1
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Gul H, Selvi S, Yilmaz F, Ozcelik G, Olfaz‐Aslan S, Yazan S, Tiryaki B, Gul S, Yurtseven A, Kavakli IH, Ozlu N, Ozturk N. Proteome analysis of the circadian clock protein PERIOD2. Proteins 2022; 90:1315-1330. [DOI: 10.1002/prot.26314] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 01/25/2022] [Accepted: 01/29/2022] [Indexed: 12/17/2022]
Affiliation(s)
- Huseyin Gul
- Department of Molecular Biology and Genetics Gebze Technical University Gebze Kocaeli Turkey
| | - Saba Selvi
- Department of Molecular Biology and Genetics Gebze Technical University Gebze Kocaeli Turkey
| | - Fatma Yilmaz
- Department of Molecular Biology and Genetics Gebze Technical University Gebze Kocaeli Turkey
| | - Gozde Ozcelik
- Department of Molecular Biology and Genetics Gebze Technical University Gebze Kocaeli Turkey
| | - Senanur Olfaz‐Aslan
- Department of Molecular Biology and Genetics Gebze Technical University Gebze Kocaeli Turkey
| | - Seyma Yazan
- Department of Molecular Biology and Genetics Gebze Technical University Gebze Kocaeli Turkey
| | - Busra Tiryaki
- Department of Molecular Biology and Genetics Gebze Technical University Gebze Kocaeli Turkey
| | - Seref Gul
- Department of Biology Istanbul University Istanbul Turkey
| | - Ali Yurtseven
- Department of Molecular Biology and Genetics Koc University Istanbul Turkey
| | - Ibrahim Halil Kavakli
- Department of Molecular Biology and Genetics Koc University Istanbul Turkey
- Department of Chemical and Biological Engineering Koc University Istanbul Turkey
| | - Nurhan Ozlu
- Department of Molecular Biology and Genetics Koc University Istanbul Turkey
| | - Nuri Ozturk
- Department of Molecular Biology and Genetics Gebze Technical University Gebze Kocaeli Turkey
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2
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Stepchenkova EI, Zhuk AS, Cui J, Tarakhovskaya ER, Barbari SR, Shcherbakova PV, Polev DE, Fedorov R, Poliakov E, Rogozin IB, Lada AG, Pavlov YI. Compensation for the absence of the catalytically active half of DNA polymerase ε in yeast by positively selected mutations in CDC28. Genetics 2021; 218:6222163. [PMID: 33844024 DOI: 10.1093/genetics/iyab060] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 04/02/2021] [Indexed: 11/14/2022] Open
Abstract
Current eukaryotic replication models postulate that leading and lagging DNA strands are replicated predominantly by dedicated DNA polymerases. The catalytic subunit of the leading strand DNA polymerase ε, Pol2, consists of two halves made of two different ancestral B-family DNA polymerases. Counterintuitively, the catalytically active N-terminal half is dispensable, while the inactive C-terminal part is required for viability. Despite extensive studies of yeast Saccharomyces cerevisiae strains lacking the active N-terminal half, it is still unclear how these strains survive and recover. We designed a robust method for constructing mutants with only the C-terminal part of Pol2. Strains without the active polymerase part show severe growth defects, sensitivity to replication inhibitors, chromosomal instability, and elevated spontaneous mutagenesis. Intriguingly, the slow-growing mutant strains rapidly accumulate fast-growing clones. Analysis of genomic DNA sequences of these clones revealed that the adaptation to the loss of the catalytic N-terminal part of Pol2 occurs by a positive selection of mutants with improved growth. Elevated mutation rates help generate sufficient numbers of these variants. Single nucleotide changes in the cell cycle-dependent kinase gene, CDC28, improve the growth of strains lacking the N-terminal part of Pol2, and rescue their sensitivity to replication inhibitors and, in parallel, lower mutation rates. Our study predicts that changes in mammalian homologs of cyclin-dependent kinases may contribute to cellular responses to the leading strand polymerase defects.
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Affiliation(s)
- Elena I Stepchenkova
- Laboratory of Mutagenesis and Genetic Toxicology, Vavilov Institute of General Genetics, Saint-Petersburg Branch, Russian Academy of Sciences, Saint-Petersburg 199034, Russia.,Department of Genetics and Biotechnology, Saint-Petersburg State University, Saint-Petersburg 199034, Russia.,Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Anna S Zhuk
- ITMO University, Saint-Petersburg 191002, Russia
| | - Jian Cui
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Elena R Tarakhovskaya
- Laboratory of Mutagenesis and Genetic Toxicology, Vavilov Institute of General Genetics, Saint-Petersburg Branch, Russian Academy of Sciences, Saint-Petersburg 199034, Russia.,Department of Plant Physiology and Biochemistry, Saint-Petersburg State University, Saint-Petersburg 199034, Russia
| | - Stephanie R Barbari
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Polina V Shcherbakova
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Dmitrii E Polev
- Research Resource Center "Biobank," Research Park, Saint-Petersburg State University, Saint-Petersburg 198504, Russia
| | - Roman Fedorov
- Department of Mathematics, University of Pittsburgh, PA 15213, USA
| | - Eugenia Poliakov
- Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Igor B Rogozin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Artem G Lada
- Department of Microbiology and Molecular Genetics, University of California Davis, Davis, CA 92697, USA
| | - Youri I Pavlov
- Department of Genetics and Biotechnology, Saint-Petersburg State University, Saint-Petersburg 199034, Russia.,Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA.,Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198, USA.,Department of Microbiology and Pathology, University of Nebraska Medical Center, Omaha, NE 68198, USA.,Department of Genetics Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE 68198, USA
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3
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Kobaisi F, Fayyad N, Sulpice E, Badran B, Fayyad-Kazan H, Rachidi W, Gidrol X. High-throughput synthetic rescue for exhaustive characterization of suppressor mutations in human genes. Cell Mol Life Sci 2020; 77:4209-4222. [PMID: 32270227 PMCID: PMC7588364 DOI: 10.1007/s00018-020-03519-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 03/21/2020] [Accepted: 03/30/2020] [Indexed: 02/06/2023]
Abstract
Inherited or acquired mutations can lead to pathological outcomes. However, in a process defined as synthetic rescue, phenotypic outcome created by primary mutation is alleviated by suppressor mutations. An exhaustive characterization of these mutations in humans is extremely valuable to better comprehend why patients carrying the same detrimental mutation exhibit different pathological outcomes or different responses to treatment. Here, we first review all known suppressor mutations' mechanisms characterized by genetic screens on model species like yeast or flies. However, human suppressor mutations are scarce, despite some being discovered based on orthologue genes. Because of recent advances in high-throughput screening, developing an inventory of human suppressor mutations for pathological processes seems achievable. In addition, we review several screening methods for suppressor mutations in cultured human cells through knock-out, knock-down or random mutagenesis screens on large scale. We provide examples of studies published over the past years that opened new therapeutic avenues, particularly in oncology.
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Affiliation(s)
- Farah Kobaisi
- University of Grenoble Alpes, CEA, INSERM, IRIG-BGE U1038, 38000, Grenoble, France
- Laboratory of Cancer Biology and Molecular Immunology, Faculty of Sciences I, Lebanese University, Hadath, Lebanon
- University of Grenoble Alpes, SYMMES/CIBEST UMR 5819 UGA-CNRS-CEA, IRIG/CEA-Grenoble, Grenoble, France
| | - Nour Fayyad
- University of Grenoble Alpes, SYMMES/CIBEST UMR 5819 UGA-CNRS-CEA, IRIG/CEA-Grenoble, Grenoble, France
| | - Eric Sulpice
- University of Grenoble Alpes, CEA, INSERM, IRIG-BGE U1038, 38000, Grenoble, France
| | - Bassam Badran
- Laboratory of Cancer Biology and Molecular Immunology, Faculty of Sciences I, Lebanese University, Hadath, Lebanon
| | - Hussein Fayyad-Kazan
- Laboratory of Cancer Biology and Molecular Immunology, Faculty of Sciences I, Lebanese University, Hadath, Lebanon
| | - Walid Rachidi
- University of Grenoble Alpes, SYMMES/CIBEST UMR 5819 UGA-CNRS-CEA, IRIG/CEA-Grenoble, Grenoble, France
| | - Xavier Gidrol
- University of Grenoble Alpes, CEA, INSERM, IRIG-BGE U1038, 38000, Grenoble, France.
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4
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Abstract
Replicative DNA helicases are essential cellular enzymes that unwind duplex DNA in front of the replication fork during chromosomal DNA replication. Replicative helicases were discovered, beginning in the 1970s, in bacteria, bacteriophages, viruses, and eukarya, and, in the mid-1990s, in archaea. This year marks the 20th anniversary of the first report on the archaeal replicative helicase, the minichromosome maintenance (MCM) protein. This minireview summarizes 2 decades of work on the archaeal MCM.
