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Yadav AK, Polasek-Sedlackova H. Quantity and quality of minichromosome maintenance protein complexes couple replication licensing to genome integrity. Commun Biol 2024; 7:167. [PMID: 38336851 PMCID: PMC10858283 DOI: 10.1038/s42003-024-05855-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Accepted: 01/25/2024] [Indexed: 02/12/2024] Open
Abstract
Accurate and complete replication of genetic information is a fundamental process of every cell division. The replication licensing is the first essential step that lays the foundation for error-free genome duplication. During licensing, minichromosome maintenance protein complexes, the molecular motors of DNA replication, are loaded to genomic sites called replication origins. The correct quantity and functioning of licensed origins are necessary to prevent genome instability associated with severe diseases, including cancer. Here, we delve into recent discoveries that shed light on the novel functions of licensed origins, the pathways necessary for their proper maintenance, and their implications for cancer therapies.
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Affiliation(s)
- Anoop Kumar Yadav
- Department of Cell Biology and Epigenetics, Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Hana Polasek-Sedlackova
- Department of Cell Biology and Epigenetics, Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic.
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2
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Bournaka S, Badra-Fajardo N, Arbi M, Taraviras S, Lygerou Z. The cell cycle revisited: DNA replication past S phase preserves genome integrity. Semin Cancer Biol 2024; 99:45-55. [PMID: 38346544 DOI: 10.1016/j.semcancer.2024.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 01/23/2024] [Accepted: 02/05/2024] [Indexed: 02/20/2024]
Abstract
Accurate and complete DNA duplication is critical for maintaining genome integrity. Multiple mechanisms regulate when and where DNA replication takes place, to ensure that the entire genome is duplicated once and only once per cell cycle. Although the bulk of the genome is copied during the S phase of the cell cycle, increasing evidence suggests that parts of the genome are replicated in G2 or mitosis, in a last attempt to secure that daughter cells inherit an accurate copy of parental DNA. Remaining unreplicated gaps may be passed down to progeny and replicated in the next G1 or S phase. These findings challenge the long-established view that genome duplication occurs strictly during the S phase, bridging DNA replication to DNA repair and providing novel therapeutic strategies for cancer treatment.
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Affiliation(s)
- Spyridoula Bournaka
- Department of General Biology, Medical School, University of Patras, Patras 26504, Greece
| | - Nibal Badra-Fajardo
- Department of General Biology, Medical School, University of Patras, Patras 26504, Greece
| | - Marina Arbi
- Department of General Biology, Medical School, University of Patras, Patras 26504, Greece
| | - Stavros Taraviras
- Department of Physiology, Medical School, University of Patras, Patras 26504, Greece
| | - Zoi Lygerou
- Department of General Biology, Medical School, University of Patras, Patras 26504, Greece.
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3
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Williams KS, Secomb TW, El-Kareh AW. An autonomous mathematical model for the mammalian cell cycle. J Theor Biol 2023; 569:111533. [PMID: 37196820 DOI: 10.1016/j.jtbi.2023.111533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 04/04/2023] [Accepted: 05/10/2023] [Indexed: 05/19/2023]
Abstract
A mathematical model for the mammalian cell cycle is developed as a system of 13 coupled nonlinear ordinary differential equations. The variables and interactions included in the model are based on detailed consideration of available experimental data. A novel feature of the model is inclusion of cycle tasks such as origin licensing and initiation, nuclear envelope breakdown and kinetochore attachment, and their interactions with controllers (molecular complexes involved in cycle control). Other key features are that the model is autonomous, except for a dependence on external growth factors; the variables are continuous in time, without instantaneous resets at phase boundaries; mechanisms to prevent rereplication are included; and cycle progression is independent of cell size. Eight variables represent cell cycle controllers: the Cyclin D1-Cdk4/6 complex, APCCdh1, SCFβTrCP, Cdc25A, MPF, NuMA, the securin-separase complex, and separase. Five variables represent task completion, with four for the status of origins and one for kinetochore attachment. The model predicts distinct behaviors corresponding to the main phases of the cell cycle, showing that the principal features of the mammalian cell cycle, including restriction point behavior, can be accounted for in a quantitative mechanistic way based on known interactions among cycle controllers and their coupling to tasks. The model is robust to parameter changes, in that cycling is maintained over at least a five-fold range of each parameter when varied individually. The model is suitable for exploring how extracellular factors affect cell cycle progression, including responses to metabolic conditions and to anti-cancer therapies.
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Affiliation(s)
| | - Timothy W Secomb
- BIO5 Institute, University of Arizona, Tucson, AZ, USA; Department of Physiology, University of Arizona, Tucson, AZ, USA
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4
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Saxena S, Zou L. Hallmarks of DNA replication stress. Mol Cell 2022; 82:2298-2314. [PMID: 35714587 DOI: 10.1016/j.molcel.2022.05.004] [Citation(s) in RCA: 101] [Impact Index Per Article: 50.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 04/15/2022] [Accepted: 05/04/2022] [Indexed: 12/12/2022]
Abstract
Faithful DNA replication is critical for the maintenance of genomic integrity. Although DNA replication machinery is highly accurate, the process of DNA replication is constantly challenged by DNA damage and other intrinsic and extrinsic stresses throughout the genome. A variety of cellular stresses interfering with DNA replication, which are collectively termed replication stress, pose a threat to genomic stability in both normal and cancer cells. To cope with replication stress and maintain genomic stability, cells have evolved a complex network of cellular responses to alleviate and tolerate replication problems. This review will focus on the major sources of replication stress, the impacts of replication stress in cells, and the assays to detect replication stress, offering an overview of the hallmarks of DNA replication stress.
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Affiliation(s)
- Sneha Saxena
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Lee Zou
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA; Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
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5
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Aoun R, El Hadi C, Tahtouh R, El Habre R, Hilal G. Microarray analysis of breast cancer gene expression profiling in response to 2-deoxyglucose, metformin, and glucose starvation. Cancer Cell Int 2022; 22:123. [PMID: 35305635 PMCID: PMC8933915 DOI: 10.1186/s12935-022-02542-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 03/07/2022] [Indexed: 12/24/2022] Open
Abstract
Background Breast cancer (BC) is the most frequently diagnosed cancer in women. Altering glucose metabolism and its effects on cancer progression and treatment resistance is an emerging interest in BC research. For instance, combining chemotherapy with glucose-lowering drugs (2-deoxyglucose (2-DG), metformin (MET)) or glucose starvation (GS) has shown better outcomes than with chemotherapy alone. However, the genes and molecular mechanisms that govern the action of these glucose deprivation conditions have not been fully elucidated. Here, we investigated the differentially expressed genes in MCF-7 and MDA-MB-231 BC cell lines upon treatment with glucose-lowering drugs (2-DG, MET) and GS using microarray analysis to study the difference in biological functions between the glucose challenges and their effect on the vulnerability of BC cells. Methods MDA-MB-231 and MCF-7 cells were treated with 20 mM MET or 4 mM 2-DG for 48 h. GS was performed by gradually decreasing the glucose concentration in the culture medium to 0 g/L, in which the cells remained with fetal bovine serum for one week. Expression profiling was carried out using Affymetrix Human Clariom S microarrays. Differentially expressed genes were obtained from the Transcriptome Analysis Console and enriched using DAVID and R packages. Results Our results showed that MDA-MB-231 cells were more responsive to glucose deprivation than MCF-7 cells. Endoplasmic reticulum stress response and cell cycle inhibition were detected after all three glucose deprivations in MDA-MB-231 cells and only under the metformin and GS conditions in MCF-7 cells. Induction of apoptosis and inhibition of DNA replication were observed with all three treatments in MDA-MB-231 cells and metformin-treated MCF-7 cells. Upregulation of cellular response to reactive oxygen species and inhibition of DNA repair mechanisms resulted after metformin and GS administration in MDA-MB-231 cell lines and metformin-treated MCF-7 cells. Autophagy was induced after 2-DG treatment in MDA-MB-231 cells and after metformin in MCF-7 cells. Finally, inhibition of DNA methylation were observed only with GS in MDA-MB-231 cells. Conclusion The procedure used to process cancer cells and analyze their expression data distinguishes our study from others. GS had the greatest effect on breast cancer cells compared to 2-DG and MET. Combining MET and GS could restrain both cell lines, making them more vulnerable to conventional chemotherapy. Supplementary Information The online version contains supplementary material available at 10.1186/s12935-022-02542-w.
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Rapsomaniki MA, Maxouri S, Nathanailidou P, Garrastacho MR, Giakoumakis NN, Taraviras S, Lygeros J, Lygerou Z. In silico analysis of DNA re-replication across a complete genome reveals cell-to-cell heterogeneity and genome plasticity. NAR Genom Bioinform 2021; 3:lqaa112. [PMID: 33554116 PMCID: PMC7846089 DOI: 10.1093/nargab/lqaa112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 12/15/2020] [Accepted: 01/20/2021] [Indexed: 01/06/2023] Open
Abstract
DNA replication is a complex and remarkably robust process: despite its inherent uncertainty, manifested through stochastic replication timing at a single-cell level, multiple control mechanisms ensure its accurate and timely completion across a population. Disruptions in these mechanisms lead to DNA re-replication, closely connected to genomic instability and oncogenesis. Here, we present a stochastic hybrid model of DNA re-replication that accurately portrays the interplay between discrete dynamics, continuous dynamics and uncertainty. Using experimental data on the fission yeast genome, model simulations show how different regions respond to re-replication and permit insight into the key mechanisms affecting re-replication dynamics. Simulated and experimental population-level profiles exhibit a good correlation along the genome, robust to model parameters, validating our approach. At a single-cell level, copy numbers of individual loci are affected by intrinsic properties of each locus, in cis effects from adjoining loci and in trans effects from distant loci. In silico analysis and single-cell imaging reveal that cell-to-cell heterogeneity is inherent in re-replication and can lead to genome plasticity and a plethora of genotypic variations.
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Affiliation(s)
- Maria Anna Rapsomaniki
- Department of Biology, School of Medicine, University of Patras, 26500 Rio Patras, Greece
| | - Stella Maxouri
- Department of Biology, School of Medicine, University of Patras, 26500 Rio Patras, Greece
| | - Patroula Nathanailidou
- Department of Biology, School of Medicine, University of Patras, 26500 Rio Patras, Greece
| | | | | | - Stavros Taraviras
- Department of Physiology, School of Medicine, University of Patras, 26500 Rio Patras, Greece
| | - John Lygeros
- Automatic Control Laboratory, ETH Zurich, 8092 Zurich, Switzerland
| | - Zoi Lygerou
- Department of Biology, School of Medicine, University of Patras, 26500 Rio Patras, Greece
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Mechanistic insights into KDM4A driven genomic instability. Biochem Soc Trans 2021; 49:93-105. [PMID: 33492339 PMCID: PMC7925003 DOI: 10.1042/bst20191219] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 12/11/2020] [Accepted: 12/15/2020] [Indexed: 12/19/2022]
Abstract
Alterations in global epigenetic signatures on chromatin are well established to contribute to tumor initiation and progression. Chromatin methylation status modulates several key cellular processes that maintain the integrity of the genome. KDM4A, a demethylase that belongs to the Fe-II dependent dioxygenase family that uses α-ketoglutarate and molecular oxygen as cofactors, is overexpressed in several cancers and is associated with an overall poor prognosis. KDM4A demethylates lysine 9 (H3K9me2/3) and lysine 36 (H3K36me3) methyl marks on histone H3. Given the complexity that exists with these marks on chromatin and their effects on transcription and proliferation, it naturally follows that demethylation serves an equally important role in these cellular processes. In this review, we highlight the role of KDM4A in transcriptional modulation, either dependent or independent of its enzymatic activity, arising from the amplification of this demethylase in cancer. KDM4A modulates re-replication of distinct genomic loci, activates cell cycle inducers, and represses proteins involved in checkpoint control giving rise to proliferative damage, mitotic disturbances and chromosomal breaks, ultimately resulting in genomic instability. In parallel, emerging evidence of non-nuclear substrates of epigenetic modulators emphasize the need to investigate the role of KDM4A in regulating non-nuclear substrates and evaluate their contribution to genomic instability in this context. The existence of promising KDM-specific inhibitors makes these demethylases an attractive target for therapeutic intervention in cancers.
