1
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Radhakrishnan A, Gangopadhyay R, Sharma C, Kapardar RK, Sharma NK, Srivastav R. Unwinding Helicase MCM Functionality for Diagnosis and Therapeutics of Replication Abnormalities Associated with Cancer: A Review. Mol Diagn Ther 2024; 28:249-264. [PMID: 38530633 DOI: 10.1007/s40291-024-00701-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/28/2024] [Indexed: 03/28/2024]
Abstract
The minichromosome maintenance (MCM) protein is a component of an active helicase that is essential for the initiation of DNA replication. Dysregulation of MCM functions contribute to abnormal cell proliferation and genomic instability. The interactions of MCM with cellular factors, including Cdc45 and GINS, determine the formation of active helicase and functioning of helicase. The functioning of MCM determines the fate of DNA replication and, thus, genomic integrity. This complex is upregulated in precancerous cells and can act as an important tool for diagnostic applications. The MCM protein complex can be an important broad-spectrum therapeutic target in various cancers. Investigations have supported the potential and applications of MCM in cancer diagnosis and its therapeutics. In this article, we discuss the physiological roles of MCM and its associated factors in DNA replication and cancer pathogenesis.
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Affiliation(s)
| | - Ritwik Gangopadhyay
- Amity Institute of Biotechnology, Amity University, Noida, Uttar Pradesh, India
| | | | | | - Nilesh Kumar Sharma
- Cancer and Translational Research Lab, Dr. DY Patil Biotechnology and Bioinformatics Institute, Dr. DY Patil Vidyapeeth, Pune, Maharashtra, India
| | - Rajpal Srivastav
- Amity Institute of Biotechnology, Amity University, Noida, Uttar Pradesh, India.
- Department of Science and Technology, Ministry of Science and Technology, New Delhi, India.
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2
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Solving the MCM paradox by visualizing the scaffold of CMG helicase at active replisomes. Nat Commun 2022; 13:6090. [PMID: 36241664 PMCID: PMC9568601 DOI: 10.1038/s41467-022-33887-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Accepted: 10/05/2022] [Indexed: 12/24/2022] Open
Abstract
Genome duplication is safeguarded by constantly adjusting the activity of the replicative CMG (CDC45-MCM2-7-GINS) helicase. However, minichromosome maintenance proteins (MCMs)-the structural core of the CMG helicase-have never been visualized at sites of DNA synthesis inside a cell (the so-called MCM paradox). Here, we solve this conundrum by showing that anti-MCM antibodies primarily detect inactive MCMs. Upon conversion of inactive MCMs to CMGs, factors that are required for replisome activity bind to the MCM scaffold and block MCM antibody binding sites. Tagging of endogenous MCMs by CRISPR-Cas9 bypasses this steric hindrance and enables MCM visualization at active replisomes. Thus, by defining conditions for detecting the structural core of the replicative CMG helicase, our results explain the MCM paradox, provide visual proof that MCMs are an integral part of active replisomes in vivo, and enable the investigation of replication dynamics in living cells exposed to a constantly changing environment.
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3
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Safeguarding DNA Replication: A Golden Touch of MiDAS and Other Mechanisms. Int J Mol Sci 2022; 23:ijms231911331. [PMID: 36232633 PMCID: PMC9570362 DOI: 10.3390/ijms231911331] [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: 08/12/2022] [Revised: 09/19/2022] [Accepted: 09/20/2022] [Indexed: 11/21/2022] Open
Abstract
DNA replication is a tightly regulated fundamental process allowing the correct duplication and transfer of the genetic information from the parental cell to the progeny. It involves the coordinated assembly of several proteins and protein complexes resulting in replication fork licensing, firing and progression. However, the DNA replication pathway is strewn with hurdles that affect replication fork progression during S phase. As a result, cells have adapted several mechanisms ensuring replication completion before entry into mitosis and segregating chromosomes with minimal, if any, abnormalities. In this review, we describe the possible obstacles that a replication fork might encounter and how the cell manages to protect DNA replication from S to the next G1.
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4
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Mei L, Kedziora KM, Song EA, Purvis JE, Cook J. The consequences of differential origin licensing dynamics in distinct chromatin environments. Nucleic Acids Res 2022; 50:9601-9620. [PMID: 35079814 PMCID: PMC9508807 DOI: 10.1093/nar/gkac003] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 12/17/2021] [Accepted: 01/05/2022] [Indexed: 02/01/2023] Open
Abstract
Eukaryotic chromosomes contain regions of varying accessibility, yet DNA replication factors must access all regions. The first replication step is loading MCM complexes to license replication origins during the G1 cell cycle phase. It is not yet known how mammalian MCM complexes are adequately distributed to both accessible euchromatin regions and less accessible heterochromatin regions. To address this question, we combined time-lapse live-cell imaging with immunofluorescence imaging of single human cells to quantify the relative rates of MCM loading in euchromatin and heterochromatin throughout G1. We report here that MCM loading in euchromatin is faster than that in heterochromatin in early G1, but surprisingly, heterochromatin loading accelerates relative to euchromatin loading in middle and late G1. This differential acceleration allows both chromatin types to begin S phase with similar concentrations of loaded MCM. The different loading dynamics require ORCA-dependent differences in origin recognition complex distribution. A consequence of heterochromatin licensing dynamics is that cells experiencing a truncated G1 phase from premature cyclin E expression enter S phase with underlicensed heterochromatin, and DNA damage accumulates preferentially in heterochromatin in the subsequent S/G2 phase. Thus, G1 length is critical for sufficient MCM loading, particularly in heterochromatin, to ensure complete genome duplication and to maintain genome stability.
