP-tmaDnaA, ATP-tmaDnaA is highly cooperative in DNA binding and forms open complexes in a manner that depends on temperature and the superhelical tension of the tma-oriC-bearing plasmid. The minimal tma-oriC required for unwinding is a 149-bp region containing five repeats of the 12-mer sequence and two AT-rich 9-mer repeats. TmaDnaA-binding to the 12-mer motif provokes DNA bending. The 9-mer region is the duplex-unwinding site. The tmaDnaA-binding and unwinding motifs of tma-oriC share sequence homology with corresponding archaeal and eukaryotic sequences. These findings suggest that the ATP-dependent molecular switch of the initiator and the mechanisms in the replication initiation complex are highly conserved in eubacterial evolution.
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Affiliation(s)
- Shogo Ozaki
- Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
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30
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Tan BCM, Chien CT, Hirose S, Lee SC. Functional cooperation between FACT and MCM helicase facilitates initiation of chromatin DNA replication. EMBO J 2006; 25:3975-85. [PMID: 16902406 PMCID: PMC1560368 DOI: 10.1038/sj.emboj.7601271] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2006] [Accepted: 07/18/2006] [Indexed: 01/21/2023] Open
Abstract
Chromatin is suppressive in nature to cellular enzymes that metabolize DNA, mainly due to the inherent inaccessibility of the DNA template. Despite extensive understanding of the involvement of chromatin-modifying factors in transcription, roles of related activities in DNA replication remain largely elusive. Here, we show that the heterodimeric transcriptional elongation factor FACT (facilitates chromatin transcription) is functionally linked to DNA synthesis. Its involvement in DNA replication is partly mediated by the stable association with the replicative helicase complex, MCM, and further by the coexistence with MCM on replication origin. Furthermore, relying on its nucleosome-reorganizing activity, FACT can facilitate chromatin unwinding by the MCM complex, which is otherwise inert on the nucleosomal template. As a consequence, the physical and functional interaction between FACT and MCM is an important determinant in the proper initiation of DNA replication and S phase in vivo. Together, our findings identify FACT as an integral and conserved component of the endogenous replication machinery, and support a model in which the concerted action of helicase and chromatin-modifying activities promotes chromosome replication.
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Affiliation(s)
| | | | - Susumu Hirose
- Department of Developmental Genetics, National Institute of Genetics, Mishima, Shizuokaken, Japan
| | - Sheng-Chung Lee
- Institute of Molecular Medicine, National Taiwan University, Taipei, Taiwan
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
- Institute of Molecular Medicine, National Taiwan University, 7 Chung Shan South Road, Taipei, Taiwan. Tel.: +886 2 2356 2982; Fax: +886 2 2395 7801; E-mail:
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31
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Tsuji T, Ficarro SB, Jiang W. Essential role of phosphorylation of MCM2 by Cdc7/Dbf4 in the initiation of DNA replication in mammalian cells. Mol Biol Cell 2006; 17:4459-72. [PMID: 16899510 PMCID: PMC1635350 DOI: 10.1091/mbc.e06-03-0241] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
We report the identification of Cdc7/Dbf4 phosphorylation sites in human MCM2 and the determination of the role of Cdc7/Dbf4 phosphorylation of MCM2 in the initiation of DNA replication. Using immunoblotting, immunofluorescence, and high-speed automated cell-imaging analyses with antibodies specific against MCM2 and Cdc7/Dbf4 phosphorylated MCM2, we show that the chromatin recruitment and phosphorylation of MCM2 are regulated during the cell cycle in HeLa cells. Chromatin-bound MCM2 is phosphorylated by Cdc7/Dbf4 during G1/S, which coincides with the initiation of DNA replication. Moreover, we show that baculovirus-expressed purified MCM2-7 complex and its phosphomimetic MCM2E-7 complex display higher ATPase activity when compared with the nonphosphorylatable MCM2A-7 complex in vitro. Furthermore, suppression of MCM2 expression in HeLa cells by siRNA results in the inhibition of DNA replication. The inhibition can be rescued by the coexpression of wild type MCM2 or MCM2E but not MCM2A. Taken together, these results indicate that Cdc7/Dbf4 phosphorylation of MCM2 is essential for the initiation of DNA replication in mammalian cells.