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Under-Replicated DNA: The Byproduct of Large Genomes? Cancers (Basel) 2020; 12:cancers12102764. [PMID: 32992928 PMCID: PMC7601121 DOI: 10.3390/cancers12102764] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Revised: 09/21/2020] [Accepted: 09/22/2020] [Indexed: 12/28/2022] Open
Abstract
In this review, we provide an overview of how proliferating eukaryotic cells overcome one of the main threats to genome stability: incomplete genomic DNA replication during S phase. We discuss why it is currently accepted that double fork stalling (DFS) events are unavoidable events in higher eukaryotes with large genomes and which responses have evolved to cope with its main consequence: the presence of under-replicated DNA (UR-DNA) outside S phase. Particular emphasis is placed on the processes that constrain the detrimental effects of UR-DNA. We discuss how mitotic DNA synthesis (MiDAS), mitotic end joining events and 53BP1 nuclear bodies (53BP1-NBs) deal with such specific S phase DNA replication remnants during the subsequent phases of the cell cycle.
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Zhou Y, Pozo PN, Oh S, Stone HM, Cook JG. Distinct and sequential re-replication barriers ensure precise genome duplication. PLoS Genet 2020; 16:e1008988. [PMID: 32841231 PMCID: PMC7473519 DOI: 10.1371/journal.pgen.1008988] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 09/04/2020] [Accepted: 07/12/2020] [Indexed: 01/19/2023] Open
Abstract
Achieving complete and precise genome duplication requires that each genomic segment be replicated only once per cell division cycle. Protecting large eukaryotic genomes from re-replication requires an overlapping set of molecular mechanisms that prevent the first DNA replication step, the DNA loading of MCM helicase complexes to license replication origins, after S phase begins. Previous reports have defined many such origin licensing inhibition mechanisms, but the temporal relationships among them are not clear, particularly with respect to preventing re-replication in G2 and M phases. Using a combination of mutagenesis, biochemistry, and single cell analyses in human cells, we define a new mechanism that prevents re-replication through hyperphosphorylation of the essential MCM loading protein, Cdt1. We demonstrate that Cyclin A/CDK1 can hyperphosphorylate Cdt1 to inhibit MCM re-loading in G2 phase. The mechanism of inhibition is to block Cdt1 binding to MCM independently of other known Cdt1 inactivation mechanisms such as Cdt1 degradation during S phase or Geminin binding. Moreover, our findings suggest that Cdt1 dephosphorylation at the mitosis-to-G1 phase transition re-activates Cdt1. We propose that multiple distinct, non-redundant licensing inhibition mechanisms act in a series of sequential relays through each cell cycle phase to ensure precise genome duplication. The initial step of DNA replication is loading the DNA helicase, MCM, onto DNA during the first phase of the cell division cycle. If MCM loading occurs inappropriately onto DNA that has already been replicated, then cells risk DNA re-replication, a source of endogenous DNA damage and genome instability. How mammalian cells prevent any sections of their very large genomes from re-replicating is still not fully understood. We found that the Cdt1 protein, one of the critical MCM loading factors, is inhibited specifically in late cell cycle stages through a mechanism involving protein phosphorylation. This phosphorylation prevents Cdt1 from binding MCM; when Cdt1 cannot be phosphorylated MCM is inappropriately re-loaded onto DNA and cells are prone to re-replication. When cells divide and transition into G1 phase, Cdt1 is then dephosphorylated to re-activate it for MCM loading. Based on these findings we assert that the different mechanisms that cooperate to avoid re-replication are not redundant. Instead, different cell cycle phases are dominated by different re-replication control mechanisms. These findings have implications for understanding how genomes are duplicated precisely once per cell cycle and shed light on how that process is perturbed by changes in Cdt1 levels or phosphorylation activity.
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Affiliation(s)
- Yizhuo Zhou
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United State of America
| | - Pedro N. Pozo
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United State of America
| | - Seeun Oh
- F. Widjaja Foundation Inflammatory Bowel and Immunobiology Research Institute and the Research Division of Immunology, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, United State of America
| | - Haley M. Stone
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United State of America
| | - Jeanette Gowen Cook
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United State of America
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United State of America
- Lineberger Comprehensive Cancer, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United State of America
- * E-mail:
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10
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Reduced replication origin licensing selectively kills KRAS-mutant colorectal cancer cells via mitotic catastrophe. Cell Death Dis 2020; 11:499. [PMID: 32612138 PMCID: PMC7330027 DOI: 10.1038/s41419-020-2704-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 06/01/2020] [Accepted: 06/08/2020] [Indexed: 12/16/2022]
Abstract
To unravel vulnerabilities of KRAS-mutant CRC cells, a shRNA-based screen specifically inhibiting MAPK pathway components and targets was performed in CaCo2 cells harboring conditional oncogenic KRASG12V. The custom-designed shRNA library comprised 121 selected genes, which were previously identified to be strongly regulated in response to MEK inhibition. The screen showed that CaCo2 cells expressing KRASG12V were sensitive to the suppression of the DNA replication licensing factor minichromosome maintenance complex component 7 (MCM7), whereas KRASwt CaCo2 cells were largely resistant to MCM7 suppression. Similar results were obtained in an isogenic DLD-1 cell culture model. Knockdown of MCM7 in a KRAS-mutant background led to replication stress as indicated by increased nuclear RPA focalization. Further investigation showed a significant increase in mitotic cells after simultaneous MCM7 knockdown and KRASG12V expression. The increased percentage of mitotic cells coincided with strongly increased DNA damage in mitosis. Taken together, the accumulation of DNA damage in mitotic cells is due to replication stress that remained unresolved, which results in mitotic catastrophe and cell death. In summary, the data show a vulnerability of KRAS-mutant cells towards suppression of MCM7 and suggest that inhibiting DNA replication licensing might be a viable strategy to target KRAS-mutant cancers.
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Zhang Y, Li Z, Hao Q, Tan W, Sun J, Li J, Chen CW, Li Z, Meng Y, Zhou Y, Han Z, Pei H, DePamphilis ML, Zhu W. The Cdk2-c-Myc-miR-571 Axis Regulates DNA Replication and Genomic Stability by Targeting Geminin. Cancer Res 2019; 79:4896-4910. [PMID: 31431461 DOI: 10.1158/0008-5472.can-19-0020] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Revised: 04/02/2019] [Accepted: 08/13/2019] [Indexed: 02/07/2023]
Abstract
DNA rereplication leads to genomic instability and has been implicated in the pathology of a variety of human cancers. Eukaryotic DNA replication is tightly controlled to ensure it occurs only once during each cell cycle. Geminin is a critical component of this control, it prevents DNA rereplication from occurring during S, G2, and early M phases by preventing MCM helicases from forming prereplication complexes. Geminin is targeted for degradation by the anaphase-promoting complex (APC/C) from anaphase through G1-phase, however, accumulating evidence indicates that Geminin is downregulated in late S-phase due to an unknown mechanism. Here, we used a high-throughput screen to identify miRNAs that can induce excess DNA replication and found that miR-571 could reduce the protein level of Geminin in late S-phase independent of the APC/C. Furthermore, miR-571 regulated efficient DNA replication and S-phase cell-cycle progression. Strikingly, c-Myc suppressed miR-571 expression by binding directly to the miR-571 promoter. At the beginning of S-phase, Cdk2 phosphorylated c-Myc at Serine 62, promoting its association with the miR-571 promoter region. Collectively, we identify miR-571 as the first miRNA that prevents aberrant DNA replication and the Cdk2-c-Myc-miR-571 axis as a new pathway for regulating DNA replication, cell cycle, and genomic stability in cancer cells. SIGNIFICANCE: These findings identify a novel regulatory mechanism that is critical for maintaining genome integrity by regulating DNA replication and cell-cycle progression.
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Affiliation(s)
- Yi Zhang
- Department of Biochemistry and Molecular Medicine, George Washington University School of Medicine and Health Sciences, Washington, D.C
| | - Zhuqing Li
- Department of Biochemistry and Molecular Medicine, George Washington University School of Medicine and Health Sciences, Washington, D.C
| | - Qiang Hao
- Department of Biochemistry and Molecular Medicine, George Washington University School of Medicine and Health Sciences, Washington, D.C
| | - Wei Tan
- Department of Biochemistry and Molecular Medicine, George Washington University School of Medicine and Health Sciences, Washington, D.C
| | - Jing Sun
- Department of Biochemistry and Molecular Medicine, George Washington University School of Medicine and Health Sciences, Washington, D.C
| | - Jing Li
- Department of Biochemistry and Molecular Medicine, George Washington University School of Medicine and Health Sciences, Washington, D.C
| | - Chi-Wei Chen
- Department of Biochemistry and Molecular Medicine, George Washington University School of Medicine and Health Sciences, Washington, D.C
| | - Zongzhu Li
- Department of Biochemistry and Molecular Medicine, George Washington University School of Medicine and Health Sciences, Washington, D.C
| | - Yunxiao Meng
- Department of Biochemistry and Molecular Medicine, George Washington University School of Medicine and Health Sciences, Washington, D.C
| | - Yuan Zhou
- Department of Biochemistry and Molecular Medicine, George Washington University School of Medicine and Health Sciences, Washington, D.C
| | - Zhiyong Han
- Department of Medical Sciences, Seton Hall-Hackensack Meridian School of Medicine, South Orange, New Jersey
| | - Huadong Pei
- Department of Biochemistry and Molecular Medicine, George Washington University School of Medicine and Health Sciences, Washington, D.C
| | - Melvin L DePamphilis
- National Institute of Child Health and Human Development, NIH, Bethesda, Maryland
| | - Wenge Zhu
- Department of Biochemistry and Molecular Medicine, George Washington University School of Medicine and Health Sciences, Washington, D.C.
