1
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Cui J, Liu X, Shang Q, Sun S, Chen S, Dong J, Zhu Y, Liu L, Xia Y, Wang Y, Xiang L, Fan B, Zhan J, Zhou Y, Chen P, Zhao R, Liu X, Xing N, Wu D, Shi B, Zou Y. Deubiquitination of CDC6 by OTUD6A promotes tumour progression and chemoresistance. Mol Cancer 2024; 23:86. [PMID: 38685067 PMCID: PMC11057083 DOI: 10.1186/s12943-024-01996-y] [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: 12/04/2023] [Accepted: 04/05/2024] [Indexed: 05/02/2024] Open
Abstract
BACKGROUND CDC6 is an oncogenic protein whose expression level fluctuates during the cell cycle. Although several E3 ubiquitin ligases responsible for the ubiquitin-mediated proteolysis of CDC6 have been identified, the deubiquitination pathway for CDC6 has not been investigated. METHODS The proteome-wide deubiquitinase (DUB) screening was used to identify the potential regulator of CDC6. Immunofluorescence, protein half-life and deubiquitination assays were performed to determine the protein stability of CDC6. Gain- and loss-of-function experiments were implemented to analyse the impacts of OUTD6A-CDC6 axis on tumour growth and chemosensitivity in vitro. N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN)-induced conditional Otud6a knockout (CKO) mouse model and tumour xenograft model were performed to analyse the role of OTUD6A-CDC6 axis in vivo. Tissue specimens were used to determine the association between OTUD6A and CDC6. RESULTS OTUD6A interacts with, depolyubiquitinates and stabilizes CDC6 by removing K6-, K33-, and K48-linked polyubiquitination. Moreover, OTUD6A promotes cell proliferation and decreases sensitivity to chemotherapy by upregulating CDC6. CKO mice are less prone to BCa tumorigenesis induced by BBN, and knockdown of OTUD6A inhibits tumour progression in vivo. Furthermore, OTUD6A protein level has a positive correlation with CDC6 protein level, and high protein levels of OTUD6A and CDC6 are associated with poor prognosis in patients with bladder cancer. CONCLUSIONS We reveal an important yet missing piece of novel DUB governing CDC6 stability. In addition, our findings propose a model for the OTUD6A-CDC6 axis that provides novel insights into cell cycle and chemosensitivity regulation, which may become a potential biomarker and promising drug target for cancer treatment.
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Affiliation(s)
- Jianfeng Cui
- Department of Urology, Qilu Hospital, Department of Molecular Medicine and Genetics, School of Basic Medical Sciences, Shandong University, Jinan, Shandong, 250012, China
- The Key Laboratory of Experimental Teratology, Ministry of Education and Department of Molecular Medicine and Genetics, School of Basic Medical Sciences, Qilu Hospital, Shandong University, Jinan, Shandong, 250012, China
| | - Xiaochen Liu
- The Key Laboratory of Experimental Teratology, Ministry of Education and Department of Molecular Medicine and Genetics, School of Basic Medical Sciences, Qilu Hospital, Shandong University, Jinan, Shandong, 250012, China
- Department of Clinical laboratory, Qilu Hospital, Shandong University, Jinan, Shandong, 250012, China
| | - Qinghong Shang
- Helmholtz International Lab, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, Shandong, 266237, China
| | - Shuna Sun
- Department of Dermatology, The Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Shandong Provincial Hospital of Traditional Chinese Medicine, Jinan, Shandong, 250011, China
| | - Shouzhen Chen
- Department of Urology, Qilu Hospital, Department of Molecular Medicine and Genetics, School of Basic Medical Sciences, Shandong University, Jinan, Shandong, 250012, China
| | - Jianping Dong
- Department of Urology, Shouguang People's Hospital, Weifang, Shandong, 262750, China
| | - Yaofeng Zhu
- Department of Urology, Qilu Hospital, Department of Molecular Medicine and Genetics, School of Basic Medical Sciences, Shandong University, Jinan, Shandong, 250012, China
| | - Lei Liu
- Department of Urology, Qilu Hospital, Department of Molecular Medicine and Genetics, School of Basic Medical Sciences, Shandong University, Jinan, Shandong, 250012, China
| | - Yangyang Xia
- Department of Urology, Qilu Hospital, Department of Molecular Medicine and Genetics, School of Basic Medical Sciences, Shandong University, Jinan, Shandong, 250012, China
| | - Yong Wang
- Department of Urology, Qilu Hospital, Department of Molecular Medicine and Genetics, School of Basic Medical Sciences, Shandong University, Jinan, Shandong, 250012, China
| | - Lu Xiang
- The Key Laboratory of Experimental Teratology, Ministry of Education and Department of Molecular Medicine and Genetics, School of Basic Medical Sciences, Qilu Hospital, Shandong University, Jinan, Shandong, 250012, China
| | - Bowen Fan
- The Key Laboratory of Experimental Teratology, Ministry of Education and Department of Molecular Medicine and Genetics, School of Basic Medical Sciences, Qilu Hospital, Shandong University, Jinan, Shandong, 250012, China
| | - Jiafeng Zhan
- The Key Laboratory of Experimental Teratology, Ministry of Education and Department of Molecular Medicine and Genetics, School of Basic Medical Sciences, Qilu Hospital, Shandong University, Jinan, Shandong, 250012, China
| | - Yadi Zhou
- The Key Laboratory of Experimental Teratology, Ministry of Education and Department of Molecular Medicine and Genetics, School of Basic Medical Sciences, Qilu Hospital, Shandong University, Jinan, Shandong, 250012, China
| | - Pengxiang Chen
- Department of Radiation Oncology, Qilu Hospital, Shandong University, Jinan, Shandong, 250012, China
| | - Renchang Zhao
- Department of Thoracic Surgery, Qilu Hospital, Shandong University, Jinan, Shandong, 250012, China
| | - Xiaofei Liu
- Departement of Breast and Thyroid Surgery, The Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Shandong Provincial Hospital of Traditional Chinese Medicine, Jinan, Shandong, 250011, China
| | - Nianzeng Xing
- Department of Urology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100021, China.
| | - Dalei Wu
- Helmholtz International Lab, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, Shandong, 266237, China.
| | - Benkang Shi
- Department of Urology, Qilu Hospital, Department of Molecular Medicine and Genetics, School of Basic Medical Sciences, Shandong University, Jinan, Shandong, 250012, China.
| | - Yongxin Zou
- The Key Laboratory of Experimental Teratology, Ministry of Education and Department of Molecular Medicine and Genetics, School of Basic Medical Sciences, Qilu Hospital, Shandong University, Jinan, Shandong, 250012, China.