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Affiliation(s)
- Liu Mei
- Department of Biochemistry & Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Katarzyna M Kedziora
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Bioinformatics and Analytics Research Collaborative (BARC), University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Eun-Ah Song
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jeremy E Purvis
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jeanette Gowen Cook
- Department of Biochemistry & Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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5
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Efficiency and equity in origin licensing to ensure complete DNA replication. Biochem Soc Trans 2021; 49:2133-2141. [PMID: 34545932 DOI: 10.1042/bst20210161] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 08/19/2021] [Accepted: 08/31/2021] [Indexed: 12/21/2022]
Abstract
The cell division cycle must be strictly regulated during both development and adult maintenance, and efficient and well-controlled DNA replication is a key event in the cell cycle. DNA replication origins are prepared in G1 phase of the cell cycle in a process known as origin licensing which is essential for DNA replication initiation in the subsequent S phase. Appropriate origin licensing includes: (1) Licensing enough origins at adequate origin licensing speed to complete licensing before G1 phase ends; (2) Licensing origins such that they are well-distributed on all chromosomes. Both aspects of licensing are critical for replication efficiency and accuracy. In this minireview, we will discuss recent advances in defining how origin licensing speed and distribution are critical to ensure DNA replication completion and genome stability.
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6
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Abstract
Safeguards against excess DNA replication are often dysregulated in cancer, and driving cancer cells towards over-replication is a promising therapeutic strategy. We determined DNA synthesis patterns in cancer cells undergoing partial genome re-replication due to perturbed regulatory interactions (re-replicating cells). These cells exhibited slow replication, increased frequency of replication initiation events, and a skewed initiation pattern that preferentially reactivated early-replicating origins. Unlike in cells exposed to replication stress, which activated a novel group of hitherto unutilized (dormant) replication origins, the preferred re-replicating origins arose from the same pool of potential origins as those activated during normal growth. Mechanistically, the skewed initiation pattern reflected a disproportionate distribution of pre-replication complexes on distinct regions of licensed chromatin prior to replication. This distinct pattern suggests that circumventing the strong inhibitory interactions that normally prevent excess DNA synthesis can occur via at least two pathways, each activating a distinct set of replication origins.
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7
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Abstract
The recruitment of the minichromosome maintenance complex (MCM) on DNA replication origins is a critical process for faithful genome duplication termed licensing. Aberrant licensing has been associated with cancer and, recently, with neurodevelopmental diseases. Investigating MCM loading in complicated tissues, such as brain, remains challenging. Here, we describe an optimized approach for the qualitative and quantitative analysis of DNA-bound MCMs in the developing mouse cortex through direct imaging, offering an innovative insight into the research of origin licensing in vivo.
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8
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Panagopoulos A, Taraviras S, Nishitani H, Lygerou Z. CRL4Cdt2: Coupling Genome Stability to Ubiquitination. Trends Cell Biol 2020; 30:290-302. [DOI: 10.1016/j.tcb.2020.01.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 01/12/2020] [Accepted: 01/14/2020] [Indexed: 12/20/2022]
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9
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Champeris Tsaniras S, Delinasios GJ, Petropoulos M, Panagopoulos A, Anagnostopoulos AK, Villiou M, Vlachakis D, Bravou V, Stathopoulos GT, Taraviras S. DNA Replication Inhibitor Geminin and Retinoic Acid Signaling Participate in Complex Interactions Associated With Pluripotency. Cancer Genomics Proteomics 2019; 16:593-601. [PMID: 31659113 PMCID: PMC6885373 DOI: 10.21873/cgp.20162] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 09/23/2019] [Accepted: 10/10/2019] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND/AIM Several links between DNA replication, pluripotency and development have been recently identified. The involvement of miRNA in the regulation of cell cycle events and pluripotency factors has also gained attention. MATERIALS AND METHODS In the present study, we used the g:Profiler platform to analyze transcription factor binding sites, miRNA networks and protein-protein interactions to identify novel links among the aforementioned processes. RESULTS AND CONCLUSION A complex circuitry between retinoic acid signaling, SWI/SNF components, pluripotency factors including Oct4, Sox2 and Nanog and cell cycle regulators was identified. It is suggested that the DNA replication inhibitor geminin plays a central role in this circuitry.
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Affiliation(s)
- Spyridon Champeris Tsaniras
- Department of Physiology, Medical School, University of Patras, Patras, Greece
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, U.S.A
| | | | | | | | - Athanasios K Anagnostopoulos
- International Institute of Anticancer Research, Kapandriti, Greece
- Proteomics Research Unit, Biomedical Research Foundation of the Academy of Athens, Athens, Greece
| | - Maria Villiou
- Department of Physiology, Medical School, University of Patras, Patras, Greece
| | - Dimitrios Vlachakis
- Bioinformatics & Medical Informatics Laboratory, Biomedical Research Foundation of the Academy of Athens, Athens, Greece
| | - Vasiliki Bravou
- Department of Anatomy-Histology-Embryology, Faculty of Medicine, University of Patras, Patras, Greece
| | - Georgios T Stathopoulos
- Laboratory for Molecular Respiratory Carcinogenesis, Department of Physiology, Faculty of Medicine, University of Patras, Patras, Greece
| | - Stavros Taraviras
- Department of Physiology, Medical School, University of Patras, Patras, Greece
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10
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Dutta P, Islam S, Choppara S, Sengupta P, Kumar A, Kumar A, Wani MR, Chatterjee S, Santra MK. The tumor suppressor FBXO31 preserves genomic integrity by regulating DNA replication and segregation through precise control of cyclin A levels. J Biol Chem 2019; 294:14879-14895. [PMID: 31413110 DOI: 10.1074/jbc.ra118.007055] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 08/09/2019] [Indexed: 11/06/2022] Open
Abstract
F-box protein 31 (FBXO31) is a reported putative tumor suppressor, and its inactivation due to loss of heterozygosity is associated with cancers of different origins. An emerging body of literature has documented FBXO31's role in preserving genome integrity following DNA damage and in the cell cycle. However, knowledge regarding the role of FBXO31 during normal cell-cycle progression is restricted to its functions during the G2/M phase. Interestingly, FBXO31 levels remain high even during the early G1 phase, a crucial stage for preparing the cells for DNA replication. Therefore, we sought to investigate the functions of FBXO31 during the G1 phase of the cell cycle. Here, using flow cytometric, biochemical, and immunofluorescence techniques, we show that FBXO31 is essential for maintaining optimum expression of the cell-cycle protein cyclin A for efficient cell-cycle progression. Stable FBXO31 knockdown led to atypical accumulation of cyclin A during the G1 phase, driving premature DNA replication and compromised loading of the minichromosome maintenance complex, resulting in replication from fewer origins and DNA double-strand breaks. Because of these inherent defects in replication, FBXO31-knockdown cells were hypersensitive to replication stress-inducing agents and displayed pronounced genomic instability. Upon entering mitosis, the cells defective in DNA replication exhibited a delay in the prometaphase-to-metaphase transition and anaphase defects such as lagging and bridging chromosomes. In conclusion, our findings establish that FBXO31 plays a pivotal role in preserving genomic integrity by maintaining low cyclin A levels during the G1 phase for faithful genome duplication and segregation.