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Affiliation(s)
- Toshiya Tsuji
- *The Burnham Institute for Medical Research, La Jolla, CA 92037; and
| | - Scott B. Ficarro
- Genomics Institute of the Novartis Research Foundation, San Diego, CA 92121
| | - Wei Jiang
- *The Burnham Institute for Medical Research, La Jolla, CA 92037; and
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32
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Shin JH, Kelman Z. The replicative helicases of bacteria, archaea, and eukarya can unwind RNA-DNA hybrid substrates. J Biol Chem 2006; 281:26914-21. [PMID: 16829518 DOI: 10.1074/jbc.m605518200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Replicative helicases are hexameric enzymes that unwind DNA during chromosomal replication. They use energy from nucleoside triphosphate hydrolysis to translocate along one strand of the duplex DNA and displace the complementary strand. Here, the ability of a replicative helicase from each of the three domains, bacteria, archaea, and eukarya, to unwind RNA-containing substrate was determined. It is shown that all three helicases can unwind DNA-RNA hybrids while translocating along the single-stranded DNA. No unwinding could be observed when the helicases were provided with a single-stranded RNA overhang. Using DNA, RNA, and DNA-RNA chimeric oligonucleotides it was found that whereas the enzymes can bind both DNA and RNA, they could translocate only along DNA and only DNA stimulates the ATPase activity of the enzymes. Recent observations suggest that helicases may interact with enzymes participating in RNA metabolism and that RNA-DNA hybrids may be present on the chromosomes. Thus, the results presented here may suggest a new role for the replicative helicases during chromosomal replication or in other cellular processes.
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Affiliation(s)
- Jae-Ho Shin
- University of Maryland Biotechnology Institute, Center for Advanced Research in Biotechnology, Rockville, Maryland 20850, USA
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33
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Moyer SE, Lewis PW, Botchan MR. Isolation of the Cdc45/Mcm2-7/GINS (CMG) complex, a candidate for the eukaryotic DNA replication fork helicase. Proc Natl Acad Sci U S A 2006; 103:10236-10241. [PMID: 16798881 PMCID: PMC1482467 DOI: 10.1073/pnas.0602400103] [Citation(s) in RCA: 523] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The protein Cdc45 plays a critical but poorly understood role in the initiation and elongation stages of eukaryotic DNA replication. To study Cdc45's function in DNA replication, we purified Cdc45 protein from Drosophila embryo extracts by a combination of traditional and immunoaffinity chromatography steps and found that the protein exists in a stable, high-molecular-weight complex with the Mcm2-7 hexamer and the GINS tetramer. The purified Cdc45/Mcm2-7/GINS complex is associated with an active ATP-dependent DNA helicase function. RNA interference knock-down experiments targeting the GINS and Cdc45 components establish that the proteins are required for the S phase transition in Drosophila cells. The data suggest that this complex forms the core helicase machinery for eukaryotic DNA replication.