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2
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Liu D, Sonalkar J, Prasanth SG. ORChestra coordinates the replication and repair music. Bioessays 2023; 45:e2200229. [PMID: 36811379 PMCID: PMC10023367 DOI: 10.1002/bies.202200229] [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: 11/29/2022] [Revised: 02/03/2023] [Accepted: 02/06/2023] [Indexed: 02/24/2023]
Abstract
Error-free genome duplication and accurate cell division are critical for cell survival. In all three domains of life, bacteria, archaea, and eukaryotes, initiator proteins bind replication origins in an ATP-dependent manner, play critical roles in replisome assembly, and coordinate cell-cycle regulation. We discuss how the eukaryotic initiator, Origin recognition complex (ORC), coordinates different events during the cell cycle. We propose that ORC is the maestro driving the orchestra to coordinately perform the musical pieces of replication, chromatin organization, and repair.
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Affiliation(s)
- Dazhen Liu
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601S Goodwin Avenue, Urbana, IL 61801 USA
| | - Jay Sonalkar
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601S Goodwin Avenue, Urbana, IL 61801 USA
| | - Supriya G. Prasanth
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601S Goodwin Avenue, Urbana, IL 61801 USA
- Cancer center at Illinois, UIUC
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3
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Reusswig KU, Bittmann J, Peritore M, Courtes M, Pardo B, Wierer M, Mann M, Pfander B. Unscheduled DNA replication in G1 causes genome instability and damage signatures indicative of replication collisions. Nat Commun 2022; 13:7014. [PMID: 36400763 PMCID: PMC9674678 DOI: 10.1038/s41467-022-34379-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 10/24/2022] [Indexed: 11/19/2022] Open
Abstract
DNA replicates once per cell cycle. Interfering with the regulation of DNA replication initiation generates genome instability through over-replication and has been linked to early stages of cancer development. Here, we engineer genetic systems in budding yeast to induce unscheduled replication in a G1-like cell cycle state. Unscheduled G1 replication initiates at canonical S-phase origins. We quantifiy the composition of replisomes in G1- and S-phase and identified firing factors, polymerase α, and histone supply as factors that limit replication outside S-phase. G1 replication per se does not trigger cellular checkpoints. Subsequent replication during S-phase, however, results in over-replication and leads to chromosome breaks and chromosome-wide, strand-biased occurrence of RPA-bound single-stranded DNA, indicating head-to-tail replication collisions as a key mechanism generating genome instability upon G1 replication. Low-level, sporadic induction of G1 replication induces an identical response, indicating findings from synthetic systems are applicable to naturally occurring scenarios of unscheduled replication initiation.
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Affiliation(s)
- Karl-Uwe Reusswig
- grid.418615.f0000 0004 0491 845XDNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ,grid.38142.3c000000041936754XPresent Address: Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA 02115 USA ,grid.65499.370000 0001 2106 9910Present Address: Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA 02215 USA
| | - Julia Bittmann
- grid.418615.f0000 0004 0491 845XDNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Martina Peritore
- grid.418615.f0000 0004 0491 845XDNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ,grid.7551.60000 0000 8983 7915Present Address: Genome Maintenance Mechanisms in Health and Disease, Institute of Aerospace Medicine, German Aerospace Center (DLR), 51147 Cologne, Germany
| | - Mathilde Courtes
- grid.433120.7Institut de Génétique Humaine (IGH), Université de Montpellier – Centre National de la Recherche Scientifique, 34396 Montpellier, France
| | - Benjamin Pardo
- grid.433120.7Institut de Génétique Humaine (IGH), Université de Montpellier – Centre National de la Recherche Scientifique, 34396 Montpellier, France
| | - Michael Wierer
- grid.418615.f0000 0004 0491 845XProteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ,grid.5254.60000 0001 0674 042XPresent Address: Proteomics Research Infrastructure, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Matthias Mann
- grid.418615.f0000 0004 0491 845XProteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Boris Pfander
- grid.418615.f0000 0004 0491 845XDNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ,grid.7551.60000 0000 8983 7915Present Address: Genome Maintenance Mechanisms in Health and Disease, Institute of Aerospace Medicine, German Aerospace Center (DLR), 51147 Cologne, Germany ,grid.6190.e0000 0000 8580 3777Present Address: Genome Maintenance Mechanisms in Health and Disease, Institute of Genome Stability in Ageing and Disease, CECAD Research Center, University of Cologne, 50931 Cologne, Germany
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4
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A Temporary Pause in the Replication Licensing Restriction Leads to Rereplication during Early Human Cell Differentiation. Cells 2022; 11:cells11061060. [PMID: 35326512 PMCID: PMC8946923 DOI: 10.3390/cells11061060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 03/18/2022] [Accepted: 03/20/2022] [Indexed: 12/10/2022] Open
Abstract
Gene amplifications in amphibians and flies are known to occur during development and have been well characterized, unlike in mammalian cells, where they are predominantly investigated as an attribute of tumors. Recently, we first described gene amplifications in human and mouse neural stem cells, myoblasts, and mesenchymal stem cells during differentiation. The mechanism leading to gene amplifications in amphibians and flies depends on endocycles and multiple origin-firings. So far, there is no knowledge about a comparable mechanism in normal human cells. Here, we describe rereplication during the early myotube differentiation of human skeletal myoblast cells, using fiber combing and pulse-treatment with EdU (5′-Ethynyl-2′-deoxyuridine)/CldU (5-Chlor-2′-deoxyuridine) and IdU (5-Iodo-2′-deoxyuridine)/CldU. We found rereplication during a restricted time window between 2 h and 8 h after differentiation induction. Rereplication was detected in cells simultaneously with the amplification of the MDM2 gene. Our findings support rereplication as a mechanism enabling gene amplification in normal human cells.
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5
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Wenmaekers S, Viergever BJ, Kumar G, Kranenburg O, Black PC, Daugaard M, Meijer RP. A Potential Role for HUWE1 in Modulating Cisplatin Sensitivity. Cells 2021; 10:cells10051262. [PMID: 34065298 PMCID: PMC8160634 DOI: 10.3390/cells10051262] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 05/17/2021] [Accepted: 05/18/2021] [Indexed: 12/25/2022] Open
Abstract
Cisplatin is a widely used antineoplastic agent, whose efficacy is limited by primary and acquired therapeutic resistance. Recently, a bladder cancer genome-wide CRISPR/Cas9 knock-out screen correlated cisplatin sensitivity to multiple genetic biomarkers. Among the screen’s top hits was the HECT domain-containing ubiquitin E3 ligase (HUWE1). In this review, HUWE1 is postulated as a therapeutic response modulator, affecting the collision between platinum-DNA adducts and the replication fork, the primary cytotoxic action of platins. HUWE1 can alter the cytotoxic response to platins by targeting essential components of the DNA damage response including BRCA1, p53, and Mcl-1. Deficiency of HUWE1 could lead to enhanced DNA damage repair and a dysfunctional apoptotic apparatus, thereby inducing resistance to platins. Future research on the relationship between HUWE1 and platins could generate new mechanistic insights into therapy resistance. Ultimately, HUWE1 might serve as a clinical biomarker to tailor cancer treatment strategies, thereby improving cancer care and patient outcomes.