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Affiliation(s)
- Parul Dutta
- National Centre for Cell Science, NCCS Complex, Ganeshkhind Road, Pune, Maharashtra 411007, India.,Department of Biotechnology, Savitribai Phule Pune University, Ganeshkhind Road, Pune, Maharashtra 411007, India
| | - Sehbanul Islam
- National Centre for Cell Science, NCCS Complex, Ganeshkhind Road, Pune, Maharashtra 411007, India.,Department of Biotechnology, Savitribai Phule Pune University, Ganeshkhind Road, Pune, Maharashtra 411007, India
| | - Srinadh Choppara
- National Centre for Cell Science, NCCS Complex, Ganeshkhind Road, Pune, Maharashtra 411007, India.,Department of Biotechnology, Savitribai Phule Pune University, Ganeshkhind Road, Pune, Maharashtra 411007, India
| | | | - Anil Kumar
- National Centre for Cell Science, NCCS Complex, Ganeshkhind Road, Pune, Maharashtra 411007, India.,Department of Biotechnology, Savitribai Phule Pune University, Ganeshkhind Road, Pune, Maharashtra 411007, India
| | - Avinash Kumar
- National Centre for Cell Science, NCCS Complex, Ganeshkhind Road, Pune, Maharashtra 411007, India.,Arnold and Marie Schwartz College of Pharmacy and Health Sciences, Long Island University, Brooklyn, New York 11201
| | - Mohan R Wani
- National Centre for Cell Science, NCCS Complex, Ganeshkhind Road, Pune, Maharashtra 411007, India
| | | | - Manas Kumar Santra
- National Centre for Cell Science, NCCS Complex, Ganeshkhind Road, Pune, Maharashtra 411007, India
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11
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Koulouras G, Panagopoulos A, Rapsomaniki MA, Giakoumakis NN, Taraviras S, Lygerou Z. EasyFRAP-web: a web-based tool for the analysis of fluorescence recovery after photobleaching data. Nucleic Acids Res 2019; 46:W467-W472. [PMID: 29901776 PMCID: PMC6030846 DOI: 10.1093/nar/gky508] [Citation(s) in RCA: 76] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 05/23/2018] [Indexed: 01/12/2023] Open
Abstract
Understanding protein dynamics is crucial in order to elucidate protein function and interactions. Advances in modern microscopy facilitate the exploration of the mobility of fluorescently tagged proteins within living cells. Fluorescence recovery after photobleaching (FRAP) is an increasingly popular functional live-cell imaging technique which enables the study of the dynamic properties of proteins at a single-cell level. As an increasing number of labs generate FRAP datasets, there is a need for fast, interactive and user-friendly applications that analyze the resulting data. Here we present easyFRAP-web, a web application that simplifies the qualitative and quantitative analysis of FRAP datasets. EasyFRAP-web permits quick analysis of FRAP datasets through an intuitive web interface with interconnected analysis steps (experimental data assessment, different types of normalization and estimation of curve-derived quantitative parameters). In addition, easyFRAP-web provides dynamic and interactive data visualization and data and figure export for further analysis after every step. We test easyFRAP-web by analyzing FRAP datasets capturing the mobility of the cell cycle regulator Cdt2 in the presence and absence of DNA damage in cultured cells. We show that easyFRAP-web yields results consistent with previous studies and highlights cell-to-cell heterogeneity in the estimated kinetic parameters. EasyFRAP-web is platform-independent and is freely accessible at: https://easyfrap.vmnet.upatras.gr/.
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Affiliation(s)
- Grigorios Koulouras
- Department of Biology, School of Medicine, University of Patras, Rio, Patras 26505, Greece
| | - Andreas Panagopoulos
- Department of Biology, School of Medicine, University of Patras, Rio, Patras 26505, Greece
| | - Maria A Rapsomaniki
- Department of Biology, School of Medicine, University of Patras, Rio, Patras 26505, Greece
| | | | - Stavros Taraviras
- Department of Physiology, School of Medicine, University of Patras, Rio, Patras 26505, Greece
| | - Zoi Lygerou
- Department of Biology, School of Medicine, University of Patras, Rio, Patras 26505, Greece
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12
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Lalioti ME, Arbi M, Loukas I, Kaplani K, Kalogeropoulou A, Lokka G, Kyrousi C, Mizi A, Georgomanolis T, Josipovic N, Gkikas D, Benes V, Politis PK, Papantonis A, Lygerou Z, Taraviras S. GemC1 governs multiciliogenesis through direct interaction with and transcriptional regulation of p73. J Cell Sci 2019; 132:jcs.228684. [PMID: 31028178 DOI: 10.1242/jcs.228684] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 04/16/2019] [Indexed: 12/11/2022] Open
Abstract
A distinct combination of transcription factors elicits the acquisition of a specific fate and the initiation of a differentiation program. Multiciliated cells (MCCs) are a specialized type of epithelial cells that possess dozens of motile cilia on their apical surface. Defects in cilia function have been associated with ciliopathies that affect many organs, including brain and airway epithelium. Here we show that the geminin coiled-coil domain-containing protein 1 GemC1 (also known as Lynkeas) regulates the transcriptional activation of p73, a transcription factor central to multiciliogenesis. Moreover, we show that GemC1 acts in a trimeric complex with transcription factor E2F5 and tumor protein p73 (officially known as TP73), and that this complex is important for the activation of the p73 promoter. We also provide in vivo evidence that GemC1 is necessary for p73 expression in different multiciliated epithelia. We further show that GemC1 regulates multiciliogenesis through the control of chromatin organization, and the epigenetic marks/tags of p73 and Foxj 1. Our results highlight novel signaling cues involved in the commitment program of MCCs across species and tissues.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Maria-Eleni Lalioti
- Department of Physiology, School of Medicine, University of Patras, 26504 Patras, Greece
| | - Marina Arbi
- Department of General Biology, School of Medicine, University of Patras, Patras 26504, Greece
| | - Ioannis Loukas
- Department of General Biology, School of Medicine, University of Patras, Patras 26504, Greece
| | - Konstantina Kaplani
- Department of Physiology, School of Medicine, University of Patras, 26504 Patras, Greece