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5
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Shimozaki K. Ten-Eleven Translocation 1 and 2 Confer Overlapping Transcriptional Programs for the Proliferation of Cultured Adult Neural Stem Cells. Cell Mol Neurobiol 2016; 37:995-1008. [PMID: 27778125 DOI: 10.1007/s10571-016-0432-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 10/13/2016] [Indexed: 11/24/2022]
Abstract
Adult neurogenesis originates from neural stem cells (NSCs) in specific regions of the adult brain. The molecular mechanisms that control the self-renewal and multipotency of NSCs have not been fully elucidated. In recent years, emerging evidence has revealed that ten-eleven translocation (TET) family DNA dioxygenases TET1 and TET2 play important roles in the central nervous system. Here, I present evidence that Tet1 and Tet2 are expressed in cultured NSCs derived from adult mouse brain and play an important role in the proliferative self-renewal of NSCs in an undifferentiated state. The investigation of intracellular molecular networks involving both Tet1 and Tet2 by gene knockdown and comprehensive genetic analyses showed that overlapping molecular mechanisms involving TET1 and TET2 regulate the expression of at least 16 genes required for DNA replication and cell cycle control. Interestingly, transcriptional regulation of the selected gene through TET1 and TET2 did not correlate with direct CpG demethylation of the gene promoter. These findings suggest that TET1 and TET2 play an important role in the proliferation of NSCs in the adult mouse brain by specifically regulating common genes for DNA replication and the cell cycle.
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Affiliation(s)
- Koji Shimozaki
- Division of Functional Genomics, Life Science Support Center, Nagasaki University, Nagasaki, 852-8523, Japan.
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6
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Nowinska K, Chmielewska M, Piotrowska A, Pula B, Pastuszewski W, Krecicki T, Podhorska-Okołow M, Zabel M, Dziegiel P. Correlation between levels of expression of minichromosome maintenance proteins, Ki-67 proliferation antigen and metallothionein I/II in laryngeal squamous cell cancer. Int J Oncol 2015; 48:635-45. [PMID: 26648405 DOI: 10.3892/ijo.2015.3273] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 10/27/2015] [Indexed: 11/06/2022] Open
Abstract
MCM2, MCM3 and MCM7 are minichromosome maintenance proteins found in dividing cells and they play a role in DNA synthesis. Increased MCM expression level is observed in cells of different cancer types. Additionally, metallothioneins (MT-I/II) are involved in control of cell proliferation and differentiation and changes of their expression are observed in many types of cancer. Ki-67 is known cancer cell proliferation antigen currently used in prognostic evaluation. The study material consisted of 83 laryngeal squamous cell cancer (LSCC) cases and 10 benign hypertrophic lesions of larynx epithelium as a control group. For the present study, laryngeal cancer cell line HEp-2 and human keratinocytes were employed, and to evaluate expression of all the markers, immunohistochemical method (IHC), immunofluorescence (IF) and western blot analysis were used. Statistical analysis showed strong positive correlation between expression of MCM2, MCM3, MCM7 and Ki-67 antigen in LSCC. Additionally, moderate positive correlation was observed between MCM3 and MT-I/II expression. In cancer cells, the level of expression of MCM3, MCM2, MCM7 and Ki-67 markers was increasing with the grade of LSCC malignancy. IF and western blot analysis showed higher MCM2, MCM3, MCM7 expression in HEp-2 cells in comparison to their expression in keratinocytes. MCM proteins might be useful markers of cell proliferation in LSCC.
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Affiliation(s)
- Katarzyna Nowinska
- Department of Histology and Embryology, Wroclaw Medical University, Wroclaw, Poland
| | | | | | - Bartosz Pula
- Department of Histology and Embryology, Wroclaw Medical University, Wroclaw, Poland
| | | | - Tomasz Krecicki
- Department of Otolaryngology, Head and Neck Surgery, Wroclaw Medical University, Wroclaw, Poland
| | | | - Maciej Zabel
- Department of Histology and Embryology, Wroclaw Medical University, Wroclaw, Poland
| | - Piotr Dziegiel
- Department of Histology and Embryology, Wroclaw Medical University, Wroclaw, Poland
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7
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Han X, Mayca Pozo F, Wisotsky JN, Wang B, Jacobberger JW, Zhang Y. Phosphorylation of Minichromosome Maintenance 3 (MCM3) by Checkpoint Kinase 1 (Chk1) Negatively Regulates DNA Replication and Checkpoint Activation. J Biol Chem 2015; 290:12370-8. [PMID: 25809478 DOI: 10.1074/jbc.m114.621532] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Indexed: 01/08/2023] Open
Abstract
Mechanisms controlling DNA replication and replication checkpoint are critical for the maintenance of genome stability and the prevention or treatment of human cancers. Checkpoint kinase 1 (Chk1) is a key effector protein kinase that regulates the DNA damage response and replication checkpoint. The heterohexameric minichromosome maintenance (MCM) complex is the core component of mammalian DNA helicase and has been implicated in replication checkpoint activation. Here we report that Chk1 phosphorylates the MCM3 subunit of the MCM complex at Ser-205 under normal growth conditions. Mutating the Ser-205 of MCM3 to Ala increased the length of DNA replication track and shortened the S phase duration, indicating that Ser-205 phosphorylation negatively controls normal DNA replication. Upon replicative stress treatment, the inhibitory phosphorylation of MCM3 at Ser-205 was reduced, and this reduction was accompanied with the generation of single strand DNA, the key platform for ataxia telangiectasia mutated and Rad3-related (ATR) activation. As a result, the replication checkpoint is activated. Together, these data provide significant insights into the regulation of both normal DNA replication and replication checkpoint activation through the novel phosphorylation of MCM3 by Chk1.
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Affiliation(s)
| | | | | | | | - James W Jacobberger
- Division of General Medical Sciences, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106 Case Comprehensive Cancer Center
| | - Youwei Zhang
- From the Departments of Pharmacology and Case Comprehensive Cancer Center, Genetics and Genome Science,
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8
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Han X, Aslanian A, Fu K, Tsuji T, Zhang Y. The interaction between checkpoint kinase 1 (Chk1) and the minichromosome maintenance (MCM) complex is required for DNA damage-induced Chk1 phosphorylation. J Biol Chem 2014; 289:24716-23. [PMID: 25049228 DOI: 10.1074/jbc.m114.575035] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Chk1 is an essential mediator of the DNA damage response and cell cycle checkpoint. However, how exactly Chk1 transduces the checkpoint signaling is not fully understood. Here we report the identification of the heterohexamic minichromosome maintenance (MCM) complex that interacts with Chk1 by mass spectrometry. The interaction between Chk1 and the MCM complex was reduced by DNA damage treatment. We show that the MCM complex, at least partially, contributes to the chromatin association of Chk1, allowing for immediate phosphorylation of Chk1 by ataxia telangiectasia mutated and Rad3-related (ATR) in the presence of DNA damage. Further, phosphorylation of Chk1 at ATR sites reduces the interaction between Chk1 and the MCM complex, facilitating chromatin release of phosphorylated Chk1, a critical step in the initiation and amplification of cell cycle checkpoint. Together, these data provide novel insights into the activation of Chk1 in response to DNA damage.
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Affiliation(s)
- Xiangzi Han
- From the Department of Pharmacology, Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, Ohio 44106
| | - Aaron Aslanian
- the Molecular and Cellular Biology Laboratories, The Salk Institute, La Jolla, California 92037, and
| | - Kang Fu
- From the Department of Pharmacology, Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, Ohio 44106
| | | | - Youwei Zhang
- From the Department of Pharmacology, Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, Ohio 44106,
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9
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Lam SKW, Ma X, Sing TL, Shilton BH, Brandl CJ, Davey MJ. The PS1 hairpin of Mcm3 is essential for viability and for DNA unwinding in vitro. PLoS One 2013; 8:e82177. [PMID: 24349215 PMCID: PMC3859580 DOI: 10.1371/journal.pone.0082177] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 10/21/2013] [Indexed: 11/19/2022] Open
Abstract
The pre-sensor 1 (PS1) hairpin is found in ring-shaped helicases of the AAA+ family (ATPases associated with a variety of cellular activities) of proteins and is implicated in DNA translocation during DNA unwinding of archaeal mini-chromosome maintenance (MCM) and superfamily 3 viral replicative helicases. To determine whether the PS1 hairpin is required for the function of the eukaryotic replicative helicase, Mcm2-7 (also comprised of AAA+ proteins), we mutated the conserved lysine residue in the putative PS1 hairpin motif in each of the Saccharomyces cerevisiae Mcm2-7 subunits to alanine. Interestingly, only the PS1 hairpin of Mcm3 was essential for viability. While mutation of the PS1 hairpin in the remaining MCM subunits resulted in minimal phenotypes, with the exception of Mcm7 which showed slow growth under all conditions examined, the viable alleles were synthetic lethal with each other. Reconstituted Mcm2-7 containing Mcm3 with the PS1 mutation (Mcm3(K499A)) had severely decreased helicase activity. The lack of helicase activity provides a probable explanation for the inviability of the mcm3(K499A) strain. The ATPase activity of Mcm2-7(3K499A) was similar to the wild type complex, but its interaction with single-stranded DNA in an electrophoretic mobility shift assay and its associations in cells were subtly altered. Together, these findings indicate that the PS1 hairpins in the Mcm2-7 subunits have important and distinct functions, most evident by the essential nature of the Mcm3 PS1 hairpin in DNA unwinding.