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Affiliation(s)
- Stijn Wenmaekers
- Laboratory Translational Oncology, University Medical Center Utrecht, 3584CX Utrecht, The Netherlands; (S.W.); (B.J.V.); (O.K.)
- Department of Oncological Urology, University Medical Center Utrecht, 3584CX Utrecht, The Netherlands
| | - Bastiaan J. Viergever
- Laboratory Translational Oncology, University Medical Center Utrecht, 3584CX Utrecht, The Netherlands; (S.W.); (B.J.V.); (O.K.)
- Department of Oncological Urology, University Medical Center Utrecht, 3584CX Utrecht, The Netherlands
| | - Gunjan Kumar
- Department of Urologic Sciences, University of British Columbia, Vancouver, BC V5Z 1M9, Canada; (G.K.); (P.C.B.)
- Vancouver Prostate Centre, Vancouver, BC V6H 3Z6, Canada
| | - Onno Kranenburg
- Laboratory Translational Oncology, University Medical Center Utrecht, 3584CX Utrecht, The Netherlands; (S.W.); (B.J.V.); (O.K.)
| | - Peter C. Black
- Department of Urologic Sciences, University of British Columbia, Vancouver, BC V5Z 1M9, Canada; (G.K.); (P.C.B.)
- Vancouver Prostate Centre, Vancouver, BC V6H 3Z6, Canada
| | - Mads Daugaard
- Department of Urologic Sciences, University of British Columbia, Vancouver, BC V5Z 1M9, Canada; (G.K.); (P.C.B.)
- Vancouver Prostate Centre, Vancouver, BC V6H 3Z6, Canada
- Correspondence: (M.D.); (R.P.M.)
| | - Richard P. Meijer
- Laboratory Translational Oncology, University Medical Center Utrecht, 3584CX Utrecht, The Netherlands; (S.W.); (B.J.V.); (O.K.)
- Department of Oncological Urology, University Medical Center Utrecht, 3584CX Utrecht, The Netherlands
- Correspondence: (M.D.); (R.P.M.)
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6
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Cyclin E2 Promotes Whole Genome Doubling in Breast Cancer. Cancers (Basel) 2020; 12:cancers12082268. [PMID: 32823571 PMCID: PMC7463708 DOI: 10.3390/cancers12082268] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Revised: 08/02/2020] [Accepted: 08/04/2020] [Indexed: 11/21/2022] Open
Abstract
Genome doubling is an underlying cause of cancer cell aneuploidy and genomic instability, but few drivers have been identified for this process. Due to their physiological roles in the genome reduplication of normal cells, we hypothesised that the oncogenes cyclins E1 and E2 may be drivers of genome doubling in cancer. We show that both cyclin E1 (CCNE1) and cyclin E2 (CCNE2) mRNA are significantly associated with high genome ploidy in breast cancers. By live cell imaging and flow cytometry, we show that cyclin E2 overexpression promotes aberrant mitosis without causing mitotic slippage, and it increases ploidy with negative feedback on the replication licensing protein, Cdt1. We demonstrate that cyclin E2 localises with core preRC (pre-replication complex) proteins (MCM2, MCM7) on the chromatin of cancer cells. Low CCNE2 is associated with improved overall survival in breast cancers, and we demonstrate that low cyclin E2 protects from excess genome rereplication. This occurs regardless of p53 status, consistent with the association of high cyclin E2 with genome doubling in both p53 null/mutant and p53 wildtype cancers. In contrast, while cyclin E1 can localise to the preRC, its downregulation does not prevent rereplication, and overexpression promotes polyploidy via mitotic slippage. Thus, in breast cancer, cyclin E2 has a strong association with genome doubling, and likely contributes to highly proliferative and genomically unstable breast cancers.
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7
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Grant GD, Kedziora KM, Limas JC, Cook JG, Purvis JE. Accurate delineation of cell cycle phase transitions in living cells with PIP-FUCCI. Cell Cycle 2019; 17:2496-2516. [PMID: 30421640 DOI: 10.1080/15384101.2018.1547001] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Cell cycle phase transitions are tightly orchestrated to ensure efficient cell cycle progression and genome stability. Interrogating these transitions is important for understanding both normal and pathological cell proliferation. By quantifying the dynamics of the popular FUCCI reporters relative to the transitions into and out of S phase, we found that their dynamics are substantially and variably offset from true S phase boundaries. To enhance detection of phase transitions, we generated a new reporter whose oscillations are directly coupled to DNA replication and combined it with the FUCCI APC/C reporter to create "PIP-FUCCI". The PIP degron fusion protein precisely marks the G1/S and S/G2 transitions; shows a rapid decrease in signal in response to large doses of DNA damage only during G1; and distinguishes cell type-specific and DNA damage source-dependent arrest phenotypes. We provide guidance to investigators in selecting appropriate fluorescent cell cycle reporters and new analysis strategies for delineating cell cycle transitions.
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Affiliation(s)
- Gavin D Grant
- a Department of Biochemistry and Biophysics , The University of North Carolina , Chapel Hill , NC , USA.,b Lineberger Comprehensive Cancer Center , The University of North Carolina , Chapel Hill , NC , USA
| | - Katarzyna M Kedziora
- c Department of Genetics , The University of North Carolina , Chapel Hill , NC , USA
| | - Juanita C Limas
- d Department of Pharmacology , The University of North Carolina , Chapel Hill , NC , USA
| | - Jeanette Gowen Cook
- a Department of Biochemistry and Biophysics , The University of North Carolina , Chapel Hill , NC , USA.,b Lineberger Comprehensive Cancer Center , The University of North Carolina , Chapel Hill , NC , USA.,d Department of Pharmacology , The University of North Carolina , Chapel Hill , NC , USA
| | - Jeremy E Purvis
- b Lineberger Comprehensive Cancer Center , The University of North Carolina , Chapel Hill , NC , USA.,c Department of Genetics , The University of North Carolina , Chapel Hill , NC , USA
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8
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Tsao WC, Eckert KA. Detours to Replication: Functions of Specialized DNA Polymerases during Oncogene-induced Replication Stress. Int J Mol Sci 2018; 19:ijms19103255. [PMID: 30347795 PMCID: PMC6214091 DOI: 10.3390/ijms19103255] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2018] [Revised: 10/15/2018] [Accepted: 10/15/2018] [Indexed: 01/10/2023] Open
Abstract
Incomplete and low-fidelity genome duplication contribute to genomic instability and cancer development. Difficult-to-Replicate Sequences, or DiToRS, are natural impediments in the genome that require specialized DNA polymerases and repair pathways to complete and maintain faithful DNA synthesis. DiToRS include non B-DNA secondary structures formed by repetitive sequences, for example within chromosomal fragile sites and telomeres, which inhibit DNA replication under endogenous stress conditions. Oncogene activation alters DNA replication dynamics and creates oncogenic replication stress, resulting in persistent activation of the DNA damage and replication stress responses, cell cycle arrest, and cell death. The response to oncogenic replication stress is highly complex and must be tightly regulated to prevent mutations and tumorigenesis. In this review, we summarize types of known DiToRS and the experimental evidence supporting replication inhibition, with a focus on the specialized DNA polymerases utilized to cope with these obstacles. In addition, we discuss different causes of oncogenic replication stress and its impact on DiToRS stability. We highlight recent findings regarding the regulation of DNA polymerases during oncogenic replication stress and the implications for cancer development.