| | - Argyro Kalogeropoulou
- Department of Physiology, School of Medicine, University of Patras, 26504 Patras, Greece
| | - Georgia Lokka
- Department of Physiology, School of Medicine, University of Patras, 26504 Patras, Greece
| | - Christina Kyrousi
- Department of Physiology, School of Medicine, University of Patras, 26504 Patras, Greece
| | - Athanasia Mizi
- Center for Molecular Medicine Cologne, University of Cologne, Robert-Koch-Str. 21, 50931 Cologne, Germany.,Department of Pathology, University Medical Center Göttingen, Robert-Koch-Str. 40, 37075 Göttingen, Germany
| | - Theodore Georgomanolis
- Center for Molecular Medicine Cologne, University of Cologne, Robert-Koch-Str. 21, 50931 Cologne, Germany
| | - Natasa Josipovic
- Center for Molecular Medicine Cologne, University of Cologne, Robert-Koch-Str. 21, 50931 Cologne, Germany.,Department of Pathology, University Medical Center Göttingen, Robert-Koch-Str. 40, 37075 Göttingen, Germany
| | - Dimitrios Gkikas
- Department of Center for Basic Research, Biomedical Research Foundation of the Academy of Athens, 4 Soranou Efesiou Street, 115 27 Athens, Greece
| | - Vladimir Benes
- European Molecular Biology Laboratory (EMBL), Core Facilities and Services, Meyerhofstraße 1, Heidelberg 69117, Germany
| | - Panagiotis K Politis
- Department of Center for Basic Research, Biomedical Research Foundation of the Academy of Athens, 4 Soranou Efesiou Street, 115 27 Athens, Greece
| | - Argyris Papantonis
- Center for Molecular Medicine Cologne, University of Cologne, Robert-Koch-Str. 21, 50931 Cologne, Germany.,Department of Pathology, University Medical Center Göttingen, Robert-Koch-Str. 40, 37075 Göttingen, Germany
| | - Zoi Lygerou
- Department of General Biology, School of Medicine, University of Patras, Patras 26504, Greece
| | - Stavros Taraviras
- Department of Physiology, School of Medicine, University of Patras, 26504 Patras, Greece
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13
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Petropoulos M, Champeris Tsaniras S, Taraviras S, Lygerou Z. Replication Licensing Aberrations, Replication Stress, and Genomic Instability. Trends Biochem Sci 2019; 44:752-764. [PMID: 31054805 DOI: 10.1016/j.tibs.2019.03.011] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 03/24/2019] [Accepted: 03/27/2019] [Indexed: 01/07/2023]
Abstract
Strict regulation of DNA replication is of fundamental significance for the maintenance of genome stability. Licensing of origins of DNA replication is a critical event for timely genome duplication. Errors in replication licensing control lead to genomic instability across evolution. Here, we present accumulating evidence that aberrant replication licensing is linked to oncogene-induced replication stress and poses a major threat to genome stability, promoting tumorigenesis. Oncogene activation can lead to defects in where along the genome and when during the cell cycle licensing takes place, resulting in replication stress. We also discuss the potential of replication licensing as a specific target for novel anticancer therapies.
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Affiliation(s)
- Michalis Petropoulos
- Department of Biology, School of Medicine, University of Patras, Patras 26504, Greece
| | | | - Stavros Taraviras
- Department of Physiology, School of Medicine, University of Patras, Patras 26504, Greece.
| | - Zoi Lygerou
- Department of Biology, School of Medicine, University of Patras, Patras 26504, Greece.
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14
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Moiseeva TN, Bakkenist CJ. Regulation of the initiation of DNA replication in human cells. DNA Repair (Amst) 2018; 72:99-106. [PMID: 30266203 DOI: 10.1016/j.dnarep.2018.09.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 09/07/2018] [Indexed: 12/31/2022]
Abstract
The origin of species would not have been possible without high fidelity DNA replication and complex genomes evolved with mechanisms that control the initiation of DNA replication at multiple origins on multiple chromosomes such that the genome is duplicated once and only once. The mechanisms that control the assembly and activation of the replicative helicase and the initiation of DNA replication in yeast and Xenopus egg extract systems have been identified and reviewed [1,2]. The goal of this review is to organize currently available data on the mechanisms that control the initiation of DNA replication in human cells.
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Affiliation(s)
- Tatiana N Moiseeva
- Department of Radiation Oncology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
| | - Christopher J Bakkenist
- Department of Radiation Oncology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA; Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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15
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Carroll TD, Newton IP, Chen Y, Blow JJ, Näthke I. Lgr5 + intestinal stem cells reside in an unlicensed G 1 phase. J Cell Biol 2018; 217:1667-1685. [PMID: 29599208 PMCID: PMC5940300 DOI: 10.1083/jcb.201708023] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 01/23/2018] [Accepted: 02/27/2018] [Indexed: 12/21/2022] Open
Abstract
During late mitosis and the early G1 phase, the origins of replication are licensed by binding to double hexamers of MCM2-7. In this study, we investigated how licensing and proliferative commitment are coupled in the epithelium of the small intestine. We developed a method for identifying cells in intact tissue containing DNA-bound MCM2-7. Interphase cells above the transit-amplifying compartment had no DNA-bound MCM2-7, but still expressed the MCM2-7 protein, suggesting that licensing is inhibited immediately upon differentiation. Strikingly, we found most proliferative Lgr5+ stem cells are in an unlicensed state. This suggests that the elongated cell-cycle of intestinal stem cells is caused by an increased G1 length, characterized by dormant periods with unlicensed origins. Significantly, the unlicensed state is lost in Apc-mutant epithelium, which lacks a functional restriction point, causing licensing immediately upon G1 entry. We propose that the unlicensed G1 phase of intestinal stem cells creates a temporal window when proliferative fate decisions can be made.