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Affiliation(s)
- Stephen E Moyer
- Department of Molecular and Cell Biology, Division of Biochemistry and Molecular Biology, University of California, Berkeley, CA 94720
| | - Peter W Lewis
- Department of Molecular and Cell Biology, Division of Biochemistry and Molecular Biology, University of California, Berkeley, CA 94720
| | - Michael R Botchan
- Department of Molecular and Cell Biology, Division of Biochemistry and Molecular Biology, University of California, Berkeley, CA 94720
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Komamura-Kohno Y, Karasawa-Shimizu K, Saitoh T, Sato M, Hanaoka F, Tanaka S, Ishimi Y. Site-specific phosphorylation of MCM4 during the cell cycle in mammalian cells. FEBS J 2006; 273:1224-39. [PMID: 16519687 DOI: 10.1111/j.1742-4658.2006.05146.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
MCM4, a subunit of a putative replicative helicase, is phosphorylated during the cell cycle, at least in part by cyclin-dependent kinases (CDK), which play a central role in the regulation of DNA replication. However, detailed characterization of the phosphorylation of MCM4 remains to be performed. We examined the phosphorylation of human MCM4 at Ser3, Thr7, Thr19, Ser32, Ser54, Ser88 and Thr110 using anti-phosphoMCM4 sera. Western blot analysis of HeLa cells indicated that phosphorylation of MCM4 at these seven sites can be classified into two groups: (a) phosphorylation that is greatly enhanced in the G2 and M phases (Thr7, Thr19, Ser32, Ser54, Ser88 and Thr110), and (b) phosphorylation that is firmly detected during interphase (Ser3). We present data indicating that phosphorylation at Thr7, Thr19, Ser32, Ser88 and Thr110 in the M phase requires CDK1, using a temperature-sensitive mutant of mouse CDK1, and phosphorylation at sites 3 and 32 during interphase requires CDK2, using a dominant-negative mutant of human CDK2. Based on these results and those from in vitro phosphorylation of MCM4 with CDK2/cyclin A, we discuss the kinases responsible for MCM4 phosphorylation. Phosphorylated MCM4 detected using anti-phospho sera exhibited different affinities for chromatin. Studies on the nuclear localization of chromatin-bound MCM4 phosphorylated at sites 3 and 32 suggested that they are not generally colocalized with replicating DNA. Unexpectedly, MCM4 phosphorylated at site 32 was enriched in the nucleolus through the cell cycle. These results suggest that phosphorylation of MCM4 has several distinct and site-specific roles in the function of MCM during the mammalian cell cycle.
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Costa A, Pape T, van Heel M, Brick P, Patwardhan A, Onesti S. Structural studies of the archaeal MCM complex in different functional states. J Struct Biol 2006; 156:210-9. [PMID: 16731005 DOI: 10.1016/j.jsb.2006.04.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2005] [Revised: 03/31/2006] [Accepted: 04/03/2006] [Indexed: 10/24/2022]
Abstract
The primary candidate for the eukaryotic replicative helicase is the MCM2-7 complex, a hetero-oligomer formed by six AAA+ paralogous polypeptides. A simplified model for structure-function studies is the homo-oligomeric orthologue from the archaeon Methanothermobacter thermoautotrophicus. The crystal structure of the DNA-interacting N-terminal domain of this homo-oligomer revealed a double hexamer in a head-to-head configuration; single-particle electron microscopy studies have shown that the full-length protein complex can form both single and double rings, in which each ring can consist of a cyclical arrangement of six or seven subunits. Using single-particle techniques and especially multivariate statistical symmetry analysis, we have assessed the changes in stoichiometry that the complex undergoes when treated with various nucleotide analogues or when binding a double-stranded DNA fragment. We found that the binding of nucleotides or of double-stranded DNA leads to the preferred formation of double-ring structures. Specifically, the protein complex is present as a double heptamer when treated with a nucleotide analogue, but it is rather found as a double hexamer when complexed with double-stranded DNA. The possible physiological role of the various stoichiometries of the complex is discussed in the light of the proposed mechanisms of helicase activity.
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Affiliation(s)
- Alessandro Costa
- Division of Cell and Molecular Biology, Imperial College London SW7 2AZ, UK
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Ryu MJ, Kim BJ, Lee JW, Lee MW, Choi HK, Kim ST. Direct interaction between cohesin complex and DNA replication machinery. Biochem Biophys Res Commun 2006; 341:770-5. [PMID: 16438930 DOI: 10.1016/j.bbrc.2006.01.029] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2006] [Accepted: 01/10/2006] [Indexed: 11/30/2022]
Abstract
Structural maintenance of chromosome 1 (Smc1) is a multifunctional protein, which has been implicated in sister chromatid cohesion, DNA recombination and repair, and the activation of cell cycle checkpoints by ionizing radiation, ultraviolet light, and other genotoxic agents. In order to identify the proteins that interact with Smc1, we conducted the Tandem affinity purification (TAP) technique and analyzed the Smc1-interacting proteins via MALDI-TOF mass spectrometry. We identified minichromosome maintenance 7 (Mcm7), an essential component of the pre-replication complex, as a novel Smc1-interacting protein. Co-immunoprecipitation revealed an interaction occurring between Smc1 and Mcm7, both in vitro and in vivo. Using a GST pull-down assay, we determined that Smc1 interacts physically with Mcm7 via its N-terminal and hinge regions, and Mcm7 interacts with Smc1 via its middle region. Interestingly, we also discovered that Smc1 interacts with other DNA replication proteins, including Mcm6, RFC1, and DNA polymerase alpha. These results suggest that a functional link exists between the cohesin complex and DNA replication proteins.