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Affiliation(s)
- Wei-Chung Tsao
- Department of Pathology, The Jake Gittlen Laboratories for Cancer Research, Hershey, PA 17033, USA.
| | - Kristin A Eckert
- Department of Pathology, The Jake Gittlen Laboratories for Cancer Research, Hershey, PA 17033, USA.
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9
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Pozo PN, Matson JP, Cole Y, Kedziora KM, Grant GD, Temple B, Cook JG. Cdt1 variants reveal unanticipated aspects of interactions with cyclin/CDK and MCM important for normal genome replication. Mol Biol Cell 2018; 29:2989-3002. [PMID: 30281379 PMCID: PMC6333176 DOI: 10.1091/mbc.e18-04-0242] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The earliest step in DNA replication is origin licensing, which is the DNA loading of minichromosome maintenance (MCM) helicase complexes. The Cdc10-dependent transcript 1 (Cdt1) protein is essential for MCM loading during the G1 phase of the cell cycle, but the mechanism of Cdt1 function is still incompletely understood. We examined a collection of rare Cdt1 variants that cause a form of primordial dwarfism (the Meier-Gorlin syndrome) plus one hypomorphic Drosophila allele to shed light on Cdt1 function. Three hypomorphic variants load MCM less efficiently than wild-type (WT) Cdt1, and their lower activity correlates with impaired MCM binding. A structural homology model of the human Cdt1-MCM complex positions the altered Cdt1 residues at two distinct interfaces rather than the previously described single MCM interaction domain. Surprisingly, one dwarfism allele (Cdt1-A66T) is more active than WT Cdt1. This hypermorphic variant binds both cyclin A and SCFSkp2 poorly relative to WT Cdt1. Detailed quantitative live-cell imaging analysis demonstrated no change in the stability of this variant, however. Instead, we propose that cyclin A/CDK inhibits the Cdt1 licensing function independent of the creation of the SCFSkp2 phosphodegron. Together, these findings identify key Cdt1 interactions required for both efficient origin licensing and tight Cdt1 regulation to ensure normal cell proliferation and genome stability.
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Affiliation(s)
- Pedro N Pozo
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Jacob P Matson
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Yasemin Cole
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Katarzyna M Kedziora
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Gavin D Grant
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599.,Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Brenda Temple
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599.,R. L. Juliano Structural Bioinformatics Core Facility, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599.,Center for Structural Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Jeanette Gowen Cook
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599.,Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599.,Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
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10
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Yanku Y, Bitman-Lotan E, Zohar Y, Kurant E, Zilke N, Eilers M, Orian A. Drosophila HUWE1 Ubiquitin Ligase Regulates Endoreplication and Antagonizes JNK Signaling During Salivary Gland Development. Cells 2018; 7:E151. [PMID: 30261639 PMCID: PMC6210797 DOI: 10.3390/cells7100151] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 09/20/2018] [Accepted: 09/21/2018] [Indexed: 01/18/2023] Open
Abstract
The HECT-type ubiquitin ligase HECT, UBA and WWE Domain Containing 1, (HUWE1) regulates key cancer-related pathways, including the Myc oncogene. It affects cell proliferation, stress and immune signaling, mitochondria homeostasis, and cell death. HUWE1 is evolutionarily conserved from Caenorhabditis elegance to Drosophila melanogaster and Humans. Here, we report that the Drosophila ortholog, dHUWE1 (CG8184), is an essential gene whose loss results in embryonic lethality and whose tissue-specific disruption establishes its regulatory role in larval salivary gland development. dHUWE1 is essential for endoreplication of salivary gland cells and its knockdown results in the inability of these cells to replicate DNA. Remarkably, dHUWE1 is a survival factor that prevents premature activation of JNK signaling, thus preventing the disintegration of the salivary gland, which occurs physiologically during pupal stages. This function of dHUWE1 is general, as its inhibitory effect is observed also during eye development and at the organismal level. Epistatic studies revealed that the loss of dHUWE1 is compensated by dMyc proeitn expression or the loss of dmP53. dHUWE1 is therefore a conserved survival factor that regulates organ formation during Drosophila development.
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Affiliation(s)
- Yifat Yanku
- Rappaport Research Faculty of Medicine, Technion-Israel Institute of Technology, Haifa 31096, Israel.
| | - Eliya Bitman-Lotan
- Rappaport Research Faculty of Medicine, Technion-Israel Institute of Technology, Haifa 31096, Israel.
| | - Yaniv Zohar
- Rappaport Research Faculty of Medicine, Technion-Israel Institute of Technology, Haifa 31096, Israel.
- Institute of Pathology, RAMBAM Medical Center, Haifa 30196, Israel.
| | - Estee Kurant
- Faculty of Natural Sciences, University of Haifa, Haifa 3498838, Israel.
| | - Norman Zilke
- Genome-Scale Biology Research Program Institute of Biomedicine University of Helsinki, 00290 Helsinki, Finland.
| | - Martin Eilers
- Theodor Boveri Institute, Biocenter, University of Würzburg, D-97074 Würzburg, Germany.
| | - Amir Orian
- Rappaport Research Faculty of Medicine, Technion-Israel Institute of Technology, Haifa 31096, Israel.
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11
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Yuan Y, Ma XS, Liang QX, Xu ZY, Huang L, Meng TG, Lin F, Schatten H, Wang ZB, Sun QY. Geminin deletion in pre-meiotic DNA replication stage causes spermatogenesis defect and infertility. J Reprod Dev 2017; 63:481-488. [PMID: 28690291 PMCID: PMC5649097 DOI: 10.1262/jrd.2017-036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Geminin plays a critical role in cell cycle regulation by regulating DNA replication and serves as a transcriptional molecular switch that directs cell fate decisions. Spermatogonia lacking Geminin disappear
during the initial wave of mitotic proliferation, while geminin is not required for meiotic progression of spermatocytes. It is unclear whether geminin plays a role in pre-meiotic DNA replication in later-stage spermatogonia and
their subsequent differentiation. Here, we selectively disrupted Geminin in the male germline using the Stra8-Cre/loxP conditional knockout system.
Geminin-deficient mice showed atrophic testes and infertility, concomitant with impaired spermatogenesis and reduced sperm motility. The number of undifferentiated spermatogonia and spermatocytes was significantly
reduced; the pachytene stage was impaired most severely. Expression of cell proliferation-associated genes was reduced in Gmnnfl/Δ; Stra8-Cre testes compared to in controls. Increased
DNA damage, decreased Cdt1, and increased phosphorylation of Chk1/Chk2 were observed in Geminin-deficient germ cells. These results suggest that geminin plays important roles in pre-meiotic DNA replication and
subsequent spermatogenesis.