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Affiliation(s)
- Thomas D Carroll
- Cell and Developmental Biology, University of Dundee, Dundee, Scotland, UK
| | - Ian P Newton
- Cell and Developmental Biology, University of Dundee, Dundee, Scotland, UK
| | - Yu Chen
- Cell and Developmental Biology, University of Dundee, Dundee, Scotland, UK
| | - J Julian Blow
- Centre for Gene Regulation and Expression, University of Dundee, Dundee, Scotland, UK
| | - Inke Näthke
- Cell and Developmental Biology, University of Dundee, Dundee, Scotland, UK
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16
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Matson JP, Dumitru R, Coryell P, Baxley RM, Chen W, Twaroski K, Webber BR, Tolar J, Bielinsky AK, Purvis JE, Cook JG. Rapid DNA replication origin licensing protects stem cell pluripotency. eLife 2017; 6:30473. [PMID: 29148972 PMCID: PMC5720591 DOI: 10.7554/elife.30473] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 11/16/2017] [Indexed: 11/24/2022] Open
Abstract
Complete and robust human genome duplication requires loading minichromosome maintenance (MCM) helicase complexes at many DNA replication origins, an essential process termed origin licensing. Licensing is restricted to G1 phase of the cell cycle, but G1 length varies widely among cell types. Using quantitative single-cell analyses, we found that pluripotent stem cells with naturally short G1 phases load MCM much faster than their isogenic differentiated counterparts with long G1 phases. During the earliest stages of differentiation toward all lineages, MCM loading slows concurrently with G1 lengthening, revealing developmental control of MCM loading. In contrast, ectopic Cyclin E overproduction uncouples short G1 from fast MCM loading. Rapid licensing in stem cells is caused by accumulation of the MCM loading protein, Cdt1. Prematurely slowing MCM loading in pluripotent cells not only lengthens G1 but also accelerates differentiation. Thus, rapid origin licensing is an intrinsic characteristic of stem cells that contributes to pluripotency maintenance. From red blood cells to nerve cells, animals’ bodies contain many different types of specialized cells. These all begin as stem cells, which have the potential to divide and make more stem cells or to specialize. All dividing cells must first unwind their DNA so that it can be copied. To achieve this, cells load DNA-unwinding enzymes called helicases onto their DNA during the part of the cell cycle known as G1 phase. Cells must load enough helicase enzymes to ensure that their DNA is copied completely and in time. Stem cells divide faster than their specialized descendants, and have a much shorter G1 phase too. Yet these cells still manage to load enough helicases to copy their DNA. Little is known about how the amount, rate and timing of helicase loading varies between cells that divide at different speeds. Now Matson et al. have measured how quickly helicase enzymes are loaded onto DNA in individual human cells, including stem cells and specialized or “differentiated” cells. Stem cells loaded helicases rapidly to make up for the short time they spent in G1 phase, while differentiated cells loaded the enzymes more slowly. Measuring how the loading rate changed when stem cells were triggered to specialize showed that helicase loading slowed as the G1 phase got longer. Matson et al. found that the levels of key proteins required for helicase loading correlated with the rates of loading. Altering the levels of the proteins changed how quickly the enzymes were loaded and how the cells behaved – for example, slowing down the loading of helicases made the stem cells specialize quicker. These findings show that the processes of cell differentiation and DNA replication are closely linked. This study and future ones will help scientists understand what is happening during early animal development, when specialization first takes place, as well as what has gone wrong in cancer cells, which also divide quickly. A better understanding of this process also helps in regenerative medicine – where one of the challenges is to make enough specialized cells to transplant into a patient with tissue damage without those cells becoming cancerous.
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Affiliation(s)
- Jacob Peter Matson
- Department of Biochemistry and Biophysics, The University of North Carolina, Chapel Hill, United States
| | - Raluca Dumitru
- Human Pluripotent Stem Cell Core Facility, The University of North Carolina, Chapel Hill, United States
| | - Philip Coryell
- Department of Genetics, The University of North Carolina, Chapel Hill, United States
| | - Ryan M Baxley
- Department of Biochemistry, Molecular Biology, and Biophysics, The University of Minnesota, Minneapolis, United States
| | - Weili Chen
- Stem Cell Institute, University of Minnesota, Minnesota, United States
| | - Kirk Twaroski
- Stem Cell Institute, University of Minnesota, Minnesota, United States
| | - Beau R Webber
- Stem Cell Institute, University of Minnesota, Minnesota, United States
| | - Jakub Tolar
- Stem Cell Institute, University of Minnesota, Minnesota, United States
| | - Anja-Katrin Bielinsky
- Department of Biochemistry, Molecular Biology, and Biophysics, The University of Minnesota, Minneapolis, United States
| | - Jeremy E Purvis
- Department of Genetics, The University of North Carolina, Chapel Hill, United States.,Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, United States
| | - Jeanette Gowen Cook
- Department of Biochemistry and Biophysics, The University of North Carolina, Chapel Hill, United States.,Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, United States
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17
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Shima N, Pederson KD. Dormant origins as a built-in safeguard in eukaryotic DNA replication against genome instability and disease development. DNA Repair (Amst) 2017; 56:166-173. [PMID: 28641940 PMCID: PMC5547906 DOI: 10.1016/j.dnarep.2017.06.019] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
DNA replication is a prerequisite for cell proliferation, yet it can be increasingly challenging for a eukaryotic cell to faithfully duplicate its genome as its size and complexity expands. Dormant origins now emerge as a key component for cells to successfully accomplish such a demanding but essential task. In this perspective, we will first provide an overview of the fundamental processes eukaryotic cells have developed to regulate origin licensing and firing. With a special focus on mammalian systems, we will then highlight the role of dormant origins in preventing replication-associated genome instability and their functional interplay with proteins involved in the DNA damage repair response for tumor suppression. Lastly, deficiencies in the origin licensing machinery will be discussed in relation to their influence on stem cell maintenance and human diseases.