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Affiliation(s)
- Simon K. W. Lam
- Department of Biochemistry, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Xiaoli Ma
- Department of Biochemistry, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Tina L. Sing
- Department of Biochemistry, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Brian H. Shilton
- Department of Biochemistry, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Christopher J. Brandl
- Department of Biochemistry, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada
- * E-mail:
| | - Megan J. Davey
- Department of Biochemistry, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada
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10
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Frigola J, Remus D, Mehanna A, Diffley JFX. ATPase-dependent quality control of DNA replication origin licensing. Nature 2013; 495:339-43. [PMID: 23474987 PMCID: PMC4825857 DOI: 10.1038/nature11920] [Citation(s) in RCA: 163] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Accepted: 01/17/2013] [Indexed: 11/13/2022]
Abstract
The regulated loading of the Mcm2-7 DNA helicase (comprising six related subunits, Mcm2 to Mcm7) into pre-replicative complexes at multiple replication origins ensures precise once per cell cycle replication in eukaryotic cells. The origin recognition complex (ORC), Cdc6 and Cdt1 load Mcm2-7 into a double hexamer bound around duplex DNA in an ATP-dependent reaction, but the molecular mechanism of this origin 'licensing' is still poorly understood. Here we show that both Mcm2-7 hexamers in Saccharomyces cerevisiae are recruited to origins by an essential, conserved carboxy-terminal domain of Mcm3 that interacts with and stimulates the ATPase activity of ORC-Cdc6. ATP hydrolysis can promote Mcm2-7 loading, but can also promote Mcm2-7 release if components are missing or if ORC has been inactivated by cyclin-dependent kinase phosphorylation. Our work provides new insights into how origins are licensed and reveals a novel ATPase-dependent mechanism contributing to precise once per cell cycle replication.
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Affiliation(s)
- Jordi Frigola
- Cancer Research UK London Research Institute, Clare Hall Laboratories, South Mimms EN6 3LD, UK
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11
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Pan M, Santangelo TJ, Li Z, Reeve JN, Kelman Z. Thermococcus kodakarensis encodes three MCM homologs but only one is essential. Nucleic Acids Res 2011; 39:9671-80. [PMID: 21821658 PMCID: PMC3239210 DOI: 10.1093/nar/gkr624] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The minichromosome maintenance (MCM) complex is thought to function as the replicative helicase in archaea and eukaryotes. In eukaryotes, this complex is an assembly of six different but related polypeptides (MCM2-7) but, in most archaea, one MCM protein assembles to form a homohexameric complex. Atypically, the Thermococcus kodakarensis genome encodes three archaeal MCM homologs, here designated MCM1-3, although MCM1 and MCM2 are unusual in having long and unique N-terminal extensions. The results reported establish that MCM2 and MCM3 assemble into homohexamers and exhibit DNA binding, helicase and ATPase activities in vitro typical of archaeal MCMs. In contrast, MCM1 does not form homohexamers and although MCM1 binds DNA and has ATPase activity, it has only minimal helicase activity in vitro. Removal of the N-terminal extension had no detectable effects on MCM1 but increased the helicase activity of MCM2. A T. kodakarensis strain with the genes TK0096 (MCM1) and TK1361 (MCM2) deleted has been constructed that exhibits no detectable defects in growth or viability, but all attempts to delete TK1620 (MCM3) have been unsuccessful arguing that that MCM3 is essential and is likely the replicative helicase in T. kodakarensis. The origins and possible function(s) of the three MCM proteins are discussed.
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Affiliation(s)
- Miao Pan
- Institute for Bioscience and Biotechnology Research, University of Maryland, 9600 Gudelsky Drive, Rockville, MD 20850, USA
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12
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Tran NQ, Pham XH, Tuteja R, Tuteja N. Inhibition of unwinding and ATPase activities of pea MCM6 DNA helicase by actinomycin and nogalamycin. PLANT SIGNALING & BEHAVIOR 2011; 6:327-9. [PMID: 21336027 PMCID: PMC3142409 DOI: 10.4161/psb.6.3.13355] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Accepted: 08/18/2010] [Indexed: 05/30/2023]
Abstract
Pea mini-chromosome maintenance 6 (MCM6) single subunit (93 kDa) forms homohexamer (560 kDa) and contains an ATP-dependent and replication fork stimulated 3' to 5' DNA unwinding activity along with intrinsic DNA-dependent ATPase and ATP-binding activities [Plant Mol. Biol. 2010; DOI: 10.1007/s11103-010-9675-7]. Here, we have determined the effect of various DNA-binding agents, such as actinomycin, nogalamycin, daunorubicin, doxorubicin, distamycin, camptothecin, cyclophosphamide, ellipticine, VP-16, novobiocin, netropsin, cisplatin, mitoxantrone and genistein on the DNA unwinding and ATPase activities of the pea MCM6 DNA helicase. The results show that actinomycin and nogalamycin inhibited the DNA helicase (apparent Ki values of 10 and 1 μM, respectively) and ATPase (apparent Ki values of 100 and 17 μM, respectively) activities. Although, daunorubicin and doxorubicin also inhibited the DNA helicase activity of pea MCM6, but with less efficiency; however, these could not inhibit the ATPase activity. These results suggest that the intercalation of the inhibitors into duplex DNA generates a complex that impedes translocation of MCM6, resulting in the inhibitions of the activities. This study could be useful in our better understanding of the mechanism of plant nuclear DNA helicase unwinding.
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Affiliation(s)
- Ngoc Quang Tran
- International Centre for Genetic Engineering and Biotechnology, New Delhi, India
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13
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Brewster AS, Chen XS. Insights into the MCM functional mechanism: lessons learned from the archaeal MCM complex. Crit Rev Biochem Mol Biol 2010; 45:243-56. [PMID: 20441442 DOI: 10.3109/10409238.2010.484836] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The helicase function of the minichromosome maintenance protein (MCM) is essential for genomic DNA replication in archaea and eukaryotes. There has been rapid progress in studies of the structure and function of MCM proteins from different organisms, leading to better understanding of the MCM helicase mechanism. Because there are a number of excellent reviews on this topic, we will use this review to summarize some of the recent progress, with particular focus on the structural aspects of MCM and their implications for helicase function. Given the hexameric and double hexameric architecture observed by X-ray crystallography and electron microscopy of MCMs from archaeal and eukaryotic cells, we summarize and discuss possible unwinding modes by either a hexameric or a double hexameric helicase. Additionally, our recent crystal structure of a full length archaeal MCM has provided structural information on an intact, multi-domain MCM protein, which includes the salient features of four unusual beta-hairpins from each monomer, and the side channels of a hexamer/double hexamer. These new structural data enable a closer examination of the structural basis of the unwinding mechanisms by MCM.
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Affiliation(s)
- Aaron S Brewster
- Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089, USA
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14
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Jee J, Mizuno T, Kamada K, Tochio H, Chiba Y, Yanagi KI, Yasuda G, Hiroaki H, Hanaoka F, Shirakawa M. Structure and mutagenesis studies of the C-terminal region of licensing factor Cdt1 enable the identification of key residues for binding to replicative helicase Mcm proteins. J Biol Chem 2010; 285:15931-40. [PMID: 20335175 DOI: 10.1074/jbc.m109.075333] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
In eukaryotes, DNA replication is fired once in a single cell cycle before cell division starts to maintain stability of the genome. This event is tightly controlled by a series of proteins. Cdt1 is one of the licensing factors and is involved in recruiting replicative DNA helicase Mcm2-7 proteins into the pre-replicative complex together with Cdc6. In Cdt1, the C-terminal region serves as a binding site for Mcm2-7 proteins, although the details of these interactions remain largely unknown. Here, we report the structure of the region and the key residues for binding to Mcm proteins. We determined the solution structure of the C-terminal fragment, residues 450-557, of mouse Cdt1 by NMR. The structure consists of a winged-helix domain and shows unexpected similarity to those of the C-terminal domain of Cdc6 and the central fragment of Cdt1, thereby implying functional and evolutionary relationships. Structure-based mutagenesis and an in vitro binding assay enabled us to pinpoint the region that interacts with Mcm proteins. Moreover, by performing in vitro binding and budding yeast viability experiments, we showed that approximately 45 residues located in the N-terminal direction of the structural region are equally crucial for recognizing Mcm proteins. Our data suggest the possibility that winged-helix domain plays a role as a common module to interact with replicative helicase in the DNA replication-licensing process.
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Affiliation(s)
- Jungoo Jee
- Center for Priority Areas, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397, Japan.
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15
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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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16
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Sakakibara N, Kelman LM, Kelman Z. Unwinding the structure and function of the archaeal MCM helicase. Mol Microbiol 2009; 72:286-96. [DOI: 10.1111/j.1365-2958.2009.06663.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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17
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Snyder M, Huang XY, Zhang JJ. The minichromosome maintenance proteins 2-7 (MCM2-7) are necessary for RNA polymerase II (Pol II)-mediated transcription. J Biol Chem 2009; 284:13466-13472. [PMID: 19318354 DOI: 10.1074/jbc.m809471200] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The MCM2-7 (minichromosome maintenance) proteins are a family of evolutionarily highly conserved proteins. They are essential for DNA replication in yeast and are considered to function as DNA helicases. However, it has long been shown that there is an overabundance of the MCM2-7 proteins when compared with the number of DNA replication origins in chromatin. It has been suggested that the MCM2-7 proteins may function in other biological processes that require the unwinding of the DNA helix. In this report, we show that RNA polymerase II (Pol II)-mediated transcription is dependent on MCM5 and MCM2 proteins. Furthermore, the MCM2-7 proteins are co-localized with RNA Pol II on chromatins of constitutively transcribing genes, and MCM5 is required for transcription elongation of RNA Pol II. Finally, we demonstrate that the integrity of the MCM2-7 hexamer complex and the DNA helicase domain in MCM5 are essential for the process of transcription.