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Affiliation(s)
- Min-Jung Ryu
- Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, 300 Chonchon-Dong, Suwon, Kyunggi-Do 440-746, Republic of Korea
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Kowalczyk L, Rajewska M, Konieczny I. Positioning and the specific sequence of each 13-mer motif are critical for activity of the plasmid RK2 replication origin. Mol Microbiol 2005; 57:1439-49. [PMID: 16102011 DOI: 10.1111/j.1365-2958.2005.04770.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The minimal replication origin of the broad-host-range plasmid RK2, oriV, contains five iterons which are binding sites for the plasmid-encoded replication initiation protein TrfA, four DnaA boxes, which bind the host DnaA protein, and an AT-rich region containing four 13-mer sequences. In this study, 26 mutants with altered sequence and/or spacing of 13-mer motifs have been constructed and analysed for replication activity in vivo and in vitro. The data show that the replacement of oriV 13-mers by similar but not identical 13-mer sequences from Escherichia coli oriC inactivates the origin. In addition, interchanging the positions of the oriV 13-mers results in greatly reduced activity. Mutants with T/A substitutions are also inactive. Furthermore, introduction of single-nucleotide substitutions demonstrates very restricted sequence requirements depending on the 13-mer position. Only two of the mutants are host specific, functional in Pseudomonas aeruginosa but not in E. coli. Our experiments demonstrate considerable complexity in the plasmid AT-rich region architecture required for functionality. It is evident that low internal stability of this region is not the only feature contributing to origin activity. Our studies suggest a requirement for sequence-specific protein interactions within the 13-mers during assembly of replication complexes at the plasmid origin.
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Affiliation(s)
- Lukasz Kowalczyk
- Department of Molecular and Cellular Biology, Intercollegiate Faculty of Biotechnology, University of Gdansk, ul. Kladki 24, 80-822 Gdansk, Poland
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Masai H, You Z, Arai KI. Control of DNA replication: regulation and activation of eukaryotic replicative helicase, MCM. IUBMB Life 2005; 57:323-35. [PMID: 16036617 DOI: 10.1080/15216540500092419] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
DNA replication is a key event of cell proliferation and the final target of signal transduction induced by growth factor stimulation. It is also strictly regulated during the ongoing cell cycle so that it occurs only once during S phase and that all the genetic materials are faithfully duplicated. DNA replication may be arrested or temporally inhibited due to a varieties of internal and external causes. Cells have developed intricate mechanisms to cope with the arrested replication forks to minimize the adversary effect on the stable maintenance of genetic materials. Helicases play a central role in DNA replication. In eukaryotes, MCM (minichromosome maintenance) protein complex plays essential roles as a replicative helicase. MCM4-6-7 complex possesses intrinsic DNA helicase activity which translocates on single-stranded DNA form 3' to 5'. Mammalian MCM4-6-7 helicase and ATPase activities are specifically stimulated by the presence of thymine-rich single-stranded DNA sequences onto which it is loaded. The activation appears to depend on the thymine content of this single-strand, and sequences derived from human replication origins can serve as potent activators of the MCM helicase. MCM is a prime target of Cdc7 kinase, known to be essential for activation of replication origins. We will discuss how the MCM may be activated at the replication origins by template DNA, phosphorylation, and interaction with other replicative proteins, and will present a model of how activation of MCM helicase by specific sequences may contribute to selection of replication initiation sites in higher eukaryotes.