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12
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Kim D, Liu Y, Oberly S, Freire R, Smolka MB. ATR-mediated proteome remodeling is a major determinant of homologous recombination capacity in cancer cells. Nucleic Acids Res 2018; 46:8311-8325. [PMID: 30010936 PMCID: PMC6144784 DOI: 10.1093/nar/gky625] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 06/28/2018] [Indexed: 12/20/2022] Open
Abstract
The ATR kinase is crucial for genome maintenance, but the mechanisms by which ATR controls the DNA repair machinery are not fully understood. Here, we find that long-term chronic inhibition of ATR signaling severely impairs the ability of cells to utilize homologous recombination (HR)-mediated DNA repair. Proteomic analysis shows that chronic ATR inhibition depletes the abundance of key HR factors, suggesting that spontaneous ATR signaling enhances the capacity of cells to use HR-mediated repair by controlling the abundance of the HR machinery. Notably, ATR controls the abundance of HR factors largely via CHK1-dependent transcription, and can also promote stabilization of specific HR proteins. Cancer cells exhibit a strong dependency on ATR signaling for maintaining elevated levels of HR factors, and we propose that increased constitutive ATR signaling caused by augmented replication stress in cancer cells drives the enhanced HR capacity observed in certain tumor types. Overall, these findings define a major pro-HR function for ATR and have important implications for therapy by providing rationale for sensitizing HR-proficient cancer cells to PARP inhibitors.
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Affiliation(s)
- Dongsung Kim
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA
| | - Yi Liu
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA
| | - Susannah Oberly
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA
| | - Raimundo Freire
- Unidad de Investigación, Hospital Universitario de Canarias, Instituto de Tecnologias Biomedicas, 38320 Tenerife, Spain
| | - Marcus B Smolka
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA
- To whom correspondence should be addressed. Tel: +1 607 255 0274; Fax: +1 607 255 5961;
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Aucamp J, Bronkhorst AJ, Badenhorst CPS, Pretorius PJ. The diverse origins of circulating cell-free DNA in the human body: a critical re-evaluation of the literature. Biol Rev Camb Philos Soc 2018; 93:1649-1683. [PMID: 29654714 DOI: 10.1111/brv.12413] [Citation(s) in RCA: 184] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 03/06/2018] [Accepted: 03/09/2018] [Indexed: 12/13/2022]
Abstract
Since the detection of cell-free DNA (cfDNA) in human plasma in 1948, it has been investigated as a non-invasive screening tool for many diseases, especially solid tumours and foetal genetic abnormalities. However, to date our lack of knowledge regarding the origin and purpose of cfDNA in a physiological environment has limited its use to more obvious diagnostics, neglecting, for example, its potential utility in the identification of predisposition to disease, earlier detection of cancers, and lifestyle-induced epigenetic changes. Moreover, the concept or mechanism of cfDNA could also have potential therapeutic uses such as in immuno- or gene therapy. This review presents an extensive compilation of the putative origins of cfDNA and then contrasts the contributions of cellular breakdown processes with active mechanisms for the release of cfDNA into the extracellular environment. The involvement of cfDNA derived from both cellular breakdown and active release in lateral information transfer is also discussed. We hope to encourage researchers to adopt a more holistic view of cfDNA research, taking into account all the biological pathways in which cfDNA is involved, and to give serious consideration to the integration of in vitro and in vivo research. We also wish to encourage researchers not to limit their focus to the apoptotic or necrotic fraction of cfDNA, but to investigate the intercellular messaging capabilities of the actively released fraction of cfDNA and to study the role of cfDNA in pathogenesis.
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Affiliation(s)
- Janine Aucamp
- Human Metabolomics, Biochemistry Division, Hoffman Street, North-West University, Private bag X6001 Potchefstroom, 2520, South Africa
| | - Abel J Bronkhorst
- Human Metabolomics, Biochemistry Division, Hoffman Street, North-West University, Private bag X6001 Potchefstroom, 2520, South Africa
| | - Christoffel P S Badenhorst
- Department of Biotechnology and Enzyme Catalysis, Institute of Biochemistry, Greifswald University, Felix-Hausdorff-Straße 4, 17487, Greifswald, Germany
| | - Piet J Pretorius
- Human Metabolomics, Biochemistry Division, Hoffman Street, North-West University, Private bag X6001 Potchefstroom, 2520, South Africa
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14
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Kim GS, Lee I, Kim JH, Hwang DS. The Replication Protein Cdc6 Suppresses Centrosome Over-Duplication in a Manner Independent of Its ATPase Activity. Mol Cells 2017; 40:925-934. [PMID: 29237113 PMCID: PMC5750711 DOI: 10.14348/molcells.2017.0191] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 10/31/2017] [Accepted: 11/07/2017] [Indexed: 11/27/2022] Open
Abstract
The Cdc6 protein is essential for the initiation of chromosomal replication and functions as a licensing factor to maintain chromosome integrity. During the S and G2 phases of the cell cycle, Cdc6 has been found to inhibit the recruitment of pericentriolar material (PCM) proteins to the centrosome and to suppress centrosome over-duplication. In this report, we analyzed the correlation between these two functions of Cdc6 at the centrosome. Cdc6 depletion increased the population of cells showing centrosome over-duplication and premature centrosome separation; Cdc6 expression reversed these changes. Deletion and fusion experiments revealed that the 18 amino acid residues (197-214) of Cdc6, which were fused to the Cdc6-centrosomal localization signal, suppressed centrosome over-duplication and premature centrosome separation. Cdc6 mutant proteins that showed defective ATP binding or hydrolysis did not exhibit a significant difference in suppressing centrosome over-duplication, compared to the wild type protein. In contrast to the Cdc6-mediated inhibition of PCM protein recruitment to the centrosome, the independence of Cdc6 on its ATPase activity for suppressing centrosome over-duplication, along with the difference between the Cdc6 protein regions participating in the two functions, suggested that Cdc6 controls centrosome duplication in a manner independent of its recruitment of PCM proteins to the centrosome.
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Affiliation(s)
- Gwang Su Kim
- Department of Biological Sciences, Seoul National University, Seoul 08826,
Korea
| | - Inyoung Lee
- Department of Biological Sciences, Seoul National University, Seoul 08826,
Korea
| | - Ji Hun Kim
- Department of Biological Sciences, Seoul National University, Seoul 08826,
Korea
| | - Deog Su Hwang
- Department of Biological Sciences, Seoul National University, Seoul 08826,
Korea
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15
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DNA Replication Control During Drosophila Development: Insights into the Onset of S Phase, Replication Initiation, and Fork Progression. Genetics 2017; 207:29-47. [PMID: 28874453 PMCID: PMC5586379 DOI: 10.1534/genetics.115.186627] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 05/19/2017] [Indexed: 12/11/2022] Open
Abstract
Proper control of DNA replication is critical to ensure genomic integrity during cell proliferation. In addition, differential regulation of the DNA replication program during development can change gene copy number to influence cell size and gene expression. Drosophila melanogaster serves as a powerful organism to study the developmental control of DNA replication in various cell cycle contexts in a variety of differentiated cell and tissue types. Additionally, Drosophila has provided several developmentally regulated replication models to dissect the molecular mechanisms that underlie replication-based copy number changes in the genome, which include differential underreplication and gene amplification. Here, we review key findings and our current understanding of the developmental control of DNA replication in the contexts of the archetypal replication program as well as of underreplication and differential gene amplification. We focus on the use of these latter two replication systems to delineate many of the molecular mechanisms that underlie the developmental control of replication initiation and fork elongation.
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16
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Stormo BM, Fox DT. Polyteny: still a giant player in chromosome research. Chromosome Res 2017; 25:201-214. [PMID: 28779272 PMCID: PMC5768140 DOI: 10.1007/s10577-017-9562-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Revised: 07/19/2017] [Accepted: 07/21/2017] [Indexed: 12/17/2022]
Abstract
In this era of high-resolution mapping of chromosome territories, topological interactions, and chromatin states, it is increasingly appreciated that the positioning of chromosomes and their interactions within the nucleus is critical for cellular function. Due to their large size and distinctive structure, polytene chromosomes have contributed a wealth of knowledge regarding chromosome regulation. In this review, we discuss the diversity of polytene chromosomes in nature and in disease, examine the recurring structural features of polytene chromosomes in terms of what they reveal about chromosome biology, and discuss recent advances regarding how polytene chromosomes are assembled and disassembled. After over 130 years of study, these giant chromosomes are still powerful tools to understand chromosome biology.
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Affiliation(s)
- Benjamin M Stormo
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, 27710, USA
| | - Donald T Fox
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, 27710, USA.
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17
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Lee I, Kim GS, Bae JS, Kim J, Rhee K, Hwang DS. The DNA replication protein Cdc6 inhibits the microtubule-organizing activity of the centrosome. J Biol Chem 2017; 292:16267-16276. [PMID: 28827311 DOI: 10.1074/jbc.m116.763680] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 08/14/2017] [Indexed: 11/06/2022] Open
Abstract
The centrosome serves as a major microtubule-organizing center (MTOC). The Cdc6 protein is a component of the pre-replicative complex and a licensing factor for the initiation of chromosome replication and localizes to centrosomes during the S and G2 phases of the cfell cycle of human cells. This cell cycle-dependent localization of Cdc6 to the centrosome motivated us to investigate whether Cdc6 negatively regulates MTOC activity and to determine the integral proteins that comprise the pericentriolar material (PCM). Time-lapse live-cell imaging of microtubule regrowth revealed that Cdc6 depletion increased microtubule nucleation at the centrosomes and that expression of Cdc6 in Cdc6-depleted cells reversed this effect. This increase and decrease in microtubule nucleation correlated with the centrosomal intensities of PCM proteins such as γ-tubulin, pericentrin, CDK5 regulatory subunit-associated protein 2 (CDK5RAP2), and centrosomal protein 192 (Cep192). The regulation of microtubule nucleation and the recruitment of PCM proteins to the centrosome required Cdc6 ATPase activity, as well as a centrosomal localization of Cdc6. These results suggest a novel function for Cdc6 in coordinating centrosome assembly and function.
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Affiliation(s)
- Inyoung Lee
- From the Department of Biological Sciences, Seoul National University, Seoul 08826, Korea
| | - Gwang Su Kim
- From the Department of Biological Sciences, Seoul National University, Seoul 08826, Korea
| | - Jun Sung Bae
- From the Department of Biological Sciences, Seoul National University, Seoul 08826, Korea
| | - Jaeyoun Kim
- From the Department of Biological Sciences, Seoul National University, Seoul 08826, Korea
| | - Kunsoo Rhee
- From the Department of Biological Sciences, Seoul National University, Seoul 08826, Korea
| | - Deog Su Hwang
- From the Department of Biological Sciences, Seoul National University, Seoul 08826, Korea
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18
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Rangaswamy S, Pandey A, Mitra S, Hegde ML. Pre-Replicative Repair of Oxidized Bases Maintains Fidelity in Mammalian Genomes: The Cowcatcher Role of NEIL1 DNA Glycosylase. Genes (Basel) 2017; 8:E175. [PMID: 28665322 PMCID: PMC5541308 DOI: 10.3390/genes8070175] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 06/16/2017] [Accepted: 06/24/2017] [Indexed: 02/06/2023] Open
Abstract
Genomic fidelity in the humans is continuously challenged by genotoxic reactive oxygen species (ROS) generated both endogenously during metabolic processes, and by exogenous agents. Mispairing of most ROS-induced oxidized base lesions during DNA replication induces mutations. Although bulky base adducts induced by ultraviolet light and other environmental mutagens block replicative DNA polymerases, most oxidized base lesions do not block DNA synthesis. In 8-oxo-G:A mispairs generated by the incorporation of A opposite unrepaired 8-oxo-G, A is removed by MutYH (MYH) for post-replicative repair, and other oxidized base lesions must be repaired prior to replication in order to prevent mutation fixation. Our earlier studies documented S phase-specific overexpression of endonuclease VIII-like 1 (NEIL1) DNA glycosylase (DG), one of five oxidized base excision repair (BER)-initiating enzymes in mammalian cells, and its high affinity for replication fork-mimicking single-stranded (ss)DNA substrates. We recently provided experimental evidence for the role of NEIL1 in replicating-strand repair, and proposed the "cowcatcher" model of pre-replicative BER, where NEIL1's nonproductive binding to the lesion base in ssDNA template blocks DNA chain elongation, causing fork regression. Repair of the lesion in the then re-annealed duplex is carried out by NEIL1 in association with the DNA replication proteins. In this commentary, we highlight the critical role of pre-replicative BER in preventing mutagenesis, and discuss the distinction between pre-replicative vs. post-replicative BER.