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Affiliation(s)
- Marylynn Snyder
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, New York 10065
| | - Xin-Yun Huang
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, New York 10065
| | - J Jillian Zhang
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, New York 10065.
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18
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Abstract
The connection between DNA replication and heterochromatic silencing in yeast has been a topic of investigation for >20 years. While early studies showed that silencing requires passage through S phase and implicated several DNA replication factors in silencing, later works showed that silent chromatin could form without DNA replication. In this study we show that members of the replicative helicase (Mcm3 and Mcm7) play a role in silencing and physically interact with the essential silencing factor, Sir2, even in the absence of DNA replication. Another replication factor, Mcm10, mediates the interaction between these replication and silencing proteins via a short C-terminal domain. Mutations in this region of Mcm10 disrupt the interaction between Sir2 and several of the Mcm2-7 proteins. While such mutations caused silencing defects, they did not cause DNA replication defects or affect the association of Sir2 with chromatin. Our findings suggest that Mcm10 is required for the coupling of the replication and silencing machineries to silence chromatin in a context outside of DNA replication beyond the recruitment and spreading of Sir2 on chromatin.
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19
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Cho JH, Kim HB, Kim HS, Choi SB. Identification and characterization of a rice MCM2 homologue required for DNA replication. BMB Rep 2008; 41:581-6. [PMID: 18755073 DOI: 10.5483/bmbrep.2008.41.8.581] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The pre-replication complex (pre-RC), including the core hexameric MCM2-7 complex, ensures that the eukaryotic genome is replicated only once per cell division cycle. In this study, we identified a rice minichromosome maintenance (MCM) homologue (OsMCM2) that functionally complemented fission yeast MCM2 (CDC19) mutants. We found OsMCM2 transcript expression in roots, leaves, and seeds, although expression levels differed slightly among the organs. Likewise, the OsMCM2 protein was ubiquitously expressed, but it was downregulated when nutritients were limiting, indicating that MCM2 expression (and therefore cell cycle progression) requires adequate nutrition. Yeast two-hybrid and GST pull-down assays demonstrated that OsMCM2 interacted with the COP9 signalosome 5 (CSN5). Taken as a whole, our results indicated that OsMCM2 functions as a subunit of the rice MCM complex and interacts with CSN5 during developmental regulation.
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Affiliation(s)
- Jae Han Cho
- Department of Biological Sciences, Myongji University, Yongin, Korea
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20
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Shin JH, Heo GY, Kelman Z. The Methanothermobacter thermautotrophicus MCM helicase is active as a hexameric ring. J Biol Chem 2008; 284:540-546. [PMID: 19001412 DOI: 10.1074/jbc.m806803200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The minichromosome maintenance (MCM) complex is thought to function as the replicative helicase in archaea and eukarya. The structure of the single MCM protein homologue from the archaeon Methanothermobacter thermautotrophicus is not yet clear, and hexameric, heptameric, octameric, and dodecameric structures, open rings, and filamentous structures have been reported. Using a combination of biochemical and structural analysis, it is shown here that the M. thermautotrophicus MCM helicase is active as a hexamer.
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Affiliation(s)
- Jae-Ho Shin
- Division of Applied Biology and Chemistry, College of Agriculture and Life Sciences, Kyungpook National University, 1370 Sankyuk-Dong, Daegu 702-701, Republic of Korea and the University of Maryland Biotechnology Institute, Center for Advanced Research in Biotechnology, Rockville, Maryland 20850
| | - Gun-Young Heo
- Division of Applied Biology and Chemistry, College of Agriculture and Life Sciences, Kyungpook National University, 1370 Sankyuk-Dong, Daegu 702-701, Republic of Korea and the University of Maryland Biotechnology Institute, Center for Advanced Research in Biotechnology, Rockville, Maryland 20850
| | - Zvi Kelman
- Division of Applied Biology and Chemistry, College of Agriculture and Life Sciences, Kyungpook National University, 1370 Sankyuk-Dong, Daegu 702-701, Republic of Korea and the University of Maryland Biotechnology Institute, Center for Advanced Research in Biotechnology, Rockville, Maryland 20850.
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21
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The DNA replication checkpoint aids survival of plants deficient in the novel replisome factor ETG1. EMBO J 2008; 27:1840-51. [PMID: 18528439 DOI: 10.1038/emboj.2008.107] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2008] [Accepted: 05/07/2008] [Indexed: 12/23/2022] Open
Abstract
Complete and accurate chromosomal DNA replication is essential for the maintenance of the genetic integrity of all organisms. Errors in replication are buffered by the activation of DNA stress checkpoints; however, in plants, the relative importance of a coordinated induction of DNA repair and cell cycle-arresting genes in the survival of replication mutants is unknown. In a systematic screen for Arabidopsis thaliana E2F target genes, the E2F TARGET GENE 1 (ETG1) was identified as a novel evolutionarily conserved replisome factor. ETG1 was associated with the minichromosome maintenance complex and was crucial for efficient DNA replication. Plants lacking the ETG1 gene had serrated leaves due to cell cycle inhibition triggered by the DNA replication checkpoints, as shown by the transcriptional induction of DNA stress checkpoint genes. The importance of checkpoint activation was highlighted by double mutant analysis: whereas etg1 mutant plants developed relatively normally, a synthetically lethal interaction was observed between etg1 and the checkpoint mutants wee1 and atr, demonstrating that activation of a G2 cell cycle checkpoint accounts for survival of ETG1-deficient plants.
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22
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Sakakibara N, Kasiviswanathan R, Melamud E, Han M, Schwarz FP, Kelman Z. Coupling of DNA binding and helicase activity is mediated by a conserved loop in the MCM protein. Nucleic Acids Res 2008; 36:1309-20. [PMID: 18184696 PMCID: PMC2275104 DOI: 10.1093/nar/gkm1160] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Minichromosome maintenance (MCM) helicases are the presumptive replicative helicases, thought to separate the two strands of chromosomal DNA during replication. In archaea, the catalytic activity resides within the C-terminal region of the MCM protein. In Methanothermobacter thermautotrophicus the N-terminal portion of the protein was shown to be involved in protein multimerization and binding to single and double stranded DNA. MCM homologues from many archaeal species have highly conserved predicted amino acid similarity in a loop located between β7 and β8 in the N-terminal part of the molecule. This high degree of conservation suggests a functional role for the loop. Mutational analysis and biochemical characterization of the conserved residues suggest that the loop participates in communication between the N-terminal portion of the helicase and the C-terminal catalytic domain. Since similar residues are also conserved in the eukaryotic MCM proteins, the data presented here suggest a similar coupling between the N-terminal and catalytic domain of the eukaryotic enzyme.
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Affiliation(s)
- Nozomi Sakakibara
- University of Maryland Biotechnology Institute, Center for Advanced Research in Biotechnology, 9600 Gudelsky Drive, Rockville, MD 20850, USA
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23
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Sheu YJ, Stillman B. Cdc7-Dbf4 phosphorylates MCM proteins via a docking site-mediated mechanism to promote S phase progression. Mol Cell 2006; 24:101-13. [PMID: 17018296 PMCID: PMC2923825 DOI: 10.1016/j.molcel.2006.07.033] [Citation(s) in RCA: 250] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2005] [Revised: 06/16/2006] [Accepted: 07/26/2006] [Indexed: 10/24/2022]
Abstract
Origins of DNA replication are licensed in G1 by recruiting the minichromosome maintenance (MCM) proteins to form a prereplicative complex (pre-RC). Prior to initiation of DNA synthesis from each origin, a preinitiation complex (pre-IC) containing Cdc45 and other proteins is formed. We report that Cdc7-Dbf4 protein kinase (DDK) promotes assembly of a stable Cdc45-MCM complex exclusively on chromatin in S phase. In this complex, Mcm4 is hyperphosphorylated. Studies in vitro using purified DDK and Mcm4 demonstrate that hyperphosphorylation occurs at the Mcm4 N terminus. However, the DDK substrate specificity is conferred by an adjacent DDK-docking domain (DDD), sufficient for facilitating efficient phosphorylation of artificial phosphoacceptors in cis. Genetic evidence suggests that phosphorylation of Mcm4 by DDK is important for timely S phase progression and for cell viability upon overproduction of Cdc45. We suggest that DDK docks on and phosphorylates MCM proteins at licensed origins to promote proper assembly of pre-IC.