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Affiliation(s)
- Hisao Masai
- Department of Cell Biology, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
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Abstract
Helicases play central roles in initiation and elongation of DNA replication. We previously reported that helicase and ATPase activities of the mammalian Mcm4/6/7 complex are activated specifically by thymine-rich single-stranded DNA. Here, we examined its substrate preference and helicase actions using various synthetic DNAs. On a bubble substrate, Mcm4/6/7 makes symmetric dual contacts with the 5′-proximal 25 nt single-stranded segments adjacent to the branch points, presumably generating double hexamers. Loss of thymine residues from one single-strand results in significant decrease of unwinding efficacy, suggesting that concurrent bidirectional unwinding by a single double hexameric Mcm4/6/7 may play a role in efficient unwinding of the bubble. Mcm4/6/7 binds and unwinds various fork and extension structures carrying a single-stranded 3′-tail DNA. The extent of helicase activation depends on the sequence context of the 3′-tail, and the maximum level is achieved by DNA with 50% or more thymine content. Strand displacement by Mcm4/6/7 is inhibited, as the GC content of the duplex region increases. Replacement of cytosine–guanine pairs with cytosine–inosine pairs in the duplex restored unwinding, suggesting that mammalian Mcm4/6/7 helicase has difficulties in unwinding stably base-paired duplex. Taken together, these findings reveal important features on activation and substrate preference of the eukaryotic replicative helicase.
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Affiliation(s)
| | - Hisao Masai
- To whom correspondence should be addressed. Tel: +81 3 5685 2264; Fax: +81 3 5685 2932;
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40
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Aladjem MI, Fanning E. The replicon revisited: an old model learns new tricks in metazoan chromosomes. EMBO Rep 2005; 5:686-91. [PMID: 15229645 PMCID: PMC1299096 DOI: 10.1038/sj.embor.7400185] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2004] [Accepted: 05/12/2004] [Indexed: 01/09/2023] Open
Abstract
The origins of DNA replication were proposed in the replicon model to be specified genetically by replicator elements that coordinate the initiation of DNA synthesis with gene expression and cell growth. Recent studies have identified DNA sequences in mammalian cells that fulfil the genetic criteria for replicators and are beginning to uncover the sequence requirements for the initiation of DNA replication. Mammalian replicators are com- posed of non-redundant modules that cooperate to direct initiation to specific chromosomal sites. Conversely, replicators do not show strong sequence similarity, and their ability to initiate replication depends on the chromosomal context and epigenetic factors, as well as their primary sequence. Here, we review the properties of metazoan replicators, and discuss the genetic and epigenetic factors that determine where and when DNA replication is initiated.
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Affiliation(s)
- Mirit I. Aladjem
- Laboratory of Molecular Pharmacology, DSB, National Cancer Institute, National Institutes of Health, Building 37, Room 5056, 37 Convent Drive, Bethesda, Maryland 20892-4255, USA
- Tel: +1 301 435 4255; Fax: +1 301 402 9752;
| | - Ellen Fanning
- Department of Biological Sciences and Vanderbilt–Ingram Cancer Center, Vanderbilt University Station B-351634, Vanderbilt University, Nashville, Tennessee 327232-1634, USA
- Tel: +1 615 343 5677; Fax: +1 615 343 6707;
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Kemp MG, Ghosh M, Liu G, Leffak M. The histone deacetylase inhibitor trichostatin A alters the pattern of DNA replication origin activity in human cells. Nucleic Acids Res 2005; 33:325-36. [PMID: 15653633 PMCID: PMC546162 DOI: 10.1093/nar/gki177] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Eukaryotic chromatin structure limits the initiation of DNA replication spatially to chromosomal origin zones and temporally to the ordered firing of origins during S phase. Here, we show that the level of histone H4 acetylation correlates with the frequency of replication initiation as measured by the abundance of short nascent DNA strands within the human c-myc and lamin B2 origins, but less well with the frequency of initiation across the β-globin locus. Treatment of HeLa cells with trichostatin A (TSA) reversibly increased the acetylation level of histone H4 globally and at these initiation sites. At all three origins, TSA treatment transiently promoted a more dispersive pattern of initiations, decreasing the abundance of nascent DNA at previously preferred initiation sites while increasing the nascent strand abundance at lower frequency genomic initiation sites. When cells arrested in late G1 were released into TSA, they completed S phase more rapidly than untreated cells, possibly due to the earlier initiation from late-firing origins, as exemplified by the β-globin origin. Thus, TSA may modulate replication origin activity through its effects on chromatin structure, by changing the selection of initiation sites, and by advancing the time at which DNA synthesis can begin at some initiation sites.