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Affiliation(s)
- Suganya Rangaswamy
- Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX 77030, USA.
| | - Arvind Pandey
- Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX 77030, USA.
| | - Sankar Mitra
- Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX 77030, USA.
- Weill Cornell Medical College, Cornell University, New York, NY 10065, USA.
| | - Muralidhar L Hegde
- Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX 77030, USA.
- Weill Cornell Medical College, Cornell University, New York, NY 10065, USA.
- Houston Methodist Neurological Institute, Houston, TX 77030, USA.
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19
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Hosogane M, Bosu L, Fukumoto E, Yamada H, Sato S, Nakayama K. Geminin is an indispensable inhibitor of Cdt1 in mouse embryonic stem cells. Genes Cells 2017; 22:360-375. [DOI: 10.1111/gtc.12482] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 01/26/2017] [Indexed: 11/26/2022]
Affiliation(s)
- Masaki Hosogane
- Department of Cell Proliferation, United Center for Advanced Research and Translational Medicine, Graduate School of Medicine; Tohoku University; 2-1 Seiryo-machi, Aoba-ku Sendai Miyagi 980-8575 Japan
| | - Lena Bosu
- Department of Cell Proliferation, United Center for Advanced Research and Translational Medicine, Graduate School of Medicine; Tohoku University; 2-1 Seiryo-machi, Aoba-ku Sendai Miyagi 980-8575 Japan
| | - Emiko Fukumoto
- Department of Cell Proliferation, United Center for Advanced Research and Translational Medicine, Graduate School of Medicine; Tohoku University; 2-1 Seiryo-machi, Aoba-ku Sendai Miyagi 980-8575 Japan
| | - Hidetoshi Yamada
- Department of Cell Proliferation, United Center for Advanced Research and Translational Medicine, Graduate School of Medicine; Tohoku University; 2-1 Seiryo-machi, Aoba-ku Sendai Miyagi 980-8575 Japan
| | - Soichiro Sato
- Department of Cell Proliferation, United Center for Advanced Research and Translational Medicine, Graduate School of Medicine; Tohoku University; 2-1 Seiryo-machi, Aoba-ku Sendai Miyagi 980-8575 Japan
| | - Keiko Nakayama
- Department of Cell Proliferation, United Center for Advanced Research and Translational Medicine, Graduate School of Medicine; Tohoku University; 2-1 Seiryo-machi, Aoba-ku Sendai Miyagi 980-8575 Japan
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20
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Parker MW, Botchan MR, Berger JM. Mechanisms and regulation of DNA replication initiation in eukaryotes. Crit Rev Biochem Mol Biol 2017; 52:107-144. [PMID: 28094588 DOI: 10.1080/10409238.2016.1274717] [Citation(s) in RCA: 117] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Cellular DNA replication is initiated through the action of multiprotein complexes that recognize replication start sites in the chromosome (termed origins) and facilitate duplex DNA melting within these regions. In a typical cell cycle, initiation occurs only once per origin and each round of replication is tightly coupled to cell division. To avoid aberrant origin firing and re-replication, eukaryotes tightly regulate two events in the initiation process: loading of the replicative helicase, MCM2-7, onto chromatin by the origin recognition complex (ORC), and subsequent activation of the helicase by its incorporation into a complex known as the CMG. Recent work has begun to reveal the details of an orchestrated and sequential exchange of initiation factors on DNA that give rise to a replication-competent complex, the replisome. Here, we review the molecular mechanisms that underpin eukaryotic DNA replication initiation - from selecting replication start sites to replicative helicase loading and activation - and describe how these events are often distinctly regulated across different eukaryotic model organisms.
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Affiliation(s)
- Matthew W Parker
- a Department of Biophysics and Biophysical Chemistry , Johns Hopkins University School of Medicine , Baltimore , MD , USA
| | - Michael R Botchan
- b Department of Molecular and Cell Biology , University of California Berkeley , Berkeley , CA , USA
| | - James M Berger
- a Department of Biophysics and Biophysical Chemistry , Johns Hopkins University School of Medicine , Baltimore , MD , USA
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21
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Abstract
As the ratio of the copy number of the most replicated to the unreplicated regions in the same chromosome, the definition of chromosomal replication complexity (CRC) appears to leave little room for variation, being either two during S-phase or one otherwise. However, bacteria dividing faster than they replicate their chromosome spike CRC to four and even eight. A recent experimental inquiry about the limits of CRC in Escherichia coli revealed two major reasons to avoid elevating it further: (i) increased chromosomal fragmentation and (ii) complications with subsequent double-strand break repair. Remarkably, examples of stable elevated CRC in eukaryotic chromosomes are well known under various terms like "differential replication," "underreplication," "DNA puffs," "onion-skin replication," or "re-replication" and highlight the phenomenon of static replication fork (sRF). To accurately describe the resulting "amplification by overinitiation," I propose a new term: "replification" (subchromosomal overreplication). In both prokaryotes and eukaryotes, replification, via sRF processing, causes double-strand DNA breaks and, with their repair elevating chromosomal rearrangements, represents a novel genome instability factor. I suggest how static replication bubbles could be stabilized and speculate that some tandem duplications represent such persistent static bubbles. Moreover, I propose how static replication bubbles could be transformed into tandem duplications, double minutes, or inverted triplications. Possible experimental tests of these models are discussed.
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Affiliation(s)
- Andrei Kuzminov
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- * E-mail:
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22
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Feng W, Michaels SD. Accessing the Inaccessible: The Organization, Transcription, Replication, and Repair of Heterochromatin in Plants. Annu Rev Genet 2016; 49:439-59. [PMID: 26631514 DOI: 10.1146/annurev-genet-112414-055048] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Eukaryotic genomes often contain large quantities of potentially deleterious sequences, such as transposons. One strategy for mitigating this risk is to package such sequences into so-called constitutive heterochromatin, where the dense chromatin environment is thought to inhibit transcription by excluding transcription factors and RNA polymerase. This type of model makes it tempting to think of heterochromatin as an inert region that is isolated from the rest of the nucleus. Recent work on heterochromatin, however, reveals that it is a dynamic environment. Despite its dense packaging, heterochromatin must remain accessible for a host of processes, including DNA replication and repair, and, paradoxically, transcription. In plants, transcripts produced by specialized RNA polymerases are used to target regions of the genome for silencing via DNA methylation. Thus, the maintenance of heterochromatin requires a careful balancing act of access and exclusion, which is achieved through the action of a host of interrelated pathways.
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Affiliation(s)
- Wei Feng
- Carnegie Institution for Science, Department of Plant Biology, Stanford, California 94305;
| | - Scott D Michaels
- Department of Biology, Indiana University, Bloomington, Indiana 47405;
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23
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Lo PK, Lee JS, Liang X, Sukumar S. The dual role of FOXF2 in regulation of DNA replication and the epithelial-mesenchymal transition in breast cancer progression. Cell Signal 2016; 28:1502-19. [PMID: 27377963 DOI: 10.1016/j.cellsig.2016.06.021] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Revised: 06/13/2016] [Accepted: 06/29/2016] [Indexed: 02/06/2023]
Abstract
Dysregulation of Forkhead-box (FOX) transcription factors is linked to cancers of numerous tissue types. Here, we report that FOXF2 is frequently silenced in luminal-type and HER2-positive breast cancers, but is overexpressed in basal-like breast cancers; thus, FOXF2 appears to play distinct roles in different breast cancer subtypes. Inactivation of FOXF2 in luminal-type and HER2-positive breast cancers is attributable to epigenetic silencing. Silencing of FOXF2 is associated with poor prognosis in luminal-type breast cancer. Ectopic expression of FOXF2 in luminal and HER2-positive breast cancer cells suppresses their tumorigenic properties in vitro and in vivo via inhibition of the CDK2-RB-E2F cascade. The in vivo function of FOXF2 is to maintain the stringency of DNA replication, and its loss triggers dysregulation of DNA replication, which in turn activates the p53 checkpoint pathway. Besides its role in cell cycle regulation, FOXF2 is functionally required for mobility and epithelial-to-mesenchymal transition (EMT) of normal breast epithelial cells. In basal-like breast cancer cells, the cell-cycle function of FOXF2 is impaired. However, the EMT function of FOXF2 is still required for mobility, invasiveness and anchorage-independent growth of basal-like breast cancer cells. Our gene expression profiling studies demonstrate that FOXF2 regulates the expression of genes implicated in cell cycle and EMT regulation. Moreover, FOXF2 is highly co-expressed with basal- and metastasis-related genes in breast cancer. These findings suggest that FOXF2 has a dual role in breast tumorigenesis and functions as either a tumor suppressor or an oncogene depending on the breast tumor subtype.
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Affiliation(s)
- Pang-Kuo Lo
- Breast Cancer Program, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| | - Ji Shin Lee
- Breast Cancer Program, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Xiaohui Liang
- Breast Cancer Program, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Saraswati Sukumar
- Breast Cancer Program, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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24
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Plasma membrane/cell wall perturbation activates a novel cell cycle checkpoint during G1 in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 2016; 113:6910-5. [PMID: 27274080 DOI: 10.1073/pnas.1523824113] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Cellular wound healing or the repair of plasma membrane/cell wall damage (plasma membrane damage) occurs frequently in nature. Although various cellular perturbations, such as DNA damage, spindle misalignment, and impaired daughter cell formation, are monitored by cell cycle checkpoint mechanisms in budding yeast, whether plasma membrane damage is monitored by any of these checkpoints remains to be addressed. Here, we define the mechanism by which cells sense membrane damage and inhibit DNA replication. We found that the inhibition of DNA replication upon plasma membrane damage requires GSK3/Mck1-dependent degradation of Cdc6, a component of the prereplicative complex. Furthermore, the CDK inhibitor Sic1 is stabilized in response to plasma membrane damage, leading to cell integrity maintenance in parallel with the Mck1-Cdc6 pathway. Cells defective in both Cdc6 degradation and Sic1 stabilization failed to grow in the presence of plasma membrane damage. Taking these data together, we propose that plasma membrane damage triggers G1 arrest via Cdc6 degradation and Sic1 stabilization to promote the cellular wound healing process.