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Affiliation(s)
- Yi-Jun Sheu
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
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24
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Reese DK, Meinke G, Kumar A, Moine S, Chen K, Sudmeier JL, Bachovchin W, Bohm A, Bullock PA. Analyses of the interaction between the origin binding domain from simian virus 40 T antigen and single-stranded DNA provide insights into DNA unwinding and initiation of DNA replication. J Virol 2006; 80:12248-59. [PMID: 17005644 PMCID: PMC1676264 DOI: 10.1128/jvi.01201-06] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
DNA helicases are essential for DNA metabolism; however, at the molecular level little is known about how they assemble or function. Therefore, as a model for a eukaryotic helicase, we are analyzing T antigen (T-ag) the helicase encoded by simian virus 40. In this study, nuclear magnetic resonance (NMR) methods were used to investigate the transit of single-stranded DNA (ssDNA) through the T-ag origin-binding domain (T-ag OBD). When the residues that interact with ssDNA are viewed in terms of the structure of a hexamer of the T-ag OBD, comprised of residues 131 to 260, they indicate that ssDNA passes over one face of the T-ag OBD and then transits through a gap in the open ring structure. The NMR-based conclusions are supported by an analysis of previously described mutations that disrupt critical steps during the initiation of DNA replication. These and related observations are discussed in terms of the threading of DNA through T-ag hexamers and the initiation of viral DNA replication.
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Affiliation(s)
- Danielle K Reese
- Department of Biochemistry A703, Tufts University School of Medicine, 136 Harrison Ave., Boston, MA 02111, USA
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25
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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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26
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Takahashi TS, Wigley DB, Walter JC. Pumps, paradoxes and ploughshares: mechanism of the MCM2-7 DNA helicase. Trends Biochem Sci 2006; 30:437-44. [PMID: 16002295 DOI: 10.1016/j.tibs.2005.06.007] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2005] [Revised: 05/23/2005] [Accepted: 06/22/2005] [Indexed: 11/30/2022]
Abstract
In eukaryotes, numerous lines of evidence have coalesced into a convincing case that the MCM2-7 complex - a heterohexameric ATPase - is the replicative DNA helicase. However, almost nothing is known about how this enzyme functions in a cellular context. Some models for the mechanism of the MCM2-7 helicase envision that it translocates along single-stranded DNA (ssDNA), whereas, more recently, it is has been suggested that it pumps double-stranded DNA (dsDNA) through its central channel. In particular, one model in which a double hexamer of MCM2-7 pumps dsDNA towards the hexamer interface and extrudes ssDNA laterally as a result of torsional strain is gaining popularity. Here, we discuss existing models and propose a new variation in which a single hexamer is the functional unit of the helicase. Duplex DNA is pumped into MCM2-7 and, as it emerges from the complex, a rigid protein that we term the 'ploughshare' splits the duplex.
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Affiliation(s)
- Tatsuro S Takahashi
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
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27
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Mahmud N, Rose D, Pang W, Walker R, Patil V, Weich N, Hoffman R. Characterization of primitive marrow CD34+ cells that persist after a sublethal dose of total body irradiation. Exp Hematol 2006; 33:1388-401. [PMID: 16263423 DOI: 10.1016/j.exphem.2005.07.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2005] [Revised: 07/06/2005] [Accepted: 07/11/2005] [Indexed: 01/23/2023]
Abstract
Knowledge of the molecular events that occur during hematopoietic stem/progenitor cell (HSPC) development is vital to our understanding of blood cell production. To study the functional groups of genes characteristic of HSPCs we isolated a subpopulation of CD34+ bone marrow (BM) cells from nonhuman primates that persisted in vivo after a sublethal dose of total body irradiation (TBI). CD34+ cells isolated during the phase of maximal hematopoietic suppression show a transcriptional profile characteristic of metabolically inactive cells, with strong coordinate downregulation of a large number of genes required for protein production and processing. Consistent with this profile, these CD34+ cells were not able to generate hematopoietic colonies. Transcriptional profiling of these CD34+ cells in conjunction with a pathway analysis method reveals several classes of functionally related genes that are upregulated in comparison to the CD34+ cells obtained prior to TBI. These families included genes known to be associated with self-renewal and maintenance of HSPCs (including bone morphogenetic proteins), resistance to apoptosis (Bcl-2) as well as genes characteristic of a variety of nonhematopoietic tissues (gamma-aminobutyric acid/glycine receptor, complement receptor C1qRp). In contrast, during the period of hematopoietic recovery, the CD34+ cells expressed higher level of genes encoding factors regulating maturation and differentiation of HSPCs. Our data indicate that the primitive BM CD34+ cell population that persists after radiation possesses a transcriptional profile suggestive of pluripotency.
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Affiliation(s)
- Nadim Mahmud
- University of Illinois College of Medicine, Chicago, IL 60607, USA.
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28
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Patterson S, Robert C, Whittle C, Chakrabarti R, Doerig C, Chakrabarti D. Pre-replication complex organization in the atypical DNA replication cycle of Plasmodium falciparum: Characterization of the mini-chromosome maintenance (MCM) complex formation. Mol Biochem Parasitol 2006; 145:50-9. [PMID: 16257456 DOI: 10.1016/j.molbiopara.2005.09.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2005] [Revised: 09/09/2005] [Accepted: 09/15/2005] [Indexed: 10/25/2022]
Abstract
The overall organization of cell division in Plasmodium is unique compared to that observed in model organisms because DNA replicates more than once per cell cycle at several points of its life cycle. The sequencing of the Plasmodium genome has also revealed the apparent absence of many key components (e.g. Cdt1, DDK and Cdc45) of the eukaryotic cell cycle machinery that are responsible for the formation of the pre-replication complex (pre-RC). We have characterized the Plasmodium falciparum minichromosome maintenance complex (MCM) that plays a key role in the transition of pre-RC to the RC. Similar to other eukaryotes, the Plasmodium genome encodes six MCM subunits. Here, we show that expression levels of at least three of the PfMCM subunits, the homologues of MCM2, MCM6 and MCM7, change during the intraerythrocytic development cycle, peaking in schizont and decreasing in the ring and trophozoite stages. PfMCM2, 6 and 7 subunits interact with each other to form a developmentally regulated complex: these interactions are detectable in rings and schizonts, but not in trophozoites. PfMCM2, 6 and 7 subunits are localized in both cytosolic and nucleosolic fractions during all intraerythrocytic stages of P. falciparum development, with increased nuclear localization in schizonts. Only PfMCM6 is associated with the chromatin fraction at all stages of growth. No phosphorylation of PfMCM2, 6 and 7 was detected, but two as yet unidentified threonine-phosphosphorylated proteins were present in the complex, whose pattern of phosphorylation varied during parasite development.
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Affiliation(s)
- Shelley Patterson
- Department of Molecular Biology and Microbiology, University of Central Florida, Orlando, FL 32826, USA
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29
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Gómez-Llorente Y, Fletcher RJ, Chen XS, Carazo JM, San Martín C. Polymorphism and double hexamer structure in the archaeal minichromosome maintenance (MCM) helicase from Methanobacterium thermoautotrophicum. J Biol Chem 2005; 280:40909-15. [PMID: 16221680 DOI: 10.1074/jbc.m509760200] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Methanobacterium thermoautotrophicum minichromosome maintenance complex (mtMCM), a cellular replicative helicase, is a useful model for the more complex eukaryotic MCMs. Biochemical and crystallographic evidence indicates that mtMCM assembles as a double hexamer (dHex), but previous electron microscopy studies reported only the presence of single heptamers or single hexamers (Pape, T., Meka, H., Chen, S., Vicentini, G., Van Heel, M., and Onesti, S. (2003) EMBO Rep. 4, 1079-1083; Yu, X., VanLoock, M. S., Poplawski, A., Kelman, Z., Xiang, T., Tye, B. K., and Egelman, E. H. (2002) EMBO Rep. 3, 792-797). Here we present the first three-dimensional electron microscopy reconstruction of the full-length mtMCM dHex in which two hexamers contact each other via the structurally well defined N-terminal domains. The dHex has obvious side openings that resemble the side channels of LTag (large T antigen). 6-fold and 7-fold rings were observed in the same mtMCM preparation, but we determined that assembly as a double ring favors 6-fold structures. Additionally, open rings were also detected, which suggests a direct mtMCM loading mechanism onto DNA.
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Affiliation(s)
- Yacob Gómez-Llorente
- Biocomputing Unit, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Darwin 3, 28049 Madrid, Spain
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30
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Fletcher RJ, Shen J, Gómez-Llorente Y, Martín CS, Carazo JM, Chen XS. Double hexamer disruption and biochemical activities of Methanobacterium thermoautotrophicum MCM. J Biol Chem 2005; 280:42405-10. [PMID: 16221679 DOI: 10.1074/jbc.m509773200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Methanobacterium thermoautotrophicum MCM (mtMCM) is a helicase required for DNA replication. Previous electron microscopy studies have shown mtMCM in several oligomeric forms. However, biochemical studies suggest that mtMCM is a dodecamer, likely a double hexamer (dHex). The crystal structure of the N-terminal fragment of mtMCM reveals a stable dHex architecture. To further confirm that the dHex is not an artifact of crystal packing of two hexamers, we investigated the relevance of the dHex by disrupting the hexamer-hexamer interactions seen in the crystal structure via site-directed mutagenesis and examining various biochemical activities of the mutants in vitro. Using a combination of biochemical and structural assays, we demonstrated that changing arginine to alanine at amino acid position 161 or the insertion of a six-aminoacid peptide at the hexamer-hexamer interface disrupted dHex formation and produced stable single hexamers (sHex). Furthermore, we showed that the sHex mutants retained wild-type level of ATPase and DNA binding activities but had decreased helicase activity when compared with the wild type dHex protein. These biochemical properties of mtMCM are reminiscent of those of SV40 large T antigen, suggesting that the dHex form of mtMCM may be the active helicase for DNA unwinding during the bidirectional DNA replication.