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Affiliation(s)
- Naoko Shima
- The University of Minnesota, Twin Cities, Department of Genetics, Cell Biology and Development, Masonic Cancer Center, 6-160 Jackson Hall, 321 Church St SE., Minneapolis, MN 55455, United States.
| | - Kayla D Pederson
- The University of Minnesota, Twin Cities, Department of Genetics, Cell Biology and Development, Masonic Cancer Center, 6-160 Jackson Hall, 321 Church St SE., Minneapolis, MN 55455, United States
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18
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Giakoumakis NN, Rapsomaniki MA, Lygerou Z. Analysis of Protein Kinetics Using Fluorescence Recovery After Photobleaching (FRAP). Methods Mol Biol 2017; 1563:243-267. [PMID: 28324613 DOI: 10.1007/978-1-4939-6810-7_16] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Fluorescence recovery after photobleaching (FRAP) is a cutting-edge live-cell functional imaging technique that enables the exploration of protein dynamics in individual cells and thus permits the elucidation of protein mobility, function, and interactions at a single-cell level. During a typical FRAP experiment, fluorescent molecules in a defined region of interest within the cell are bleached by a short and powerful laser pulse, while the recovery of the fluorescence in the region is monitored over time by time-lapse microscopy. FRAP experimental setup and image acquisition involve a number of steps that need to be carefully executed to avoid technical artifacts. Equally important is the subsequent computational analysis of FRAP raw data, to derive quantitative information on protein diffusion and binding parameters. Here we present an integrated in vivo and in silico protocol for the analysis of protein kinetics using FRAP. We focus on the most commonly encountered challenges and technical or computational pitfalls and their troubleshooting so that valid and robust insight into protein dynamics within living cells is gained.
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Affiliation(s)
| | - Maria Anna Rapsomaniki
- Laboratory of Biology, School of Medicine, University of Patras, GR26500 Rio, Patras, Greece.,IBM Research Zurich, Säumerstrasse 4, CH-8803, Rüschlikon, Switzerland
| | - Zoi Lygerou
- Laboratory of Biology, School of Medicine, University of Patras, GR26500 Rio, Patras, Greece.
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19
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Pozo PN, Cook JG. Regulation and Function of Cdt1; A Key Factor in Cell Proliferation and Genome Stability. Genes (Basel) 2016; 8:genes8010002. [PMID: 28025526 PMCID: PMC5294997 DOI: 10.3390/genes8010002] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Revised: 12/13/2016] [Accepted: 12/14/2016] [Indexed: 12/30/2022] Open
Abstract
Successful cell proliferation requires efficient and precise genome duplication followed by accurate chromosome segregation. The Cdc10-dependent transcript 1 protein (Cdt1) is required for the first step in DNA replication, and in human cells Cdt1 is also required during mitosis. Tight cell cycle controls over Cdt1 abundance and activity are critical to normal development and genome stability. We review here recent advances in elucidating Cdt1 molecular functions in both origin licensing and kinetochore–microtubule attachment, and we describe the current understanding of human Cdt1 regulation.
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Affiliation(s)
- Pedro N Pozo
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| | - Jeanette Gowen Cook
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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20
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Association of TGFβ signaling with the maintenance of a quiescent stem cell niche in human oral mucosa. Histochem Cell Biol 2016; 146:539-555. [PMID: 27480259 DOI: 10.1007/s00418-016-1473-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/26/2016] [Indexed: 12/26/2022]
Abstract
A dogma in squamous epithelial biology is that proliferation occurs in the basal cell layer. Notable exceptions are squamous epithelia of the human oral cavity, esophagus, ectocervix, and vagina. In these human epithelia, proliferation is rare in the basal cell layer, and the vast majority of cells positive for Ki67 and other proliferation markers are found in para- and suprabasal cell layers. This unique human feature of a generally quiescent basal cell layer overlaid by highly proliferative cells offers the rare opportunity to study the molecular features of undifferentiated, quiescent, putative stem cells in their natural context. Here, we show that the quiescent human oral mucosa basal cell layer expresses putative markers of stemness, while para- and suprabasal cells are characterized by cell cycle genes. We identified a TGFβ signature in this quiescent basal cell layer. In in vitro organotypic cultures, human keratinocytes could be induced to express markers of these quiescent basal cells when TGFβ signaling is activated. The study suggests that the separation of basal cell layer and proliferation in human oral mucosa may function to accommodate high proliferation rates and the protection of a quiescent reserve stem cell pool. Psoriasis, an epidermal inflammatory hyperproliferative disease, exhibits features of a quiescent basal cell layer mimicking normal oral mucosa. Our data indicate that structural changes in the organization of epithelial proliferation could contribute to longevity and carcinogenesis.
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21
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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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22
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Caillat C, Fish A, Pefani DE, Taraviras S, Lygerou Z, Perrakis A. The structure of the GemC1 coiled coil and its interaction with the Geminin family of coiled-coil proteins. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2015; 71:2278-86. [PMID: 26527144 PMCID: PMC4631479 DOI: 10.1107/s1399004715016892] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 09/09/2015] [Indexed: 12/14/2022]
Abstract
GemC1, together with Idas and Geminin, an important regulator of DNA-replication licensing and differentiation decisions, constitute a superfamily sharing a homologous central coiled-coil domain. To better understand this family of proteins, the crystal structure of a GemC1 coiled-coil domain variant engineered for better solubility was determined to 2.2 Å resolution. GemC1 shows a less typical coiled coil compared with the Geminin homodimer and the Geminin-Idas heterodimer structures. It is also shown that both in vitro and in cells GemC1 interacts with Geminin through its coiled-coil domain, forming a heterodimer that is more stable that the GemC1 homodimer. Comparative analysis of the thermal stability of all of the possible superfamily complexes, using circular dichroism to follow the unfolding of the entire helix of the coiled coil, or intrinsic tryptophan fluorescence of a unique conserved N-terminal tryptophan, shows that the unfolding of the coiled coil is likely to take place from the C-terminus towards the N-terminus. It is also shown that homodimers show a single-state unfolding, while heterodimers show a two-state unfolding, suggesting that the dimer first falls apart and the helices then unfold according to the stability of each protein. The findings argue that Geminin-family members form homodimers and heterodimers between them, and this ability is likely to be important for modulating their function in cycling and differentiating cells.