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Affiliation(s)
- Yue Yuan
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing 100101, China
| | - Xue-Shan Ma
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.,The Reproductive Medical Center, the First Affiliated Hospital, Zhengzhou University, Zhengzhou 450052, China
| | - Qiu-Xia Liang
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Zhao-Yang Xu
- The Reproductive Medical Center, the First Affiliated Hospital, Zhengzhou University, Zhengzhou 450052, China
| | - Lin Huang
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Tie-Gang Meng
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing 100101, China
| | - Fei Lin
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Heide Schatten
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA
| | - Zhen-Bo Wang
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing 100101, China
| | - Qing-Yuan Sun
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing 100101, China
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12
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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: 65] [Impact Index Per Article: 8.1] [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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13
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Choe KN, Nicolae CM, Constantin D, Imamura Kawasawa Y, Delgado-Diaz MR, De S, Freire R, Smits VA, Moldovan GL. HUWE1 interacts with PCNA to alleviate replication stress. EMBO Rep 2016; 17:874-86. [PMID: 27146073 DOI: 10.15252/embr.201541685] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 04/05/2016] [Indexed: 02/01/2023] Open
Abstract
Defects in DNA replication, DNA damage response, and DNA repair compromise genomic stability and promote cancer development. In particular, unrepaired DNA lesions can arrest the progression of the DNA replication machinery during S-phase, causing replication stress, mutations, and DNA breaks. HUWE1 is a HECT-type ubiquitin ligase that targets proteins involved in cell fate, survival, and differentiation. Here, we report that HUWE1 is essential for genomic stability, by promoting replication of damaged DNA We show that HUWE1-knockout cells are unable to mitigate replication stress, resulting in replication defects and DNA breakage. Importantly, we find that this novel role of HUWE1 requires its interaction with the replication factor PCNA, a master regulator of replication fork restart, at stalled replication forks. Finally, we provide evidence that HUWE1 mono-ubiquitinates H2AX to promote signaling at stalled forks. Altogether, our work identifies HUWE1 as a novel regulator of the replication stress response.
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Affiliation(s)
- Katherine N Choe
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA, USA
| | - Claudia M Nicolae
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA, USA
| | - Daniel Constantin
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA, USA
| | - Yuka Imamura Kawasawa
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA, USA Department of Pharmacology, The Pennsylvania State University College of Medicine, Hershey, PA, USA Institute for Personalized Medicine, The Pennsylvania State University College of Medicine, Hershey, PA, USA
| | - Maria Rocio Delgado-Diaz
- Unidad de Investigación, Hospital Universitario de Canarias, Instituto de Tecnologías Biomédicas, La Laguna Tenerife, Spain
| | - Subhajyoti De
- Department of Medicine, University of Colorado School of Medicine, Aurora, CO, USA Department of Biostatistics and Informatics, Colorado School of Public Health, Aurora, CO, USA Molecular Oncology Program, University of Colorado Cancer Center, Aurora, CO, USA
| | - Raimundo Freire
- Unidad de Investigación, Hospital Universitario de Canarias, Instituto de Tecnologías Biomédicas, La Laguna Tenerife, Spain
| | - Veronique Aj Smits
- Unidad de Investigación, Hospital Universitario de Canarias, Instituto de Tecnologías Biomédicas, La Laguna Tenerife, Spain
| | - George-Lucian Moldovan
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA, USA
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14
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Zielke N, Edgar BA. FUCCI sensors: powerful new tools for analysis of cell proliferation. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2015; 4:469-87. [PMID: 25827130 PMCID: PMC6681141 DOI: 10.1002/wdev.189] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 02/11/2015] [Accepted: 02/26/2015] [Indexed: 01/09/2023]
Abstract
Visualizing the cell cycle behavior of individual cells within living organisms can facilitate the understanding of developmental processes such as pattern formation, morphogenesis, cell differentiation, growth, cell migration, and cell death. Fluorescence Ubiquitin Cell Cycle Indicator (FUCCI) technology offers an accurate, versatile, and universally applicable means of achieving this end. In recent years, the FUCCI system has been adapted to several model systems including flies, fish, mice, and plants, making this technology available to a wide range of researchers for studies of diverse biological problems. Moreover, a broad range of FUCCI‐expressing cell lines originating from diverse cell types have been generated, hence enabling the design of advanced studies that combine in vivo experiments and cell‐based methods such as high‐content screening. Although only a short time has passed since its introduction, the FUCCI technology has already provided fundamental insight into how cells establish quiescence and how G1 phase length impacts the balance between pluripotency and stem cell differentiation. Further discoveries using the FUCCI technology are sure to come. WIREs Dev Biol 2015, 4:469–487. doi: 10.1002/wdev.189 This article is categorized under:
Adult Stem Cells, Tissue Renewal, and Regeneration > Methods and Principles Technologies > Generating Chimeras and Lineage Analysis Technologies > Analysis of Cell, Tissue, and Animal Phenotypes
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Affiliation(s)
- N Zielke
- Deutsches Krebsforschungszentrum (DKFZ), Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH) Allianz, Heidelberg, Germany
| | - B A Edgar
- Deutsches Krebsforschungszentrum (DKFZ), Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH) Allianz, Heidelberg, Germany
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15
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Rizzardi LF, Coleman KE, Varma D, Matson JP, Oh S, Cook JG. CDK1-dependent inhibition of the E3 ubiquitin ligase CRL4CDT2 ensures robust transition from S Phase to Mitosis. J Biol Chem 2014; 290:556-67. [PMID: 25411249 DOI: 10.1074/jbc.m114.614701] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Replication-coupled destruction of a cohort of cell cycle proteins ensures efficient and precise genome duplication. Three proteins destroyed during replication via the CRL4(CDT2) ubiquitin E3 ligase, CDT1, p21, and SET8 (PR-SET7), are also essential or important during mitosis, making their reaccumulation after S phase a critical cell cycle event. During early and mid-S phase and during DNA repair, proliferating cell nuclear antigen (PCNA) loading onto DNA (PCNA(DNA)) triggers the interaction between CRL4(CDT2) and its substrates, resulting in their degradation. We have discovered that, beginning in late S phase, PCNA(DNA) is no longer sufficient to trigger CRL4(CDT2)-mediated degradation. A CDK1-dependent mechanism that blocks CRL4(CDT2) activity by interfering with CDT2 recruitment to chromatin actively protects CRL4(CDT2) substrates. We postulate that deliberate override of replication-coupled destruction allows anticipatory accumulation in late S phase. We further show that (as for CDT1) de novo SET8 reaccumulation is important for normal mitotic progression. In this manner, CDK1-dependent CRL4(CDT2) inactivation contributes to efficient transition from S phase to mitosis.