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Affiliation(s)
- Ryan J Fletcher
- Molecular and Computational Biology, University of Southern California, Los Angeles, California 90089, USA
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31
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Snyder M, He W, Zhang JJ. The DNA replication factor MCM5 is essential for Stat1-mediated transcriptional activation. Proc Natl Acad Sci U S A 2005; 102:14539-44. [PMID: 16199513 PMCID: PMC1253610 DOI: 10.1073/pnas.0507479102] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The eukaryotic minichromosome maintenance (MCM) family of proteins (MCM2-MCM7) is evolutionarily conserved from yeast to human. These proteins are essential for DNA replication. The signal transducer and activator of transcription proteins are critical for the signal transduction of a multitude of cytokines and growth factors leading to the regulation of gene expression. We previously identified a strong interaction between Stat1 and MCM5. However, the physiological significance of this interaction was not clear. We show here by chromatin immunoprecipitation (ChIP) analyses that the MCM5 protein, as well as other members of the MCM family, is inducibly recruited to Stat1 target gene promoters in response to cytokine stimulation. Furthermore, the MCM proteins are shown to move along with the RNA polymerase II during transcription elongation. We have also identified an independent domain in MCM5 that mediates the interaction between Stat1 and MCM5; overexpression of this domain can disrupt the interaction between Stat1 and MCM5 and inhibit Stat1 transcriptional activity. Finally, we used the RNA interference technique to show that MCM5 is essential for transcription activation of Stat1 target genes. Together, these results demonstrate that, in addition to their roles in DNA replication, the MCM proteins are also necessary for transcription activation.
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Affiliation(s)
- Marylynn Snyder
- Department of Pathology and Laboratory Medicine, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA
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32
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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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33
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Nieduszynski CA, Blow JJ, Donaldson AD. The requirement of yeast replication origins for pre-replication complex proteins is modulated by transcription. Nucleic Acids Res 2005; 33:2410-20. [PMID: 15860777 PMCID: PMC1087785 DOI: 10.1093/nar/gki539] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The mini-chromosome maintenance proteins Mcm2–7 are essential for DNA replication. They are loaded onto replication origins during G1 phase of the cell cycle to form a pre-replication complex (pre-RC) that licenses each origin for subsequent initiation. We have investigated the DNA elements that determine the dependence of yeast replication origins on Mcm2–7 activity, i.e. the sensitivity of an origin to mcm mutations. Using chimaeric constructs from mcm sensitive and mcm insensitive origins, we have identified two main elements affecting the requirement for Mcm2–7 function. First, transcription into an origin increases its dependence on Mcm2–7 function, revealing a conflict between pre-RC assembly and transcription. Second, sequence elements within the minimal origin influence its mcm sensitivity. Replication origins show similar differences in sensitivity to mutations in other pre-RC proteins (such as Origin Recognition Complex and Cdc6), but not to mutations in initiation and elongation factors, demonstrating that the mcm sensitivity of an origin is determined by its ability to establish a pre-RC. We propose that there is a hierarchy of replication origins with respect to the range of pre-RC protein concentrations under which they will function. This hierarchy is both ‘hard-wired’ by the minimal origin sequences and ‘soft-wired’ by local transcriptional context.
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Affiliation(s)
| | - J. Julian Blow
- Cancer Research UK Chromosome Replication Research Group, Wellcome Trust Biocentre, University of DundeeDow Street, Dundee DD1 5EH, Scotland, UK
| | - Anne D. Donaldson
- To whom correspondence should be addressed. Tel: +44 0 1224 550975; Fax: +44 0 1224 555844;
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34
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Stillman B. Origin recognition and the chromosome cycle. FEBS Lett 2005; 579:877-84. [PMID: 15680967 DOI: 10.1016/j.febslet.2004.12.011] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2004] [Revised: 12/10/2004] [Accepted: 12/10/2004] [Indexed: 11/29/2022]
Abstract
Prior to the initiation of DNA replication, chromosomes must establish a biochemical mark that permits the recruitment in S phase of the DNA replication machinery that copies DNA. The process of chromosome replication in eukaryotes also must be coordinated with segregation of the duplicated chromosomes to daughter cells during mitosis. Protein complexes that utilize ATP coordinate events at origins of DNA replication and later they participate in the initiation of DNA replication. In eukaryotes, some of these proteins also play a part in later processes that ensure accurate inheritance of chromosomes in mitosis, including spindle attachment of chromosomes, accurate duplication of centrosomes and cytokinesis. A perspective of how ATP-dependent proteins accomplish this task in eukaryotes is discussed.
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Affiliation(s)
- Bruce Stillman
- Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA.
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35
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Chen YJ, Yu X, Kasiviswanathan R, Shin JH, Kelman Z, Egelman EH. Structural Polymorphism of Methanothermobacter thermautotrophicus MCM. J Mol Biol 2005; 346:389-94. [PMID: 15670590 DOI: 10.1016/j.jmb.2004.11.076] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2004] [Revised: 11/24/2004] [Accepted: 11/30/2004] [Indexed: 11/24/2022]
Abstract
The minichromosome maintenance (MCM) proteins are essential for replication initiation and elongation in eukarya and archaea. There are six MCM proteins in eukaryotes, and MCM complexes are believed to unwind DNA during chromosomal DNA replication. However, the mechanism and structure of the MCM complexes are not known. Only one MCM is found in the archaeon Methanothermobacter thermautotrophicus (mtMCM), and this provides a simpler system for study. The crystal structure of a mtMCM N-terminal fragment has been solved, but surprisingly only subtle structural changes were seen between the wild-type protein and one having a mutation corresponding to the yeast MCM5 bob1 mutation. The bob1 mutation bypasses the phosphorylation required for activation of MCM in yeast. We have used electron microscopy and three-dimensional reconstruction to examine a number of different fragments of mtMCM, and can visualize a large conformational change within the N-terminal fragment. This offers new insight into the conformational dynamics of MCM and the phosphorylation-bypass phenotype in yeast.
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Affiliation(s)
- Yen-Ju Chen
- Department of Biochemistry and Molecular Genetics, Box 800733, University Of Virginia Health Sciences Center, Charlottesville, VA 22908, USA
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36
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De Felice M, Esposito L, Pucci B, De Falco M, Manco G, Rossi M, Pisani F. Modular organization of a Cdc6-like protein from the crenarchaeon Sulfolobus solfataricus. Biochem J 2004; 381:645-53. [PMID: 15104537 PMCID: PMC1133873 DOI: 10.1042/bj20040280] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2004] [Revised: 03/25/2004] [Accepted: 04/23/2004] [Indexed: 01/08/2023]
Abstract
In the present paper, we report that a Cdc6 (cell-division control)-like factor from the hyperthermophilic crenarchaeon Sulfolobus solfataricus (referred to as SsoCdc6-2) has a modular organization of its biological functions. A reliable model of the SsoCdc6-2 three-dimensional structure was built up, based on the significant sequence identity with the Pyrobaculum aerophylum Cdc6 (PaeCdc6), whose crystallographic structure is known. This allowed us to design two truncated forms of SsoCdc6-2: the DeltaC (residues 1-297, molecular mass 35 kDa) and the DeltaN (residues 298-400, molecular mass 11 kDa) proteins. The DeltaC protein contains the nucleotide-binding Rossmann fold and the Sensor-2 motif (Domains I and II in the PaeCdc6 structure), and retains the ability to bind and hydrolyse ATP. On the other hand, the DeltaN protein contains the C-terminal WH (winged helix)-fold (Domain III), and is able to bind DNA molecules and to inhibit the DNA helicase activity of the SsoMCM (mini-chromosome maintenance) complex, although with lesser efficiency with respect to the full-sized SsoCdc6-2. These results provide direct biochemical evidence that the Cdc6 WH-domain is responsible for DNA-binding and inhibition of MCM DNA helicase activity.