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Affiliation(s)
- Christophe Caillat
- Department of Biochemistry, The Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands
| | - Alexander Fish
- Department of Biochemistry, The Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands
| | | | - Stavros Taraviras
- Laboratory of Physiology, School of Medicine, University of Patras, 26505 Rio, Patras, Greece
| | - Zoi Lygerou
- Laboratory of Biology, School of Medicine, University of Patras, 26505 Rio, Patras, Greece
| | - Anastassis Perrakis
- Department of Biochemistry, The Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands
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23
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Shinya M, Machiki D, Henrich T, Kubota Y, Takisawa H, Mimura S. Evolutionary diversification of MCM3 genes in Xenopus laevis and Danio rerio. Cell Cycle 2015; 13:3271-81. [PMID: 25485507 DOI: 10.4161/15384101.2014.954445] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Embryonic cell cycles of amphibians are rapid and lack zygotic transcription and checkpoint control. At the mid-blastula transition, zygotic transcription is initiated and cell divisions become asynchronous. Several cell cycle-related amphibian genes retain 2 distinct forms, maternal and zygotic, but little is known about the functional differences between these 2 forms of proteins. The minichromosome maintenance (MCM) 2-7 complex, consisting of 6 MCM proteins, plays a central role in the regulation of eukaryotic DNA replication. Almost all eukaryotes retain just a single MCM gene for each subunit. Here we report that Xenopus and zebrafish have 2 copies of MCM3 genes, one of which shows a maternal and the other a zygotic expression pattern. Phylogenetic analysis shows that the Xenopus and zebrafish zygotic MCM3 genes are more similar to their mammalian MCM3 ortholog, suggesting that maternal MCM3 was lost during evolution in most vertebrate lineages. Maternal MCM3 proteins in these 2 species are functionally different from zygotic MCM3 proteins because zygotic, but not maternal, MCM3 possesses an active nuclear localization signal in its C-terminal region, such as mammalian MCM3 orthologs do. mRNA injection experiments in zebrafish embryos show that overexpression of maternal MCM3 impairs proliferation and causes developmental defects, whereas zygotic MCM3 has a much weaker effect. This difference is brought about by the difference in their C-terminal regions, which contain putative nuclear localization signals; swapping the C-terminal region between maternal and zygotic genes diminishes the developmental defects. This study suggests that evolutionary diversification has occurred in MCM3 genes, leading to distinct functions, possibly as an adaption to the rapid DNA replication required for early development of Xenopus and zebrafish.
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Affiliation(s)
- Minori Shinya
- a Genetic Strains Research Center; National Institute of Genetics ; Mishima , Shizuoka , Japan
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24
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Das M, Prasad SB, Yadav SS, Modi A, Singh S, Pradhan S, Narayan G. HPV-type-specific response of cervical cancer cells to cisplatin after silencing replication licensing factor MCM4. Tumour Biol 2015; 36:9987-94. [PMID: 26188903 DOI: 10.1007/s13277-015-3782-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 07/08/2015] [Indexed: 12/25/2022] Open
Abstract
Minichoromosome maintenance (MCM) proteins play key role in cell cycle progression by licensing DNA replication only once per cell cycle. These proteins are found to be overexpressed in cervical cancer cells. In this study, we depleted MCM4, one of the MCM 2-7 complex components by RNA interference (RNAi) in four cervical cancer cell lines. The four cell lines were selected on the basis of their human papillomavirus (HPV) infection: HPV16-positive SiHa, HPV18-positive ME-180, HPV16- and HPV18-positive CaSki, and HPV-negative C-33A. The MCM4-deficient cells irrespective of their HPV status grow for several generations and maintain regular cell cycle. We did not find any evidence of augmented response to a short-term (48 h) cisplatin treatment in these MCM4-deficient cells. However, MCM4-/HPV16+ SiHa cells cannot withstand a prolonged treatment (up to 5 days) of even a sublethal dosage of cisplatin. They show increased chromosomal instability compared to their control counterparts. On the other hand, MCM4-deficient CaSki cells (both HPV16+ and 18+) remain resistant to a prolonged exposure to cisplatin. Our study indicates that cervical cancer cells may be using excess MCMs as a backup for replicative stress; however, its regulatory mechanism is dependent on the HPV status of the cells.
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Affiliation(s)
- Mitali Das
- Cancer Genetics Laboratory, Department of Molecular and Human Genetics, Banaras Hindu University, Varanasi, 221 005, Uttar Pradesh, India
| | - Shyam Babu Prasad
- Cancer Genetics Laboratory, Department of Molecular and Human Genetics, Banaras Hindu University, Varanasi, 221 005, Uttar Pradesh, India.,Division of Molecular Oncology, Institute of Cytology and Preventive Oncology, I-7, Sector-39, Noida, 201 301, India
| | - Suresh Singh Yadav
- Cancer Genetics Laboratory, Department of Molecular and Human Genetics, Banaras Hindu University, Varanasi, 221 005, Uttar Pradesh, India
| | - Arusha Modi
- Cancer Genetics Laboratory, Department of Molecular and Human Genetics, Banaras Hindu University, Varanasi, 221 005, Uttar Pradesh, India
| | - Sunita Singh
- Department of Zoology, Mahila Mahavidyalaya, Banaras Hindu University, Varanasi, 221 005, Uttar Pradesh, India
| | - Satyajit Pradhan
- Department of Radiotherapy and Radiation Medicine, Banaras Hindu University, Varanasi, 221 005, Uttar Pradesh, India
| | - Gopeshwar Narayan
- Cancer Genetics Laboratory, Department of Molecular and Human Genetics, Banaras Hindu University, Varanasi, 221 005, Uttar Pradesh, India.