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Affiliation(s)
| | - Kate E Coleman
- From the Curriculum in Genetics and Molecular Biology and
| | - Dileep Varma
- the Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Jacob P Matson
- the Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Seeun Oh
- the Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Jeanette Gowen Cook
- From the Curriculum in Genetics and Molecular Biology and the Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599
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16
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Lv L, Li Y, Deng H, Zhang C, Pu Y, Qian L, Xiao J, Zhao W, Liu Q, Zhang D, Wang Y, Zhang H, He Y, Zhu J. MiR-193a-3p promotes the multi-chemoresistance of bladder cancer by targeting the HOXC9 gene. Cancer Lett 2014; 357:105-113. [PMID: 25444900 DOI: 10.1016/j.canlet.2014.11.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 11/03/2014] [Accepted: 11/04/2014] [Indexed: 01/15/2023]
Abstract
Chemoresistance prevents the curative cancer chemotherapy and presents a formidable challenge for both cancer researchers and clinicians. We have previously shown that miR-193a-3p promotes the multi-chemoresistance of bladder cancer cells via repressing its three target genes: SRSF2, PLAU and HIC2. Here, we showed that as a new direct target, the homeobox C9 (HOXC9) gene also executes the promoting effect of miR-193a-3p on the bladder cancer chemoresistance from a systematic study of multi-chemosensitive (5637) and resistant (H-bc) bladder cancer cell lines in both cell culture and tumor-xenograft/nude mice system. Paralleled with the changes in the drug-triggered cell death, the activities of both DNA damage response and oxidative stress pathways were drastically altered by a forced reversal of miR-193a-3p or HOXC9 levels in bladder cancer cells. In addition to a new mechanistic insight, our results provide a set of the essential genes in the miR-193a-3p/HOXC9/DNA damage response/oxidative stress pathway axis as the diagnostic targets for the guided anti-bladder cancer chemotherapy.
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Affiliation(s)
- Lei Lv
- Cancer Epigenetics Program, Anhui Cancer Hospital, Hefei, Anhui 230031, China
| | - Yang Li
- Department of Biology, School of Life Science, Anhui Medical University, Hefei, Anhui 230031, China
| | - Hui Deng
- Cancer Epigenetics Program, Anhui Cancer Hospital, Hefei, Anhui 230031, China
| | - Cheng Zhang
- Department of Urology, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang Province, China
| | - Youguang Pu
- Cancer Epigenetics Program, Anhui Cancer Hospital, Hefei, Anhui 230031, China
| | - Liting Qian
- Department of Radiotherapy, Anhui Cancer Hospital, Hefei, Anhui 230031, China
| | - Jun Xiao
- Department of Urology, Anhui Provincial Hospital, Hefei, Anhui, China
| | - Weidong Zhao
- Department of Gynecologic Cancer, Anhui Cancer Hospital, Hefei, Anhui 230031, China
| | - Qi Liu
- School of Life Science and Technology, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China
| | - Daming Zhang
- Department of Neurosurgery, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang Province, China
| | - Yingwei Wang
- Department of Pathology, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang Province, China
| | - Hongyu Zhang
- Cancer Epigenetics Program, Shanghai Cancer Institute, Renji Hospital, Shanghai Jiaotong University, Shanghai 200032, China
| | - Yinghua He
- Cancer Epigenetics Program, Shanghai Cancer Institute, Renji Hospital, Shanghai Jiaotong University, Shanghai 200032, China
| | - Jingde Zhu
- Cancer Epigenetics Program, Anhui Cancer Hospital, Hefei, Anhui 230031, China; Cancer Epigenetics Program, Shanghai Cancer Institute, Renji Hospital, Shanghai Jiaotong University, Shanghai 200032, China.
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17
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Iwakura T, Fujigaki Y, Fujikura T, Ohashi N, Kato A, Yasuda H. A high ratio of G1 to G0 phase cells and an accumulation of G1 phase cells before S phase progression after injurious stimuli in the proximal tubule. Physiol Rep 2014; 2:e12173. [PMID: 25293601 PMCID: PMC4254098 DOI: 10.14814/phy2.12173] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 09/09/2014] [Accepted: 09/10/2014] [Indexed: 12/25/2022] Open
Abstract
Proximal tubule (PT) cells can proliferate explosively after injurious stimuli. To investigate this proliferative capacity, we examined cell cycle status and the expression of cyclin-dependent kinase inhibitor p27, a G1 phase mediator, in PT cells after a proliferative or injurious stimulus. Rats were treated with lead acetate (proliferative stimulus) or uranyl acetate (UA; injurious stimulus). Isolated tubular cells were separated into PT and distal tubule (DT) cells by density-gradient centrifugation. Cell cycle status was analyzed with flow cytometry by using the Hoechst 33342/pyronin Y method. Most PT and DT cells from control rats were in G0/G1 phase, with a higher percentage of PT cells than DT cells in G1 phase. Lead acetate and UA administration promoted the G0-G1 transition and the accumulation of G1 phase cells before S phase progression. In PT cells from rats treated with lead acetate or a subnephrotoxic dose of UA, p27 levels increased or did not change, possibly reflecting G1 arrest. In contrast, p27 became undetectable before the appearance of apoptotic cells in rats treated with a nephrotoxic dose of UA. The decrease in p27 might facilitate rapid cell cycling. The decreased number of p27-positive cells was associated with PT cell proliferation in renal tissues after a proliferative or injurious stimulus. The findings suggest that a high ratio of G1 to G0 phase cells and a rapid accumulation of G1 phase cells before S phase progression in the PT is a biological strategy for safe, timely, and explosive cell proliferation in response to injurious stimuli.
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Affiliation(s)
- Takamasa Iwakura
- Internal Medicine I, Division of Nephrology, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Yoshihide Fujigaki
- Internal Medicine I, Division of Nephrology, Hamamatsu University School of Medicine, Hamamatsu, Japan
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Tomoyuki Fujikura
- Internal Medicine I, Division of Nephrology, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Naro Ohashi
- Internal Medicine I, Division of Nephrology, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Akihiko Kato
- Blood Purification Unit, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Hideo Yasuda
- Internal Medicine I, Division of Nephrology, Hamamatsu University School of Medicine, Hamamatsu, Japan
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18
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14-3-3 proteins play a role in the cell cycle by shielding cdt2 from ubiquitin-mediated degradation. Mol Cell Biol 2014; 34:4049-61. [PMID: 25154416 DOI: 10.1128/mcb.00838-14] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cdt2 is the substrate recognition adaptor of CRL4(Cdt2) E3 ubiquitin ligase complex and plays a pivotal role in the cell cycle by mediating the proteasomal degradation of Cdt1 (DNA replication licensing factor), p21 (cyclin-dependent kinase [CDK] inhibitor), and Set8 (histone methyltransferase) in S phase. Cdt2 itself is attenuated by SCF(FbxO11)-mediated proteasomal degradation. Here, we report that 14-3-3 adaptor proteins interact with Cdt2 phosphorylated at threonine 464 (T464) and shield it from polyubiquitination and consequent proteasomal degradation. Depletion of 14-3-3 proteins promotes the interaction of FbxO11 with Cdt2. Overexpressing 14-3-3 proteins shields Cdt2 that has a phospho-mimicking mutation (T464D [change of T to D at position 464]) but not Cdt2(T464A) from ubiquitination. Furthermore, the delay of the cell cycle in the G2/M phase and decrease in cell proliferation seen upon depletion of 14-3-3γ is partly due to the accumulation of the CRL4(Cdt2) substrate, Set8 methyltransferase. Therefore, the stabilization of Cdt2 is an important function of 14-3-3 proteins in cell cycle progression.