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25
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Abstract
Size and shape are important aspects of nuclear structure. While normal cells maintain nuclear size within a defined range, altered nuclear size and shape are associated with a variety of diseases. It is unknown if altered nuclear morphology contributes to pathology, and answering this question requires a better understanding of the mechanisms that control nuclear size and shape. In this review, we discuss recent advances in our understanding of the mechanisms that regulate nuclear morphology, focusing on nucleocytoplasmic transport, nuclear lamins, the endoplasmic reticulum, the cell cycle, and potential links between nuclear size and size regulation of other organelles. We then discuss the functional significance of nuclear morphology in the context of early embryonic development. Looking toward the future, we review new experimental approaches that promise to provide new insights into mechanisms of nuclear size control, in particular microfluidic-based technologies, and discuss how altered nuclear morphology might impact chromatin organization and physiology of diseased cells.
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Affiliation(s)
- Richik N Mukherjee
- a Department of Molecular Biology , University of Wyoming , Laramie , WY USA
| | - Pan Chen
- a Department of Molecular Biology , University of Wyoming , Laramie , WY USA
| | - Daniel L Levy
- a Department of Molecular Biology , University of Wyoming , Laramie , WY USA
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26
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Khan SR, Mahaseth T, Kouzminova EA, Cronan GE, Kuzminov A. Static and Dynamic Factors Limit Chromosomal Replication Complexity in Escherichia coli, Avoiding Dangers of Runaway Overreplication. Genetics 2016; 202:945-60. [PMID: 26801182 PMCID: PMC4788131 DOI: 10.1534/genetics.115.184697] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Accepted: 01/17/2016] [Indexed: 12/21/2022] Open
Abstract
We define chromosomal replication complexity (CRC) as the ratio of the copy number of the most replicated regions to that of unreplicated regions on the same chromosome. Although a typical CRC of eukaryotic or bacterial chromosomes is 2, rapidly growing Escherichia coli cells induce an extra round of replication in their chromosomes (CRC = 4). There are also E. coli mutants with stable CRC∼6. We have investigated the limits and consequences of elevated CRC in E. coli and found three limits: the "natural" CRC limit of ∼8 (cells divide more slowly); the "functional" CRC limit of ∼22 (cells divide extremely slowly); and the "tolerance" CRC limit of ∼64 (cells stop dividing). While the natural limit is likely maintained by the eclipse system spacing replication initiations, the functional limit might reflect the capacity of the chromosome segregation system, rather than dedicated mechanisms, and the tolerance limit may result from titration of limiting replication factors. Whereas recombinational repair is beneficial for cells at the natural and functional CRC limits, we show that it becomes detrimental at the tolerance CRC limit, suggesting recombinational misrepair during the runaway overreplication and giving a rationale for avoidance of the latter.
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Affiliation(s)
- Sharik R Khan
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Tulip Mahaseth
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Elena A Kouzminova
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Glen E Cronan
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Andrei Kuzminov
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
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27
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Karavias D, Maroulis I, Papadaki H, Gogos C, Kakkos S, Karavias D, Bravou V. Overexpression of CDT1 Is a Predictor of Poor Survival in Patients with Hepatocellular Carcinoma. J Gastrointest Surg 2016; 20:568-79. [PMID: 26408331 DOI: 10.1007/s11605-015-2960-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 09/16/2015] [Indexed: 01/31/2023]
Abstract
BACKGROUND Genomic instability is a common feature in hepatocellular carcinoma. Deregulation of replication licensing factors has been shown to trigger DNA damage response contributing to genomic instability. Overexpression of DNA replication licensing factors chromatin licensing and DNA replication factor 1 (CDT1) and minichromosome maintenance complex component 7 (MCM7) has been previously reported in several human cancers. The aim of the present study was to evaluate the expression and prognostic significance of CDT1 and MCM7 in association with DNA damage response markers and p53 in patients with hepatocellular carcinoma. METHODS Expression of CDT1, MCM7, p-H2A histone family member X (H2AX), phospho-ataxia telangiectasia-mutated (ATM)/ataxia telangiectasia rad3-related (ATR) substrate, and p53 was evaluated by immunohistochemistry on formalin-fixed paraffin-embedded surgical specimens from 111 patients who underwent hepatectomy for hepatocellular carcinoma. Statistical analysis was performed to evaluate associations between the studied proteins, clinicopathological parameters, and patient survival. RESULTS CDT1 expression correlated with p-H2AX (p = 0.038), while MCM7 correlated with p-H2AX and phospho-ATM/ATR substrate (p < 0.001). Increased CDT1 expression was associated with higher tumor grade (p = 0.006) and tumor-node-metastasis (TNM) stage (p = 0.033). High CDT1 expression correlated significantly with reduced overall survival (60.8 and 26.5 % vs 82.8 and 53.0 %, for low CDT1 expression, at 2 and 5 years, respectively, p = 0.012) and was identified by multivariate analysis as an independent predictor of poor overall survival (p = 0.049). CONCLUSIONS Overexpression of CDT1 and MCM7 in hepatocellular carcinoma correlates with DNA damage response, and CDT1 overexpression is a significant prognostic biomarker in hepatocellular carcinoma.
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Affiliation(s)
- Dimitrios Karavias
- Department of Surgery, University Hospital of Patras, Rio, 26500, Greece.
| | - Ioannis Maroulis
- Department of Surgery, University Hospital of Patras, Rio, 26500, Greece
| | - Helen Papadaki
- Department of Anatomy, Histology and Embryology, School of Medicine, University of Patras, Rio, Greece
| | - Charalambos Gogos
- Department of Internal Medicine, University Hospital of Patras, Rio, Greece
| | - Stavros Kakkos
- Department of Vascular Surgery, University Hospital of Patras, Rio, Greece
| | | | - Vasiliki Bravou
- Department of Anatomy, Histology and Embryology, School of Medicine, University of Patras, Rio, Greece
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28
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D'Assoro AB, Haddad T, Galanis E. Aurora-A Kinase as a Promising Therapeutic Target in Cancer. Front Oncol 2016; 5:295. [PMID: 26779440 PMCID: PMC4701905 DOI: 10.3389/fonc.2015.00295] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 12/11/2015] [Indexed: 12/14/2022] Open
Abstract
Mammalian Aurora family of serine/threonine kinases are master regulators of mitotic progression and are frequently overexpressed in human cancers. Among the three members of the Aurora kinase family (Aurora-A, -B, and -C), Aurora-A and Aurora-B are expressed at detectable levels in somatic cells undergoing mitotic cell division. Aberrant Aurora-A kinase activity has been implicated in oncogenic transformation through the development of chromosomal instability and tumor cell heterogeneity. Recent studies also reveal a novel non-mitotic role of Aurora-A activity in promoting tumor progression through activation of epithelial-mesenchymal transition reprograming resulting in the genesis of tumor-initiating cells. Therefore, Aurora-A kinase represents an attractive target for cancer therapeutics, and the development of small molecule inhibitors of Aurora-A oncogenic activity may improve the clinical outcomes of cancer patients. In the present review, we will discuss mitotic and non-mitotic functions of Aurora-A activity in oncogenic transformation and tumor progression. We will also review the current clinical studies, evaluating small molecule inhibitors of Aurora-A activity and their efficacy in the management of cancer patients.
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Affiliation(s)
- Antonino B D'Assoro
- Department of Medical Oncology, Mayo Clinic College of Medicine, Rochester, MN, USA; Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, MN, USA
| | - Tufia Haddad
- Department of Medical Oncology, Mayo Clinic College of Medicine , Rochester, MN , USA
| | - Evanthia Galanis
- Department of Medical Oncology, Mayo Clinic College of Medicine, Rochester, MN, USA; Department of Molecular Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA
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29
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Hutchins JRA, Aze A, Coulombe P, Méchali M. Characteristics of Metazoan DNA Replication Origins. DNA REPLICATION, RECOMBINATION, AND REPAIR 2016. [PMCID: PMC7120227 DOI: 10.1007/978-4-431-55873-6_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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30
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Hesketh EL, Knight JRP, Wilson RHC, Chong JPJ, Coverley D. Transient association of MCM complex proteins with the nuclear matrix during initiation of mammalian DNA replication. Cell Cycle 2015; 14:333-41. [PMID: 25659032 DOI: 10.4161/15384101.2014.980647] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The minichromosome maintenance complex (MCM2-7) is the putative DNA helicase in eukaryotes, and essential for DNA replication. By applying serial extractions to mammalian cells synchronized by release from quiescence, we reveal dynamic changes to the sub-nuclear compartmentalization of MCM2 as cells pass through late G1 and early S phase, identifying a brief window when MCM2 becomes transiently attached to the nuclear-matrix. The data distinguish 3 states that correspond to loose association with chromatin prior to DNA replication, transient highly stable binding to the nuclear-matrix coincident with initiation, and a post-initiation phase when MCM2 remains tightly associated with chromatin but not the nuclear-matrix. The data suggests that functional MCM complex loading takes place at the nuclear-matrix.
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Affiliation(s)
- Emma L Hesketh
- a Department of Biology ; University of York ; York , UK
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31
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Olivero M, Dettori D, Arena S, Zecchin D, Lantelme E, Di Renzo MF. The stress phenotype makes cancer cells addicted to CDT2, a substrate receptor of the CRL4 ubiquitin ligase. Oncotarget 2015; 5:5992-6002. [PMID: 25115388 PMCID: PMC4171607 DOI: 10.18632/oncotarget.2042] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
CDT2/L2DTL/RAMP is one of the substrate receptors of the Cullin Ring Ubiquitin Ligase 4 that targets for ubiquitin mediated degradation a number of substrates, such as CDT1, p21 and CHK1, involved in the regulation of cell cycle and survival. Here we show that CDT2 depletion was alone able to induce the apoptotic death in 12/12 human cancer cell lines from different tissues, regardless of the mutation profile and CDT2 expression level. Cell death was associated to rereplication and to loss of CDT1 degradation. Conversely, CDT2 depletion did not affect non-transformed human cells, such as immortalized kidney, lung and breast cell lines, and primary cultures of endothelial cells and osteoblasts. The ectopic over-expression of an activated oncogene, such as the mutation-activated RAS or the amplified MET in non-transformed immortalized breast cell lines and primary human osteoblasts, respectively, made cells transformed in vitro, tumorigenic in vivo, and susceptible to CDT2 loss. The widespread effect of CDT2 depletion in different cancer cells suggests that CDT2 is not in a synthetic lethal interaction to a single specific pathway. CDT2 likely is a non-oncogene to which transformed cells become addicted because of their enhanced cellular stress, such as replicative stress and DNA damage.