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Affiliation(s)
- Mariarita De Felice
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via P. Castellino 111, 80131-Napoli, Italy
| | - Luca Esposito
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via P. Castellino 111, 80131-Napoli, Italy
| | - Biagio Pucci
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via P. Castellino 111, 80131-Napoli, Italy
| | - Mariarosaria De Falco
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via P. Castellino 111, 80131-Napoli, Italy
| | - Giuseppe Manco
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via P. Castellino 111, 80131-Napoli, Italy
| | - Mosè Rossi
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via P. Castellino 111, 80131-Napoli, Italy
| | - Francesca M. Pisani
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via P. Castellino 111, 80131-Napoli, Italy
- To whom correspondence should be addressed (e-mail )
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37
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Shechter D, Ying CY, Gautier J. DNA unwinding is an Mcm complex-dependent and ATP hydrolysis-dependent process. J Biol Chem 2004; 279:45586-93. [PMID: 15326181 DOI: 10.1074/jbc.m407772200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Minichromosome maintenance proteins (Mcm) are essential in all eukaryotes and are absolutely required for initiation of DNA replication. The eukaryotic and archaeal Mcm proteins have conserved helicase motifs and exhibit DNA helicase and ATP hydrolysis activities in vitro. Although the Mcm proteins have been proposed to be the replicative helicase, the enzyme that melts the DNA helix at the replication fork, their function during cellular DNA replication elongation is still unclear. Using nucleoplasmic extract (NPE) from Xenopus laevis eggs and six purified polyclonal antibodies generated against each of the Xenopus Mcm proteins, we have demonstrated that Mcm proteins are required during DNA replication and DNA unwinding after initiation of replication. Quantitative depletion of Mcms from the NPE results in normal replication and unwinding, confirming that Mcms are required before pre-replicative complex assembly and dispensable thereafter. Replication and unwinding are inhibited when pooled neutralizing antibodies against the six different Mcm2-7 proteins are added during NPE incubation. Furthermore, replication is blocked by the addition of the Mcm antibodies after an initial period of replication in the NPE, visualized by a pulse of radiolabeled nucleotide at the same time as antibody addition. Addition of the cyclin-dependent kinase 2 inhibitor p21(cip1) specifically blocks origin firing but does not prevent helicase action. When p21(cip1) is added, followed by the non-hydrolyzable analog ATPgammaS to block helicase function, unwinding is inhibited, demonstrating that plasmid unwinding is specifically attributable to an ATP hydrolysis-dependent function. These data support the hypothesis that the Mcm protein complex functions as the replicative helicase.
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Affiliation(s)
- David Shechter
- Integrated Program in Cellular, Molecular, and Biophysical Studies, Department of Genetics and Development, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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38
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Reverdatto SV, Dutko JA, Chekanova JA, Hamilton DA, Belostotsky DA. mRNA deadenylation by PARN is essential for embryogenesis in higher plants. RNA (NEW YORK, N.Y.) 2004; 10:1200-14. [PMID: 15247430 PMCID: PMC1370610 DOI: 10.1261/rna.7540204] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Deadenylation of mRNA is often the first and rate-limiting step in mRNA decay. PARN, a poly(A)-specific 3' --> 5' ribonuclease which is conserved in many eukaryotes, has been proposed to be primarily responsible for such a reaction, yet the importance of the PARN function at the whole-organism level has not been demonstrated in any species. Here, we show that mRNA deadenylation by PARN is essential for viability in higher plants (Arabidopsis thaliana). Yet, this essential requirement for the PARN function is not universal across the phylogenetic spectrum, because PARN is dispensable in Fungi (Schizosaccharomyces pombe), and can be at least severely downregulated without any obvious consequences in Metazoa (Caenorhabditis elegans). Development of the Arabidopsis embryos lacking PARN (AtPARN), as well as of those expressing an enzymatically inactive protein, was markedly retarded, and ultimately culminated in an arrest at the bent-cotyledon stage. Importantly, only some, rather than all, embryo-specific transcripts were hyperadenylated in the mutant embryos, suggesting that preferential deadenylation of a specific select subset of mRNAs, rather than a general deadenylation of the whole mRNA population, by AtPARN is indispensable for embryogenesis in Arabidopsis. These findings indicate a unique, nonredundant role of AtPARN among the multiple plant deadenylases.
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Affiliation(s)
- Sergei V Reverdatto
- Department of Biological Sciences, State University of New York at Albany, 12222, USA
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39
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Abstract
DNA helicases are molecular 'motor' enzymes that use the energy of NTP hydrolysis to separate transiently energetically stable duplex DNA into single strands. They are therefore essential in nearly all DNA metabolic transactions. They act as essential molecular tools for the cellular machinery. Since the discovery of the first DNA helicase in Escherichia coli in 1976, several have been isolated from both prokaryotic and eukaryotic systems. DNA helicases generally bind to ssDNA or ssDNA/dsDNA junctions and translocate mainly unidirectionally along the bound strand and disrupt the hydrogen bonds between the duplexes. Most helicases contain conserved motifs which act as an engine to drive DNA unwinding. Crystal structures have revealed an underlying common structural fold for their function. These structures suggest the role of the helicase motifs in catalytic function and offer clues as to how these proteins can translocate and unwind DNA. The genes containing helicase motifs may have evolved from a common ancestor. In this review we cover the conserved motifs, structural information, mechanism of DNA unwinding and translocation, and functional aspects of DNA helicases.
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Affiliation(s)
- Narendra Tuteja
- International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India.
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40
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Kasiviswanathan R, Shin JH, Melamud E, Kelman Z. Biochemical Characterization of the Methanothermobacter thermautotrophicus Minichromosome Maintenance (MCM) Helicase N-terminal Domains. J Biol Chem 2004; 279:28358-66. [PMID: 15100218 DOI: 10.1074/jbc.m403202200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Minichromosome maintenance helicases are ring-shaped complexes that play an essential role in archaeal and eukaryal DNA replication by separating the two strands of chromosomal DNA to provide the single-stranded substrate for the replicative polymerases. For the archaeal protein it was shown that the N-terminal portion of the protein, which is composed of domains A, B, and C, is involved in multimer formation and single-stranded DNA binding and may also play a role in regulating the helicase activity. Here, a detailed biochemical characterization of the N-terminal region of the Methanothermobacter thermautotrophicus minichromosome maintenance helicase is described. Using biochemical and biophysical analyses it is shown that domain C of the N-terminal portion, located adjacent to the helicase catalytic domains, is required for protein multimerization and that domain B is the main contact region with single-stranded DNA. It is also shown that although oligomerization is not essential for single-stranded DNA binding and ATPase activity, the presence of domain C is essential for helicase activity.
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Affiliation(s)
- Rajesh Kasiviswanathan
- Center for Advanced Research in Biotechnology, University of Maryland Biotechnology Institute, 9600 Gudelsky Drive, Rockville, MD 20850, USA
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41
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Abstract
The minichromosome maintenance (or MCM) protein family is composed of six related proteins that are conserved in all eukaryotes. They were first identified by genetic screens in yeast and subsequently analyzed in other experimental systems using molecular and biochemical methods. Early data led to the identification of MCMs as central players in the initiation of DNA replication. More recent studies have shown that MCM proteins also function in replication elongation, probably as a DNA helicase. This is consistent with structural analysis showing that the proteins interact together in a heterohexameric ring. However, MCMs are strikingly abundant and far exceed the stoichiometry of replication origins; they are widely distributed on unreplicated chromatin. Analysis of mcm mutant phenotypes and interactions with other factors have now implicated the MCM proteins in other chromosome transactions including damage response, transcription, and chromatin structure. These experiments indicate that the MCMs are central players in many aspects of genome stability.
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Affiliation(s)
- Susan L Forsburg
- Molecular & Cell Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA.
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42
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Shin JH, Jiang Y, Grabowski B, Hurwitz J, Kelman Z. Substrate requirements for duplex DNA translocation by the eukaryal and archaeal minichromosome maintenance helicases. J Biol Chem 2003; 278:49053-62. [PMID: 12975364 DOI: 10.1074/jbc.m308599200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Replicative DNA helicases are ring-shaped hexamers that play an essential role in DNA synthesis by separating the two strands of chromosomal DNA to provide the single-stranded (ss) substrate for replicative polymerases. Biochemical and structural studies suggest that these helicases translocate along one strand of the duplex, which passes through and interacts with the central channel of these ring-shaped hexamers, and displace the complementary strand. A number of these helicases were shown to also encircle both strands simultaneously and then translocate along double-stranded (ds)DNA. In this report it is shown that the Schizosaccharomyces pombe Mcm4,6,7 complex and archaeal minichromosome maintenance (MCM) helicase from Methanothermobacter thermautotrophicus move along duplex DNA. These two helicases, however, differ in the substrate required to support dsDNA translocation. Although the S. pombe Mcm4,6,7 complex required a 3'-overhang ssDNA region to initiate its association with the duplex, the archaeal protein initiated its transit along dsDNA in the absence of a 3'-overhang region, as well. Furthermore, DNA substrates containing a streptavidin-biotin steric block inhibited the movement of the eukaryotic helicase along ss and dsDNAs but not of the archaeal enzyme. The M. thermautotrophicus MCM helicase, however, was shown to displace a streptavidin-biotin complex from ss, as well as dsDNAs. The possible roles of dsDNA translocation by the MCM proteins during the initiation and elongation phases of chromosomal replication are discussed.
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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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43
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Abstract
Initiator proteins are key components of the DNA replication machinery that determine where initiation will occur. In the past few years, due to a greatly improved understanding of what viral initiators look like and how they function, we can now identify the basic tasks that are required of initiators, as well as begin to comprehend what activities are required to perform these tasks. The improved knowledge of the viral initiators also demonstrates an unexpected level of conservation between different viral initiators, which might extend also to their cellular counterparts.