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19
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A spontaneous Cdt1 mutation in 129 mouse strains reveals a regulatory domain restraining replication licensing. Nat Commun 2013; 4:2065. [PMID: 23817338 DOI: 10.1038/ncomms3065] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Accepted: 05/29/2013] [Indexed: 12/25/2022] Open
Abstract
Cdt1 is required for loading the replicative DNA helicase MCM2/7, a process known as DNA replication licensing. Here we show that 129 mouse strains express a Cdt1 mutated allele with enhanced licensing activity. The mutation, named Δ(6)PEST, involves a six-amino acid deletion within a previously uncharacterized PEST-like domain. Cdt1 Δ(6)PEST and more extensive deletions exhibit increased re-replication and transformation activities that are independent of the Geminin and E3 ligase pathways. This PEST domain negatively regulates cell cycle-dependent chromatin recruitment of Cdt1 in G2/M phases of the cell cycle. Mass spectrometry analysis indicates that Cdt1 is phosphorylated at sites within the deleted PEST domain during mitosis. This study reveals a conserved new regulatory Cdt1 domain crucial for proper DNA licensing activity and suggests a mechanism by which the presence of Cdt1 in G2/M phases does not lead to premature origin licensing. These results also question the usage of 129 mouse strains for knockout analyses.
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20
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Aurora-A controls pre-replicative complex assembly and DNA replication by stabilizing geminin in mitosis. Nat Commun 2013; 4:1885. [PMID: 23695679 PMCID: PMC3675325 DOI: 10.1038/ncomms2859] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 04/10/2013] [Indexed: 01/14/2023] Open
Abstract
Geminin, an essential factor for DNA replication, directly binds to the licensing factor Cdt1 and inhibits pre-replicative complex formation to prevent re-replication. In G1, geminin levels are controlled by the anaphase-promoting complex/cyclosome (APC/C) ubiquitin ligase complex, which targets geminin for proteasomal degradation to allow pre-replicative complex formation. Conversely, from S to G2, geminin is stabilized due to APC/C ubiquitin ligase complex inhibition, ensuring the inhibition of pre-replicative complex formation. However, mitotic regulation of geminin has hitherto not been described. Here we show that Aurora-A phosphorylates geminin on Thr25 during M phase, and this event induces geminin stabilization by preventing its APC/C ubiquitin ligase complex-mediated degradation during mitosis. In turn, stabilized geminin inhibits SCFSkp2-mediated degradation of Cdt1 to ensure pre-replicative complex formation in the ensuing S phase. The Aurora-A–geminin–Cdt1 axis therefore represents a critical regulator of proper DNA replication. Geminin blocks the inappropriate assembly of pre-replication complexes on DNA, and this activity is inhibited in G1 by its proteasomal degradation. Tsunematsu et al. demonstrate that geminin is stabilized during mitosis due to its phosphorylation by the mitotic kinase Aurora-A.
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21
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Geminin deploys multiple mechanisms to regulate Cdt1 before cell division thus ensuring the proper execution of DNA replication. Proc Natl Acad Sci U S A 2013; 110:E2848-53. [PMID: 23836640 DOI: 10.1073/pnas.1310677110] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Cdc10-dependent transcript 1 (Cdt1) is an essential DNA replication protein whose accumulation at the end of the cell cycle promotes the formation of pre-replicative complexes and replication in the next cell cycle. Geminin is thought to be involved in licensing replication by promoting the accumulation of Cdt1 in mitosis, because decreasing the Geminin levels prevents Cdt1 accumulation and impairs DNA replication. Geminin is known to inhibit Cdt1 function; its depletion during G2 leads to DNA rereplication and checkpoint activation. Here we show that, despite rapid Cdt1 protein turnover in G2 phase, Geminin promotes Cdt1 accumulation by increasing its RNA and protein levels in the unperturbed cell cycle. Therefore, Geminin is a master regulator of cell-cycle progression that ensures the timely onset of DNA replication and prevents its rereplication.
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22
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Clijsters L, Ogink J, Wolthuis R. The spindle checkpoint, APC/C(Cdc20), and APC/C(Cdh1) play distinct roles in connecting mitosis to S phase. ACTA ACUST UNITED AC 2013; 201:1013-26. [PMID: 23775192 PMCID: PMC3691463 DOI: 10.1083/jcb.201211019] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The spindle checkpoint, APC/C-Cdc20, and APC/C-Cdh1 act successively to connect disappearance of geminin and cyclin B1 to a peak of Cdt1 and Cdc6. DNA replication depends on a preceding licensing event by Cdt1 and Cdc6. In animal cells, relicensing after S phase but before mitosis is prevented by the Cdt1 inhibitor geminin and mitotic cyclin activity. Here, we show that geminin, like cyclin B1 and securin, is a bona fide target of the spindle checkpoint and APC/CCdc20. Cyclin B1 and geminin are degraded simultaneously during metaphase, which directs Cdt1 accumulation on segregating sister chromatids. Subsequent activation of APC/CCdh1 leads to degradation of Cdc6 well before Cdt1 becomes unstable in a replication-coupled manner. In mitosis, the spindle checkpoint supports Cdt1 accumulation, which promotes S phase onset. We conclude that the spindle checkpoint, APC/CCdc20, and APC/CCdh1 act successively to ensure that the disappearance of licensing inhibitors coincides exactly with a peak of Cdt1 and Cdc6. Whereas cell cycle entry from quiescence requires Cdc6 resynthesis, our results indicate that proliferating cells use a window of time in mitosis, before Cdc6 is degraded, as an earlier opportunity to direct S phase.
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Affiliation(s)
- Linda Clijsters
- Division of Cell Biology I (B5), The Netherlands Cancer Institute (NKI-AvL), 1066 CX Amsterdam, Netherlands.