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Affiliation(s)
- Martina Olivero
- Department of Oncology, University of Torino, Candiolo, Torino, Italy; Candiolo Cancer Institute - FPO IRCCS, Candiolo, Torino, Italy
| | - Daniela Dettori
- Department of Oncology, University of Torino, Candiolo, Torino, Italy; Candiolo Cancer Institute - FPO IRCCS, Candiolo, Torino, Italy; present address: HUGEF, Human Genetics Foundation, Torino, Italy
| | - Sabrina Arena
- Department of Oncology, University of Torino, Candiolo, Torino, Italy; Candiolo Cancer Institute - FPO IRCCS, Candiolo, Torino, Italy
| | - Davide Zecchin
- Department of Oncology, University of Torino, Candiolo, Torino, Italy; Candiolo Cancer Institute - FPO IRCCS, Candiolo, Torino, Italy; present address: Signal Transduction Laboratory, Cancer Research UK London Research Institute, London U.K
| | - Erica Lantelme
- Department of Oncology, University of Torino, Candiolo, Torino, Italy; Candiolo Cancer Institute - FPO IRCCS, Candiolo, Torino, Italy; present address: Washington University in St. Louis, St. Louis, MO
| | - Maria Flavia Di Renzo
- Department of Oncology, University of Torino, Candiolo, Torino, Italy; Candiolo Cancer Institute - FPO IRCCS, Candiolo, Torino, Italy
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32
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Dewar JM, Budzowska M, Walter JC. The mechanism of DNA replication termination in vertebrates. Nature 2015; 525:345-50. [PMID: 26322582 PMCID: PMC4575634 DOI: 10.1038/nature14887] [Citation(s) in RCA: 107] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2014] [Accepted: 07/01/2015] [Indexed: 12/18/2022]
Abstract
Eukaryotic DNA replication terminates when replisomes from adjacent replication origins converge. Termination involves local completion of DNA synthesis, decatenation of daughter molecules, and replisome disassembly. Termination has been difficult to study because termination events are generally asynchronous and sequence non-specific. To overcome these challenges, we paused converging replisomes with a site-specific barrier in Xenopus egg extracts. Upon removal of the barrier, forks underwent synchronous and site-specific termination, allowing mechanistic dissection of this process. We show that DNA synthesis does not slow detectably as forks approach each other and that leading strands pass each other unhindered before undergoing ligation to downstream lagging strands. Dissociation of CMG helicases occurs only after the final ligation step, and is not required for completion of DNA synthesis, strongly suggesting that converging CMGs pass one another and dissociate from double-stranded DNA. This termination mechanism allows rapid completion of DNA synthesis while avoiding premature replisome disassembly
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Affiliation(s)
- James M Dewar
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Magda Budzowska
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Johannes C Walter
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.,Howard Hughes Medical Institute, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
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33
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Abstract
Black et al. demonstrate that hypoxia induces transient, site-specific copy gains in primary, nontransformed, and transformed human cells. Hypoxia-driven copy gains are dependent on the KDM4A histone demethylase and are blocked by inhibition of KDM4A with a small molecule or the natural metabolite succinate. Copy number heterogeneity is a prominent feature within tumors. The molecular basis for this heterogeneity remains poorly characterized. Here, we demonstrate that hypoxia induces transient site-specific copy gains (TSSGs) in primary, nontransformed, and transformed human cells. Hypoxia-driven copy gains are not dependent on HIF1α or HIF2α; however, they are dependent on the KDM4A histone demethylase and are blocked by inhibition of KDM4A with a small molecule or the natural metabolite succinate. Furthermore, this response is conserved at a syntenic region in zebrafish cells. Regions with site-specific copy gain are also enriched for amplifications in hypoxic primary tumors. These tumors exhibited amplification and overexpression of the drug resistance gene CKS1B, which we recapitulated in hypoxic breast cancer cells. Our results demonstrate that hypoxia provides a biological stimulus to create transient site-specific copy alterations that could result in heterogeneity within tumors and cell populations. These findings have major implications in our understanding of copy number heterogeneity and the emergence of drug resistance genes in cancer.
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34
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Kuku S, Proctor I, Loddo M, Kadalayil L, KhoshZaban M, Ledermann J, McCormack M. Do Cell-Cycle Phase-Specific Markers Predict Disease Grade, Stage, and Outcome in Cervical Carcinoma? Int J Gynecol Cancer 2015; 25:1066-72. [PMID: 25621411 DOI: 10.1097/igc.0000000000000356] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
AIMS Multiparameter analysis of cell cycle markers has shown a strong relationship between cell cycle progression and tumor grade, stage, and clinical outcome in penile, renal, ovarian, and breast cancers. We sought to link expression of cell cycle phase-specific markers in cervical cancer to tumor grade, stage, and clinical outcome to investigate their potential use as prognostic and predictive markers. METHODS Pretreatment biopsy material was obtained from 35 patients with cervical cancer (stage IB2-IVA) and 12 normal cervix control cases. Each patient was treated with neoadjuvant chemotherapy followed by chemoradiation. Immunohistochemical staining was performed using a panel of cell cycle phase markers: replication licensing factors: Mcm2 (minichromosome maintenance 2) and geminin, and the standard proliferation marker Ki67 (clone MIB-1). RESULTS The expression levels of each cell cycle biomarker were very high in all cases of squamous cell carcinoma of the cervix regardless of grade or stage of disease. In our cohort, all cases displayed an aggressive, so-called actively cycling phenotype. Univariate analysis showed that none of the cell cycle biomarkers predicted grade, stage, or clinical outcome. CONCLUSIONS Cell cycle phase-specific markers do not appear to predict disease grade, stage, or outcome in our sample of patients with cervical cancer. This is not surprising, given that the expression of each cell cycle biomarker was very high in all cases.Indeed, all the cases of squamous cell carcinoma of the cervix (n = 28) and all but 1 of the adenocarcinomas (n = 7) in this study displayed an aggressive "actively cycling" phenotype. This predominance of actively cycling tumors is unusual and may reflect the viral etiology underlying the disease. These preliminary findings raise many interesting questions including the prognostic value of disease grade and markers of proliferation in cervical tumors as reliable prognostic indicators. Further work on a larger cohort of patients is warranted.
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Affiliation(s)
- Stephanie Kuku
- *Department of Oncology, †Department of Pathology and Wolfson Institute for Biomedical Research, UCL Cancer Institute, and ‡Cancer Trials Center, University College London, London, United Kingdom
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35
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Gerhardt J, Guler GD, Fanning E. Human DNA helicase B interacts with the replication initiation protein Cdc45 and facilitates Cdc45 binding onto chromatin. Exp Cell Res 2015; 334:283-93. [PMID: 25933514 DOI: 10.1016/j.yexcr.2015.04.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2015] [Revised: 04/17/2015] [Accepted: 04/20/2015] [Indexed: 10/23/2022]
Abstract
The chromosomal DNA replication in eukaryotic cells begins at replication initation sites, which are marked by the assembly of the pre-replication complexes in early G1. At the G1/S transition, recruitment of additional replication initiation proteins enables origin DNA unwinding and loading of DNA polymerases. We found that depletion of the human DNA helicase B (HDHB) inhibits the initiation of DNA replication, suggesting a role of HDHB in the beginning of the DNA synthesis. To gain insight into the function of HDHB during replication initiation, we examined the physical interactions of purified recombinant HDHB with key initiation proteins. HDHB interacts directly with two initiation factors TopBP1 and Cdc45. In addition we found that both, the N-terminus and helicase domain of HDHB bind to the N-terminus of Cdc45. Furthermore depletion of HDHB from human cells diminishes Cdc45 association with chromatin, suggesting that HDHB may facilitate Cdc45 recruitment at G1/S in human cells.
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Affiliation(s)
- Jeannine Gerhardt
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Gulfem D Guler
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA
| | - Ellen Fanning
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA
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36
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Re-replication of a centromere induces chromosomal instability and aneuploidy. PLoS Genet 2015; 11:e1005039. [PMID: 25901968 PMCID: PMC4406714 DOI: 10.1371/journal.pgen.1005039] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 01/28/2015] [Indexed: 12/19/2022] Open
Abstract
The faithful inheritance of chromosomes during cell division requires their precise replication and segregation. Numerous mechanisms ensure that each of these fundamental cell cycle events is performed with a high degree of fidelity. The fidelity of chromosomal replication is maintained in part by re-replication controls that ensure there are no more than two copies of every genomic segment to distribute to the two daughter cells. This control is enforced by inhibiting replication initiation proteins from reinitiating replication origins within a single cell cycle. Here we show in Saccharomyces cerevisiae that re-replication control is important for the fidelity of chromosome segregation. In particular, we demonstrate that transient re-replication of centromeric DNA due to disruption of re-replication control greatly induces aneuploidy of the re-replicated chromosome. Some of this aneuploidy arises from missegregation of both sister chromatids to one daughter cell. Aneuploidy can also arise from the generation of an extra sister chromatid via homologous recombination, suggesting that centromeric re-replication can trigger breakage and repair events that expand chromosome number without causing chromosomal rearrangements. Thus, we have identified a potential new non-mitotic source of aneuploidy that can arise from a defect in re-replication control. Given the emerging connections between the deregulation of replication initiation proteins and oncogenesis, this finding may be relevant to the aneuploidy that is prevalent in cancer. The stable inheritance of genetic information requires an elaborate mitotic machinery that acts on the centromeres of chromosomes to ensure their precise segregation. Errors in this segregation can lead to aneuploidy, an unbalanced chromosomal state in which some chromosomes have different copy number than others. Because aneuploidy is associated with developmental abnormalities and diseases such as cancer, there is considerable interest in understanding how these segregation errors arise. Much of this interest has focused on identifying defects in proteins that make up the mitotic machinery. Here, we show that defects in a completely separate process, the control of DNA replication initiation, can lead to chromosome segregation errors as a result of inappropriate re-replication of centromeres. Similar deregulation of replication initiation proteins has been observed in primary human tumors and shown to promote oncogenesis in mouse models. Together, these results raise the possibility that centromeric re-replication may be an additional source of aneuploidy in cancer. In combination with our previous work showing that re-replication is a potent inducer of gene amplification, these results also highlight the versatility of re-replication as a source of genomic instability.
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37
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Environmental stress induces trinucleotide repeat mutagenesis in human cells. Proc Natl Acad Sci U S A 2015; 112:3764-9. [PMID: 25775519 DOI: 10.1073/pnas.1421917112] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The dynamic mutability of microsatellite repeats is implicated in the modification of gene function and disease phenotype. Studies of the enhanced instability of long trinucleotide repeats (TNRs)-the cause of multiple human diseases-have revealed a remarkable complexity of mutagenic mechanisms. Here, we show that cold, heat, hypoxic, and oxidative stresses induce mutagenesis of a long CAG repeat tract in human cells. We show that stress-response factors mediate the stress-induced mutagenesis (SIM) of CAG repeats. We show further that SIM of CAG repeats does not involve mismatch repair, nucleotide excision repair, or transcription, processes that are known to promote TNR mutagenesis in other pathways of instability. Instead, we find that these stresses stimulate DNA rereplication, increasing the proportion of cells with >4 C-value (C) DNA content. Knockdown of the replication origin-licensing factor CDT1 eliminates both stress-induced rereplication and CAG repeat mutagenesis. In addition, direct induction of rereplication in the absence of stress also increases the proportion of cells with >4C DNA content and promotes repeat mutagenesis. Thus, environmental stress triggers a unique pathway for TNR mutagenesis that likely is mediated by DNA rereplication. This pathway may impact normal cells as they encounter stresses in their environment or during development or abnormal cells as they evolve metastatic potential.