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Affiliation(s)
| | | | | | - Michael Leffak
- To whom correspondence should be addressed. Tel: +1 937 775 3125; Fax: +1 937 775 3730;
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De Falco M, Fusco A, De Felice M, Rossi M, Pisani FM. The DNA primase of Sulfolobus solfataricus is activated by substrates containing a thymine-rich bubble and has a 3'-terminal nucleotidyl-transferase activity. Nucleic Acids Res 2004; 32:5223-30. [PMID: 15459292 PMCID: PMC521673 DOI: 10.1093/nar/gkh865] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
DNA primases are responsible for the synthesis of the short RNA primers that are used by the replicative DNA polymerases to initiate DNA synthesis on the leading- and lagging-strand at the replication fork. In this study, we report the purification and biochemical characterization of a DNA primase (Sso DNA primase) from the thermoacidophilic crenarchaeon Sulfolobus solfataricus. The Sso DNA primase is a heterodimer composed of two subunits of 36 kDa (small subunit) and 38 kDa (large subunit), which show sequence similarity to the eukaryotic DNA primase p60 and p50 subunits, respectively. The two polypeptides were co-expressed in Escherichia coli and purified as a heterodimeric complex, with a Stokes radius of about 39.2 A and a 1:1 stoichiometric ratio among its subunits. The Sso DNA primase utilizes poly-pyrimidine single-stranded DNA templates with low efficiency for de novo synthesis of RNA primers, whereas its synthetic function is specifically activated by thymine-containing synthetic bubble structures that mimic early replication intermediates. Interestingly, the Sso DNA primase complex is endowed with a terminal nucleotidyl-transferase activity, being able to incorporate nucleotides at the 3' end of synthetic oligonucleotides in a non-templated manner.
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Affiliation(s)
- Mariarosaria De Falco
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via P. Castellino, 111, 80131-Napoli, Italy
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Pucci B, De Felice M, Rossi M, Onesti S, Pisani FM. Amino acids of the Sulfolobus solfataricus mini-chromosome maintenance-like DNA helicase involved in DNA binding/remodeling. J Biol Chem 2004; 279:49222-8. [PMID: 15371413 DOI: 10.1074/jbc.m408967200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Herein we report the identification of amino acids of the Sulfolobus solfataricus mini-chromosome maintenance (MCM)-like DNA helicase (SsoMCM), which are critical for DNA binding/remodeling. The crystallographic structure of the N-terminal portion (residues 2-286) of the Methanothermobacter thermoautotrophicum MCM protein revealed a dodecameric assembly with two hexameric rings in a head-to-head configuration and a positively charged central channel proposed to encircle DNA molecules. A structure-guided alignment of the M. thermoautotrophicum and S. solfataricus MCM sequences identified positively charged amino acids in SsoMCM that could point to the center of the channel. These residues (Lys-129, Lys-134, His-146, and Lys-194) were changed to alanine. The purified mutant proteins were all found to form homo-hexamers in solution and to retain full ATPase activity. K129A, H146A, and K194A SsoMCMs are unable to bind DNA either in single- or double-stranded form in band shift assays and do not display helicase activity. In contrast, the substitution of lysine 134 to alanine affects only binding to duplex DNA molecules, whereas it has no effect on binding to single-stranded DNA and on the DNA unwinding activity. These results have important implications for the understanding of the molecular mechanism of the MCM DNA helicase action.
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Affiliation(s)
- Biagio Pucci
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via P. Castellino 111, 80131 Napoli, Italy
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