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25
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Suchyta M, Miotto B, McGarry TJ. An inactive geminin mutant that binds cdt1. Genes (Basel) 2015; 6:252-66. [PMID: 25988259 PMCID: PMC4488664 DOI: 10.3390/genes6020252] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 04/24/2015] [Accepted: 04/28/2015] [Indexed: 12/27/2022] Open
Abstract
The initiation of DNA replication is tightly regulated in order to ensure that the genome duplicates only once per cell cycle. In vertebrate cells, the unstable regulatory protein Geminin prevents a second round of DNA replication by inhibiting the essential replication factor Cdt1. Cdt1 recruits mini-chromosome maintenance complex (MCM2-7), the replication helicase, into the pre-replication complex (pre-RC) at origins of DNA replication. The mechanism by which Geminin inhibits MCM2-7 loading by Cdt1 is incompletely understood. The conventional model is that Geminin sterically hinders a direct physical interaction between Cdt1 and MCM2-7. Here, we describe an inactive missense mutant of Geminin, GemininAWA, which binds to Cdt1 with normal affinity yet is completely inactive as a replication inhibitor even when added in vast excess. In fact, GemininAWA can compete with GemininWT for binding to Cdt1 and prevent it from inhibiting DNA replication. GemininAWA does not inhibit the loading of MCM2-7 onto DNA in vivo, and in the presence of GemininAWA, nuclear DNA is massively over-replicated within a single S phase. We conclude that Geminin does not inhibit MCM loading by simple steric interference with a Cdt1-MCM2-7 interaction but instead works by a non-steric mechanism, possibly by inhibiting the histone acetyltransferase HBO1.
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Affiliation(s)
- Marissa Suchyta
- Department of Medicine, Feinberg Cardiovascular Research Institute, Feinberg School of Medicine, Northwestern University Chicago, IL 60610, USA.
| | - Benoit Miotto
- Epigenetics and Cell Fate, Sorbonne Paris Cité, University Paris Diderot, UMR 7216 CNRS, Paris 75013, France.
| | - Thomas J McGarry
- Department of Medicine, Feinberg Cardiovascular Research Institute, Feinberg School of Medicine, Northwestern University Chicago, IL 60610, USA.
- George Wahlen Veterans Affairs Medical Center, Room 2E 24, 500 Foothill Drive, Salt Lake City, UT 84103, USA.
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26
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Powell SK, MacAlpine HK, Prinz JA, Li Y, Belsky JA, MacAlpine DM. Dynamic loading and redistribution of the Mcm2-7 helicase complex through the cell cycle. EMBO J 2015; 34:531-43. [PMID: 25555795 DOI: 10.15252/embj.201488307] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Eukaryotic replication origins are defined by the ORC-dependent loading of the Mcm2-7 helicase complex onto chromatin in G1. Paradoxically, there is a vast excess of Mcm2-7 relative to ORC assembled onto chromatin in G1. These excess Mcm2-7 complexes exhibit little co-localization with ORC or replication foci and can function as dormant origins. We dissected the mechanisms regulating the assembly and distribution of the Mcm2-7 complex in the Drosophila genome. We found that in the absence of cyclin E/Cdk2 activity, there was a 10-fold decrease in chromatin-associated Mcm2-7 relative to the levels found at the G1/S transition. The minimal amounts of Mcm2-7 loaded in the absence of cyclin E/Cdk2 activity were strictly localized to ORC binding sites. In contrast, cyclin E/Cdk2 activity was required for maximal loading of Mcm2-7 and a dramatic genome-wide reorganization of the distribution of Mcm2-7 that is shaped by active transcription. Thus, increasing cyclin E/Cdk2 activity over the course of G1 is not only critical for Mcm2-7 loading, but also for the distribution of the Mcm2-7 helicase prior to S-phase entry.
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Affiliation(s)
- Sara K Powell
- Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Heather K MacAlpine
- Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Joseph A Prinz
- Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Yulong Li
- Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Jason A Belsky
- Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - David M MacAlpine
- Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
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27
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MCM Paradox: Abundance of Eukaryotic Replicative Helicases and Genomic Integrity. Mol Biol Int 2014; 2014:574850. [PMID: 25386362 PMCID: PMC4217321 DOI: 10.1155/2014/574850] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 09/30/2014] [Indexed: 12/03/2022] Open
Abstract
As a crucial component of DNA replication licensing system, minichromosome maintenance (MCM) 2–7 complex acts as the eukaryotic DNA replicative helicase. The six related MCM proteins form a heterohexamer and bind with ORC, CDC6, and Cdt1 to form the prereplication complex. Although the MCMs are well known as replicative helicases, their overabundance and distribution patterns on chromatin present a paradox called the “MCM paradox.” Several approaches had been taken to solve the MCM paradox and describe the purpose of excess MCMs distributed beyond the replication origins. Alternative functions of these MCMs rather than a helicase had also been proposed. This review focuses on several models and concepts generated to solve the MCM paradox coinciding with their helicase function and provides insight into the concept that excess MCMs are meant for licensing dormant origins as a backup during replication stress. Finally, we extend our view towards the effect of alteration of MCM level. Though an excess MCM constituent is needed for normal cells to withstand stress, there must be a delineation of the threshold level in normal and malignant cells. This review also outlooks the future prospects to better understand the MCM biology.
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28
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Alver RC, Chadha GS, Blow JJ. The contribution of dormant origins to genome stability: from cell biology to human genetics. DNA Repair (Amst) 2014; 19:182-9. [PMID: 24767947 PMCID: PMC4065331 DOI: 10.1016/j.dnarep.2014.03.012] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The ability of a eukaryotic cell to precisely and accurately replicate its DNA is crucial to maintain genome stability. Here we describe our current understanding of the process by which origins are licensed for DNA replication and review recent work suggesting that fork stalling has exerted a strong selective pressure on the positioning of licensed origins. In light of this, we discuss the complex and disparate phenotypes observed in mouse models and humans patients that arise due to defects in replication licensing proteins.
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Affiliation(s)
- Robert C Alver
- Centre for Gene Regulation & Expression, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
| | - Gaganmeet Singh Chadha
- Centre for Gene Regulation & Expression, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
| | - J Julian Blow
- Centre for Gene Regulation & Expression, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK.
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