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38
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Dellino GI, Pelicci PG. Next-generation sequencing and DNA replication in human cells: the future has arrived. Future Oncol 2015; 10:683-93. [PMID: 24754597 DOI: 10.2217/fon.13.182] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Accurate regulation of DNA replication ensures faithful transmission of eukaryotic genomes and maintenance of genomic stability and chromatin organization. However, by itself the replication process is a threat for both DNA and chromatin integrity. This becomes particularly relevant in cancer cells, where activated oncogenes induce replication-stress, including unscheduled initiation, fork stalling and collapse and, ultimately, genomic instability. Studies addressing the relationship between (epi)genome integrity and disease have been hampered by our poor knowledge of the mechanisms regulating where and when eukaryotic replication initiates. Recently developed genome-scale methods for the analysis of DNA replication in mammals will contribute to the identification of missing links between replication, chromatin regulation and genome stability in normal and cancer cells.
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Affiliation(s)
- Gaetano Ivan Dellino
- Department of Experimental Oncology, European Institute of Oncology, 20141 Milan, Italy
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39
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Kim GS, Kang J, Bang SW, Hwang DS. Cdc6 localizes to S- and G2-phase centrosomes in a cell cycle-dependent manner. Biochem Biophys Res Commun 2014; 456:763-7. [PMID: 25498505 DOI: 10.1016/j.bbrc.2014.12.018] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 12/04/2014] [Indexed: 12/24/2022]
Abstract
The Cdc6 protein has been primarily investigated as a component of the pre-replicative complex for the initiation of chromosome replication, which contributes to maintenance of chromosomal integrity. Here, we show that Cdc6 localized to the centrosomes during S and G2 phases of the cell cycle. The centrosomal localization was mediated by Cdc6 amino acid residues 311-366, which are conserved within other Cdc6 homologues and contains a putative nuclear export signal. Deletions or substitutions of the amino acid residues did not allow the proteins to localize to centrosomes. In contrast, DsRed tag fused to the amino acid residues localized to centrosomes. These results indicated that a centrosome localization signal is contained within amino acid residues 311-366. The cell cycle-dependent centrosomal localization of Cdc6 in S and G2 phases suggest a novel function of Cdc6 in centrosomes.
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Affiliation(s)
- Gwang Su Kim
- Department of Biological Sciences, Seoul National University, Seoul 151-742, Republic of Korea
| | - Jeeheon Kang
- Department of Biological Sciences, Seoul National University, Seoul 151-742, Republic of Korea
| | - Sung Woong Bang
- Department of Biological Sciences, Seoul National University, Seoul 151-742, Republic of Korea
| | - Deog Su Hwang
- Department of Biological Sciences, Seoul National University, Seoul 151-742, Republic of Korea.
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40
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Both high-fidelity replicative and low-fidelity Y-family polymerases are involved in DNA rereplication. Mol Cell Biol 2014; 35:699-715. [PMID: 25487575 DOI: 10.1128/mcb.01153-14] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
DNA rereplication is a major form of aberrant replication that causes genomic instabilities, such as gene amplification. However, little is known about which DNA polymerases are involved in the process. Here, we report that low-fidelity Y-family polymerases (Y-Pols), Pol η, Pol ι, Pol κ, and REV1, significantly contribute to DNA synthesis during rereplication, while the replicative polymerases, Pol δ and Pol ε, play an important role in rereplication, as expected. When rereplication was induced by depletion of geminin, these polymerases were recruited to rereplication sites in human cell lines. This finding was supported by RNA interference (RNAi)-mediated knockdown of the polymerases, which suppressed rereplication induced by geminin depletion. Interestingly, epistatic analysis indicated that Y-Pols collaborate in a common pathway, independently of replicative polymerases. We also provide evidence for a catalytic role for Pol η and the involvement of Pol η and Pol κ in cyclin E-induced rereplication. Collectively, our findings indicate that, unlike normal S-phase replication, rereplication induced by geminin depletion and oncogene activation requires significant contributions of both Y-Pols and replicative polymerases. These findings offer important mechanistic insights into cancer genomic instability.
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41
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Zhang J, Zuo T, Wang D, Peterson T. Transposition-mediated DNA re-replication in maize. eLife 2014; 3:e03724. [PMID: 25406063 PMCID: PMC4270019 DOI: 10.7554/elife.03724] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 11/17/2014] [Indexed: 02/03/2023] Open
Abstract
Every DNA segment in a eukaryotic genome normally replicates once and only once per cell cycle to maintain genome stability. We show here that this restriction can be bypassed through alternative transposition, a transposition reaction that utilizes the termini of two separate, nearby transposable elements (TEs). Our results suggest that alternative transposition during S phase can induce re-replication of the TEs and their flanking sequences. The DNA re-replication can spontaneously abort to generate double-strand breaks, which can be repaired to generate Composite Insertions composed of transposon termini flanking segmental duplications of various lengths. These results show how alternative transposition coupled with DNA replication and repair can significantly alter genome structure and may have contributed to rapid genome evolution in maize and possibly other eukaryotes.
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Affiliation(s)
- Jianbo Zhang
- Department of Genetics,
Development and Cell Biology, Iowa State
University, Ames, United States
- Department of
Agronomy, Iowa State University,
Ames,
United States
| | - Tao Zuo
- Department of Genetics,
Development and Cell Biology, Iowa State
University, Ames, United States
- Department of
Agronomy, Iowa State University,
Ames,
United States
| | - Dafang Wang
- Department of Genetics,
Development and Cell Biology, Iowa State
University, Ames, United States
- Department of
Agronomy, Iowa State University,
Ames,
United States
| | - Thomas Peterson
- Department of Genetics,
Development and Cell Biology, Iowa State
University, Ames, United States
- Department of
Agronomy, Iowa State University,
Ames,
United States
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42
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McCann MJ, Rowland IR, Roy NC. The anti-proliferative effects of enterolactone in prostate cancer cells: evidence for the role of DNA licencing genes, mi-R106b cluster expression, and PTEN dosage. Nutrients 2014; 6:4839-55. [PMID: 25372501 PMCID: PMC4245566 DOI: 10.3390/nu6114839] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Revised: 10/10/2014] [Accepted: 10/20/2014] [Indexed: 01/20/2023] Open
Abstract
The mammalian lignan, enterolactone, has been shown to reduce the proliferation of the earlier stages of prostate cancer at physiological concentrations in vitro. However, efficacy in the later stages of the disease occurs at concentrations difficult to achieve through dietary modification. We have therefore investigated what concentration(s) of enterolactone can restrict proliferation in multiple stages of prostate cancer using an in vitro model system of prostate disease. We determined that enterolactone at 20 μM significantly restricted the proliferation of mid and late stage models of prostate disease. These effects were strongly associated with changes in the expression of the DNA licencing genes (GMNN, CDT1, MCM2 and 7), in reduced expression of the miR-106b cluster (miR-106b, miR-93, and miR-25), and in increased expression of the PTEN tumour suppressor gene. We have shown anti-proliferative effects of enterolactone in earlier stages of prostate disease than previously reported and that these effects are mediated, in part, by microRNA-mediated regulation.
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Affiliation(s)
- Mark J McCann
- Food Nutrition & Health, Food and Bio-based Products, AgResearch Grasslands Research Centre, Palmerston North 4442, New Zealand.
| | - Ian R Rowland
- Department of Food and Nutritional Sciences, P.O. Box 226, Whiteknights, Reading RG6 6AP, UK.
| | - Nicole C Roy
- Food Nutrition & Health, Food and Bio-based Products, AgResearch Grasslands Research Centre, Palmerston North 4442, New Zealand.
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43
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Chao TC, Chen KJ, Tang MC, Chan LC, Chen PM, Tzeng CH, Su Y. Thymosin beta-4 knockdown in IEC-6 normal intestinal epithelial cells induces DNA re-replication via downregulating Emi1. J Cell Physiol 2014; 229:1639-46. [PMID: 24615569 DOI: 10.1002/jcp.24609] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Accepted: 03/04/2014] [Indexed: 12/19/2022]
Abstract
Thymosin β4 (Tβ4 ) is a multifunctional protein already used clinically to treat various diseases; however, the promoting effect of this protein on tumor malignancy should not be neglected. Here, we assessed whether Tβ4 alteration influences normal intestinal epithelial cells because Tβ4 is deemed a novel target for treating colorectal cancer (CRC). For this purpose, we examined the consequences of shRNA-mediated knockdown of Tβ4 in IEC-6 normal rat small intestinal cells and found that inhibiting Tβ4 expression significantly suppressed their growth and induced apoptosis in some cells. Flow cytometric analysis further revealed a marked decrease of G0/G1 population but a drastic increase of polyploid ones in these cells. The increase of polyploidy likely resulted from DNA re-replication because not only the de novo DNA synthesis was greatly increased but also the expression levels of Cdc6 (a replication-licensing factor), cyclin A, and phosphorylated-checkpoint kinase 1 were all dramatically elevated. Moreover, marked reductions in both RNA and protein levels of Emi1 (early mitotic inhibitor 1) were also detected in Tβ4 -downregulated IEC-6 cells which might be accounted by the downregulation of E2F1, a transcription factor capable of inducing Emi1 expression, mediated by glycogen synthase-3β (GSK-3β). To our best knowledge, this is the first report showing that inhibiting Tβ4 expression triggers DNA re-replication in normal intestinal epithelial cells, suggesting that this G-actin sequester may play a crucial role in maintaining genome stability in these cells. More importantly, clinical oncologists should take this novel activity into consideration when design CRC therapy based on targeting Tβ4 .
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Affiliation(s)
- Ta-Chung Chao
- Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan; Division of Hematology and Oncology, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
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44
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Truong LN, Li Y, Sun E, Ang K, Hwang PYH, Wu X. Homologous recombination is a primary pathway to repair DNA double-strand breaks generated during DNA rereplication. J Biol Chem 2014; 289:28910-23. [PMID: 25160628 DOI: 10.1074/jbc.m114.576488] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Re-initiation of DNA replication at origins within a given cell cycle would result in DNA rereplication, which can lead to genome instability and tumorigenesis. DNA rereplication can be induced by loss of licensing control at cellular replication origins, or by viral protein-driven multiple rounds of replication initiation at viral origins. DNA double-strand breaks (DSBs) are generated during rereplication, but the mechanisms of how these DSBs are repaired to maintain genome stability and cell viability are poorly understood in mammalian cells. We generated novel EGFP-based DSB repair substrates, which specifically monitor the repair of rereplication-associated DSBs. We demonstrated that homologous recombination (HR) is an important mechanism to repair rereplication-associated DSBs, and sister chromatids are used as templates for such HR-mediated DSB repair. Micro-homology-mediated non-homologous end joining (MMEJ) can also be used but to a lesser extent compared to HR, whereas Ku-dependent classical non-homologous end joining (C-NHEJ) has a minimal role to repair rereplication-associated DSBs. In addition, loss of HR activity leads to severe cell death when rereplication is induced. Therefore, our studies identify HR, the most conservative repair pathway, as the primary mechanism to repair DSBs upon rereplication.