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Affiliation(s)
- Arne Stenlund
- Cold Spring Harbor Laboratory, P.O. Box 100, 1 Bungtown Rd, Cold Spring Harbor, New York 11724, USA.
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44
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Yoshida K, Inoue I. Conditional expression of MCM7 increases tumor growth without altering DNA replication activity. FEBS Lett 2003; 553:213-7. [PMID: 14550576 DOI: 10.1016/s0014-5793(03)01018-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The minichromosome maintenance (MCM) 2-7 complex is a putative DNA helicase complex that facilitates the initiation of DNA replication. Here, we generated a cell line MCM7(+/-)/MCM7-FLAG, in which one allele of MCM7 is mutated whereas a tetracycline-repressible promoter could manipulate the expression of exogenous MCM7 protein. Overexpressed MCM7 protein supports efficient DNA replication of Epstein-Barr virus oriP and rapid formation of tumors in nude mice without altering the activity of cellular DNA replication. This system provides a unique setting for studying the function of MCM7 and for screening for potential therapeutics for malignant tumors.
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Affiliation(s)
- Kenichi Yoshida
- Genetic Diagnosis, Institute of Medical Science, University of Tokyo, Japan.
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45
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Shin JH, Grabowski B, Kasiviswanathan R, Bell SD, Kelman Z. Regulation of minichromosome maintenance helicase activity by Cdc6. J Biol Chem 2003; 278:38059-67. [PMID: 12837750 DOI: 10.1074/jbc.m305477200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Genetic studies, together with amino acid and structural similarities to the clamp loaders of DNA polymerase sliding clamps, have suggested that the Cdc6 protein may function as a loader for the eukaryotic replicative helicase, the minichromosome maintenance (MCM) complex. Thus, Cdc6 may act as the functional homologue of the bacterial DnaC that utilizes ATP hydrolysis to assemble the DnaB helicase at the origin. This report shows that the helicase activity of an MCM homologue from the archaeon Methanothermobacter thermautotrophicus is inhibited in the presence of the Cdc6 homologues. This inhibitory activity is dependent, as for DnaC, on ATP binding to Cdc6. Moreover, an intact Cdc6 winged helix domain is required for efficient inhibition. Two-hybrid analyses indicated that MCM and Cdc6 interact and that the interaction is mediated by the winged helix domain. Analysis of Cdc6 and MCM homologues from several archaea exhibited differences in the inhibitory activity suggesting divergence in function in Cdc6 and MCM homologues among the archaea.
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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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46
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Cook CR, Kung G, Peterson FC, Volkman BF, Lei M. A novel zinc finger is required for Mcm10 homocomplex assembly. J Biol Chem 2003; 278:36051-8. [PMID: 12844493 DOI: 10.1074/jbc.m306049200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mcm10 is a DNA replication factor that interacts with multiple subunits of the MCM2-7 hexameric complex. We report here that Mcm10 self-interacts and assembles into large homocomplexes (approximately 800 kDa). A conserved domain of 210 amino acid residues is sufficient for mediating self-interaction and complex assembly. A novel zinc finger within the conserved domain, CX10CX11CX2H, is essential for the homocomplex formation. Mutant alleles with amino acid substitutions at conserved cysteines and histidine in the zinc finger fail to assemble homocomplexes. A defect in homocomplex assembly correlates with defects in DNA replication and cell growth in the mutants. These observations suggest that homocomplex assembly is essential for Mcm10 function. Multisubunit Mcm10 homocomplexes may provide the structural basis for Mcm10 to interact with multiple subunits of the MCM2-7 hexamer.
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Affiliation(s)
- Craig R Cook
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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47
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Fitch MJ, Donato JJ, Tye BK. Mcm7, a subunit of the presumptive MCM helicase, modulates its own expression in conjunction with Mcm1. J Biol Chem 2003; 278:25408-16. [PMID: 12738768 DOI: 10.1074/jbc.m300699200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Saccharomyces cerevisiae Mcm7 protein is a subunit of the presumed heteromeric MCM helicase that melts origin DNA and unwinds replication forks. Previous work showed that Mcm1 binds constitutively to the MCM7 promoter and regulates MCM7 expression. Here, we identify Mcm7 as a novel cofactor of Mcm1 in the regulation of MCM7 expression. Transcription of MCM7 is increased in the mcm7-1 mutant and decreased in the mcm1-1 mutant, suggesting that Mcm7 modulates its own expression in conjunction with Mcm1. Indeed, Mcm7 stimulates Mcm1 binding to the early cell cycle box upstream of the promoters of MCM7 as well as CDC6 and MCM5. Whereas Mcm1 binds these promoters constitutively, Mcm7 is recruited during late M phase, consistent with Mcm7 playing a direct role in modulating the periodic expression of early cell cycle genes. The multiple roles of Mcm7 in replication initiation, replication elongation, and autoregulation parallel those of the oncoprotein, the large T-antigen of the SV40 virus.
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Affiliation(s)
- Michael J Fitch
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853-2703, USA
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48
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Ishimi Y, Komamura-Kohno Y, Kwon HJ, Yamada K, Nakanishi M. Identification of MCM4 as a target of the DNA replication block checkpoint system. J Biol Chem 2003; 278:24644-50. [PMID: 12714602 DOI: 10.1074/jbc.m213252200] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Inhibition of the progression of DNA replication prevents further initiation of DNA replication and allows cells to maintain arrested replication forks, but the proteins that are targets of the replication checkpoint system remain to be identified. We report here that human MCM4, a subunit of the putative DNA replicative helicase, is extensively phosphorylated in HeLa cells when they are incubated in the presence of inhibitors of DNA synthesis or are exposed to UV irradiation. The data presented here indicate that the consecutive actions of ATR-CHK1 and CDK2 kinases are involved in this phosphorylation in the presence of hydroxyurea. The phosphorylation sites in MCM4 were identified using specific anti-phosphoantibodies. Based on results that showed that the DNA helicase activity of the MCM4-6-7 complex is negatively regulated by CDK2 phosphorylation, we suggest that the phosphorylation of MCM4 in the checkpoint control inhibits DNA replication, which includes blockage of DNA fork progression, through inactivation of the MCM complex.
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Affiliation(s)
- Yukio Ishimi
- Biomolecular and Technology Department, Mitsubishi Kagaku Institute of Life Sciences, 11 Minamiooya, Machida, Tokyo 194-8511, Japan.
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Araki Y, Kawasaki Y, Sasanuma H, Tye BK, Sugino A. Budding yeast mcm10/dna43 mutant requires a novel repair pathway for viability. Genes Cells 2003; 8:465-80. [PMID: 12694535 DOI: 10.1046/j.1365-2443.2003.00648.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND MCM10 is essential for the initiation of chromosomal DNA replication in Saccharomyces cerevisiae. Mcm10p functionally interacts with components of the pre-replicative complex (Mcm2-Mcm7 complex and origin recognition complex) as well as the pre-initiation complex component (Cdc45p) suggesting that it may be a component of the pre-RC as well as the pre-IC. Two-dimensional gel electrophoresis analysis showed that Mcm10p is required not only for the initiation of DNA synthesis at replication origins but also for the smooth passage of replication forks at origins. Genetic analysis showed that MCM10 interacts with components of the elongation machinery such as Pol delta and Pol epsilon, suggesting that it may play a role in elongation replication. RESULTS We show that the mcm10 mutation causes replication fork pausing not only at potentially active origins but also at silent origins. We screened for mutations that are lethal in combination with mcm10-1 and obtained seven mutants named slm1-slm6 for synthetically lethal with mcm10. These mutants comprised six complementation groups that can be divided into three classes. Class 1 includes genes that encode components of the pre-RC and pre-IC and are represented by SLM3, 4 and 5 which are allelic to MCM7, MCM2 and CDC45, respectively. Class 2 includes genes involved in the processing of Okazaki fragments in lagging strand synthesis and is represented by SLM1, which is allelic to DNA2. Class 3 includes novel DNA repair genes represented by SLM2 and SLM6. CONCLUSIONS The viability of the mcm10-1 mutant is dependent on a novel repair pathway that may participate either in resolving accumulated replication intermediates or the damage caused by blocked replication forks. These results are consistent with the hypothesis that Mcm10p is required for the passage of replication forks through obstacles such as those created by pre-RCs assembled at active or inactive replication origins.
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Affiliation(s)
- Yoshio Araki
- Research Institute for Microbial Diseases, Graduate School of Science, Osaka University, 3-1 Yamada-oka, Suita, Osaka, Japan
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Abstract
Whereas the process of DNA replication is fundamentally conserved in the three domains of life, the archaeal system is closer to that of eukarya than bacteria. In the time since the complete genome sequences of several members of the archaeal domain became available, there has been a burst of research on archaeal DNA replication. These studies have led to both expected and surprising findings. This review summarizes the search for origins of replication in archaea, and our current knowledge of initiation, the process by which replication origins are recognized, the DNA molecule is unwound and the replicative helicase is loaded onto the DNA in preparation for DNA synthesis. The similarities and differences of the initiation process in archea, bacteria and eukarya are also summarized.
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Affiliation(s)
- Lori M Kelman
- Montgomery College, 20200 Observation Drive, Germantown, MD 20876, USA.
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