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Affiliation(s)
- Lan N Truong
- From the Department of Molecular and Experimental Medicine, The Scripps Research Institute, La, Jolla, California 92037
| | - Yongjiang Li
- From the Department of Molecular and Experimental Medicine, The Scripps Research Institute, La, Jolla, California 92037
| | - Emily Sun
- From the Department of Molecular and Experimental Medicine, The Scripps Research Institute, La, Jolla, California 92037
| | - Katrina Ang
- From the Department of Molecular and Experimental Medicine, The Scripps Research Institute, La, Jolla, California 92037
| | - Patty Yi-Hwa Hwang
- From the Department of Molecular and Experimental Medicine, The Scripps Research Institute, La, Jolla, California 92037
| | - Xiaohua Wu
- From the Department of Molecular and Experimental Medicine, The Scripps Research Institute, La, Jolla, California 92037
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45
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Riera A, Tognetti S, Speck C. Helicase loading: how to build a MCM2-7 double-hexamer. Semin Cell Dev Biol 2014; 30:104-9. [PMID: 24637008 DOI: 10.1016/j.semcdb.2014.03.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 03/06/2014] [Indexed: 12/27/2022]
Abstract
A central step in eukaryotic initiation of DNA replication is the loading of the helicase at replication origins, misregulation of this reaction leads to DNA damage and genome instability. Here we discuss how the helicase becomes recruited to origins and loaded into a double-hexamer around double-stranded DNA. We specifically describe the individual steps in complex assembly and explain how this process is regulated to maintain genome stability. Structural analysis of the helicase loader and the helicase has provided key insights into the process of double-hexamer formation. A structural comparison of the bacterial and eukaryotic system suggests a mechanism of helicase loading.
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Affiliation(s)
- Alberto Riera
- DNA Replication Group, Faculty of Medicine, Institute of Clinical Sciences, Imperial College, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Silvia Tognetti
- DNA Replication Group, Faculty of Medicine, Institute of Clinical Sciences, Imperial College, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Christian Speck
- DNA Replication Group, Faculty of Medicine, Institute of Clinical Sciences, Imperial College, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK.
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Ayuda-Durán P, Devesa F, Gomes F, Sequeira-Mendes J, Avila-Zarza C, Gómez M, Calzada A. The CDK regulators Cdh1 and Sic1 promote efficient usage of DNA replication origins to prevent chromosomal instability at a chromosome arm. Nucleic Acids Res 2014; 42:7057-68. [PMID: 24753426 PMCID: PMC4066753 DOI: 10.1093/nar/gku313] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Robustness and completion of DNA replication rely on redundant DNA replication origins. Reduced efficiency of origin licensing is proposed to contribute to chromosome instability in CDK-deregulated cell cycles, a frequent alteration in oncogenesis. However, the mechanism by which this instability occurs is largely unknown. Current models suggest that limited origin numbers would reduce fork density favouring chromosome rearrangements, but experimental support in CDK-deregulated cells is lacking. We have investigated the pattern of origin firing efficiency in budding yeast cells lacking the CDK regulators Cdh1 and Sic1. We show that each regulator is required for efficient origin activity, and that both cooperate non-redundantly. Notably, origins are differentially sensitive to CDK deregulation. Origin sensitivity is independent on normal origin efficiency, firing timing or chromosomal location. Interestingly, at a chromosome arm, there is a shortage of origin firing involving active and dormant origins, and the extent of shortage correlates with the severity of CDK deregulation and chromosome instability. We therefore propose that CDK deregulation in G1 phase compromises origin redundancy by decreasing the number of active and dormant origins, leading to origin shortage and increased chromosome instability.
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Affiliation(s)
- Pilar Ayuda-Durán
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología CNB-CSIC, Darwin 3, Madrid 28049, Spain
| | - Fernando Devesa
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología CNB-CSIC, Darwin 3, Madrid 28049, Spain
| | - Fábia Gomes
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología CNB-CSIC, Darwin 3, Madrid 28049, Spain
| | - Joana Sequeira-Mendes
- Centro de Biología Molecular Severo Ochoa CBMSO-CSIC/UAM, Nicolás Cabrera 1, Madrid 28049, Spain
| | | | - María Gómez
- Centro de Biología Molecular Severo Ochoa CBMSO-CSIC/UAM, Nicolás Cabrera 1, Madrid 28049, Spain
| | - Arturo Calzada
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología CNB-CSIC, Darwin 3, Madrid 28049, Spain
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47
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Turner RL, Wilkinson JC, Ornelles DA. E1B and E4 oncoproteins of adenovirus antagonize the effect of apoptosis inducing factor. Virology 2014; 456-457:205-19. [PMID: 24889240 DOI: 10.1016/j.virol.2014.03.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 02/28/2014] [Accepted: 03/10/2014] [Indexed: 01/03/2023]
Abstract
Adenovirus inundates the productively infected cell with linear, double-stranded DNA and an abundance of single-stranded DNA. The cellular response to this stimulus is antagonized by the adenoviral E1B and E4 early genes. A mutant group C adenovirus that fails to express the E1B-55K and E4orf3 genes is unable to suppress the DNA-damage response. Cells infected with this double-mutant virus display significant morphological heterogeneity at late times of infection and frequently contain fragmented nuclei. Nuclear fragmentation was due to the translocation of apoptosis inducing factor (AIF) from the mitochondria into the nucleus. The release of AIF was dependent on active poly(ADP-ribose) polymerase-1 (PARP-1), which appeared to be activated by viral DNA replication. Nuclear fragmentation did not occur in AIF-deficient cells or in cells treated with a PARP-1 inhibitor. The E1B-55K or E4orf3 proteins independently prevented nuclear fragmentation subsequent to PARP-1 activation, possibly by altering the intracellular distribution of PAR-modified proteins.
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Affiliation(s)
- Roberta L Turner
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States
| | - John C Wilkinson
- Department of Biochemistry, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States.
| | - David A Ornelles
- Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States.
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48
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Leman AR, Noguchi E. The replication fork: understanding the eukaryotic replication machinery and the challenges to genome duplication. Genes (Basel) 2014; 4:1-32. [PMID: 23599899 PMCID: PMC3627427 DOI: 10.3390/genes4010001] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Eukaryotic cells must accurately and efficiently duplicate their genomes during each round of the cell cycle. Multiple linear chromosomes, an abundance of regulatory elements, and chromosome packaging are all challenges that the eukaryotic DNA replication machinery must successfully overcome. The replication machinery, the “replisome” complex, is composed of many specialized proteins with functions in supporting replication by DNA polymerases. Efficient replisome progression relies on tight coordination between the various factors of the replisome. Further, replisome progression must occur on less than ideal templates at various genomic loci. Here, we describe the functions of the major replisome components, as well as some of the obstacles to efficient DNA replication that the replisome confronts. Together, this review summarizes current understanding of the vastly complicated task of replicating eukaryotic DNA.
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Affiliation(s)
- Adam R. Leman
- Authors to whom correspondence should be addressed; E-Mails: (A.R.L.); (E.N.); Tel.: +1-215-762-4825 (E.N.); Fax: +1-215-762-4452 (E.N.)
| | - Eishi Noguchi
- Authors to whom correspondence should be addressed; E-Mails: (A.R.L.); (E.N.); Tel.: +1-215-762-4825 (E.N.); Fax: +1-215-762-4452 (E.N.)
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49
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Neelsen KJ, Zanini IM, Mijic S, Herrador R, Zellweger R, Ray Chaudhuri A, Creavin KD, Blow JJ, Lopes M. Deregulated origin licensing leads to chromosomal breaks by rereplication of a gapped DNA template. Genes Dev 2013; 27:2537-42. [PMID: 24298053 PMCID: PMC3861667 DOI: 10.1101/gad.226373.113] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 10/30/2013] [Indexed: 01/01/2023]
Abstract
Deregulated origin licensing and rereplication promote genome instability and tumorigenesis by largely elusive mechanisms. Investigating the consequences of Early mitotic inhibitor 1 (Emi1) depletion in human cells, previously associated with rereplication, we show by DNA fiber labeling that origin reactivation occurs rapidly, well before accumulation of cells with >4N DNA, and is associated with checkpoint-blind ssDNA gaps and replication fork reversal. Massive RPA chromatin loading, formation of small chromosomal fragments, and checkpoint activation occur only later, once cells complete bulk DNA replication. We propose that deregulated origin firing leads to undetected discontinuities on newly replicated DNA, which ultimately cause breakage of rereplicating forks.
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Affiliation(s)
- Kai J. Neelsen
- Institute of Molecular Cancer Research, University of Zurich, CH-8057 Zurich, Switzerland
| | - Isabella M.Y. Zanini
- Institute of Molecular Cancer Research, University of Zurich, CH-8057 Zurich, Switzerland
| | - Sofija Mijic
- Institute of Molecular Cancer Research, University of Zurich, CH-8057 Zurich, Switzerland
| | - Raquel Herrador
- Institute of Molecular Cancer Research, University of Zurich, CH-8057 Zurich, Switzerland
| | - Ralph Zellweger
- Institute of Molecular Cancer Research, University of Zurich, CH-8057 Zurich, Switzerland
| | - Arnab Ray Chaudhuri
- Institute of Molecular Cancer Research, University of Zurich, CH-8057 Zurich, Switzerland
| | - Kevin D. Creavin
- Centre for Gene Regulation and Expression, University of Dundee, Dundee DD1 5EH, United Kingdom
| | - J. Julian Blow
- Centre for Gene Regulation and Expression, University of Dundee, Dundee DD1 5EH, United Kingdom
| | - Massimo Lopes
- Institute of Molecular Cancer Research, University of Zurich, CH-8057 Zurich, Switzerland
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50
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Chodavarapu S, Felczak MM, Simmons LA, Murillo A, Kaguni JM. Mutant DnaAs of Escherichia coli that are refractory to negative control. Nucleic Acids Res 2013; 41:10254-67. [PMID: 23990329 PMCID: PMC3905854 DOI: 10.1093/nar/gkt774] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
DnaA is the initiator of DNA replication in bacteria. A mutant DnaA named DnaAcos is unusual because it is refractory to negative regulation. We developed a genetic method to isolate other mutant DnaAs that circumvent regulation to extend our understanding of mechanisms that control replication initiation. Like DnaAcos, one mutant bearing a tyrosine substitution for histidine 202 (H202Y) withstands the regulation exerted by datA, hda and dnaN (β clamp), and both DnaAcos and H202Y resist inhibition by the Hda-β clamp complex in vitro. Other mutant DnaAs carrying G79D, E244K, V303M or E445K substitutions are either only partially sensitive or refractory to inhibition by the Hda-β clamp complex in vitro but are responsive to hda expression in vivo. All mutant DnaAs remain able to interact directly with Hda. Of interest, both DnaAcos and DnaAE244K bind more avidly to Hda. These mutants, by sequestrating Hda, may limit its availability to regulate other DnaA molecules, which remain active to induce extra rounds of DNA replication. Other evidence suggests that a mutant bearing a V292M substitution hyperinitiates by escaping the effect of an unknown regulatory factor. Together, our results provide new insight into the mechanisms that regulate replication initiation in Escherichia coli.
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Affiliation(s)
- Sundari Chodavarapu
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824-1319, USA and Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA
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