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23
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Chen X, Liu G, Leffak M. Activation of a human chromosomal replication origin by protein tethering. Nucleic Acids Res 2013; 41:6460-74. [PMID: 23658226 PMCID: PMC3711443 DOI: 10.1093/nar/gkt368] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The specification of mammalian chromosomal replication origins is incompletely understood. To analyze the assembly and activation of prereplicative complexes (pre-RCs), we tested the effects of tethered binding of chromatin acetyltransferases and replication proteins on chromosomal c-myc origin deletion mutants containing a GAL4-binding cassette. GAL4DBD (DNA binding domain) fusions with Orc2, Cdt1, E2F1 or HBO1 coordinated the recruitment of the Mcm7 helicase subunit, the DNA unwinding element (DUE)-binding protein DUE-B and the minichromosome maintenance (MCM) helicase activator Cdc45 to the replicator, and restored origin activity. In contrast, replication protein binding and origin activity were not stimulated by fusion protein binding in the absence of flanking c-myc DNA. Substitution of the GAL4-binding site for the c-myc replicator DUE allowed Orc2 and Mcm7 binding, but eliminated origin activity, indicating that the DUE is essential for pre-RC activation. Additionally, tethering of DUE-B was not sufficient to recruit Cdc45 or activate pre-RCs formed in the absence of a DUE. These results show directly in a chromosomal background that chromatin acetylation, Orc2 or Cdt1 suffice to recruit all downstream replication initiation activities to a prospective origin, and that chromosomal origin activity requires singular DNA sequences.
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Affiliation(s)
- Xiaomi Chen
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435, USA
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24
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Abstract
The cell cycle ensures genome maintenance by coordinating the processes of DNA replication and chromosome segregation. Of particular importance is the irreversible transition from the G1 phase of the cell cycle to S phase. This transition marks the switch from preparing chromosomes for replication ("origin licensing") to active DNA synthesis ("origin firing"). Ubiquitin-mediated proteolysis is essential for restricting DNA replication to only once per cell cycle and is the major mechanism regulating the G1 to S phase transition. Although some changes in protein levels are attributable to regulated mRNA abundance, protein degradation elicits very rapid changes in protein abundance and is critical for the sharp and irreversible transition from one cell cycle stage to the next. Not surprisingly, regulation of the G1-to-S phase transition is perturbed in most cancer cells, and deregulation of key molecular events in G1 and S phase drives not only cell proliferation but also genome instability. In this review we focus on the mechanisms by which E3 ubiquitin ligases control the irreversible transition from G1 to S phase in mammalian cells.
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Affiliation(s)
- Lindsay F Rizzardi
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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Dai Y, Chen S, Kmieciak M, Zhou L, Lin H, Pei XY, Grant S. The novel Chk1 inhibitor MK-8776 sensitizes human leukemia cells to HDAC inhibitors by targeting the intra-S checkpoint and DNA replication and repair. Mol Cancer Ther 2013; 12:878-89. [PMID: 23536721 DOI: 10.1158/1535-7163.mct-12-0902] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Interactions between the novel Chk1 inhibitor MK-8776 and the histone deacetylase (HDAC) inhibitor (HDACI) vorinostat were examined in human leukemia cells harboring wild-type (wt) or deficient p53. MK-8776 synergistically potentiated vorinostat-mediated apoptosis in various p53-wt or -deficient leukemia cell lines, whereas p53 knockdown by short hairpin RNA (shRNA) sensitized p53-wt cells to lethality of this regimen. Leukemia cell lines carrying FLT3-ITD were also sensitive to the MK-8776/vorinostat regimen. Synergistic interactions were associated with inhibition of Chk1 activity, interference with the intra-S-phase checkpoint, disruption of DNA replication, and downregulation of proteins involved in DNA replication (e.g., Cdt1) and repair (e.g., CtIP and BRCA1), resulting in sharp increases in DNA damage, reflected by enhanced γ-H2A.X formation, and apoptosis. Moreover, leukemia cells expressing kinase-dead Chk1 (D130A) or Chk1 shRNA were significantly more sensitive to HDACIs compared with their wt counterparts and displayed downregulation of CtIP and BRCA1 phosphorylation following HDACI exposure. Finally, the MK-8776/vorinostat regimen was active in primary acute myelogenous leukemia (AML) blasts, particularly against the CD34(+)/CD38(-)/CD123(+) population enriched for leukemia-initiating cells. In contrast, identical regimens were relatively sparing toward normal cord blood CD34(+) cells. Together, these findings indicate that the novel Chk1 inhibitor MK-8776 markedly potentiates HDACI lethality in leukemia cells displaying various genetic backgrounds through mechanisms involving disruption of the intra-S checkpoint, DNA replication, and DNA repair. They also argue that leukemic cells, including those bearing oncogenic mutations associated with poor prognosis, for example, p53 deletion/mutation or FLT3-ITD, may also be susceptible to this strategy.
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Affiliation(s)
- Yun Dai
- Division of Hematology/Oncology, Department of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
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Kim DH, Zhang W, Koepp DM. The Hect domain E3 ligase Tom1 and the F-box protein Dia2 control Cdc6 degradation in G1 phase. J Biol Chem 2012; 287:44212-20. [PMID: 23129771 DOI: 10.1074/jbc.m112.401778] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The accurate replication of genetic information is critical to maintaining chromosomal integrity. Cdc6 functions in the assembly of pre-replicative complexes and is specifically required to load the Mcm2-7 replicative helicase complex at replication origins. Cdc6 is targeted for protein degradation by multiple mechanisms in Saccharomyces cerevisiae, although only a single pathway and E3 ubiquitin ligase for Cdc6 has been identified, the SCF(Cdc4) (Skp1/Cdc53/F-box protein) complex. Notably, Cdc6 is unstable during the G(1) phase of the cell cycle, but the ubiquitination pathway has not been previously identified. Using a genetic approach, we identified two additional E3 ubiquitin ligase components required for Cdc6 degradation, the F-box protein Dia2 and the Hect domain E3 Tom1. Both Dia2 and Tom1 control Cdc6 turnover during G(1) phase of the cell cycle and act separately from SCF(Cdc4). Ubiquitination of Cdc6 is significantly reduced in dia2Δ and tom1Δ cells. Tom1 and Dia2 each independently immunoprecipitate Cdc6, binding to a C-terminal region of the protein. Tom1 and Dia2 cannot compensate for each other in Cdc6 degradation. Cdc6 and Mcm4 chromatin association is aberrant in tom1Δ and dia2Δ cells in G(1) phase. Together, these results present evidence for a novel degradation pathway that controls Cdc6 turnover in G(1) that may regulate pre-replicative complex assembly.
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Affiliation(s)
- Dong-Hwan Kim
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Klotz-Noack K, McIntosh D, Schurch N, Pratt N, Blow JJ. Re-replication induced by geminin depletion occurs from G2 and is enhanced by checkpoint activation. J Cell Sci 2012; 125:2436-45. [PMID: 22366459 PMCID: PMC3481538 DOI: 10.1242/jcs.100883] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To prevent re-replication of DNA in a single cell cycle, the licensing of replication origins by Mcm2-7 is prevented during S and G2 phases. Animal cells achieve this by cell-cycle-regulated proteolysis of the essential licensing factor Cdt1 and inhibition of Cdt1 by geminin. Here we investigate the consequences of ablating geminin in synchronised human U2OS cells. Following geminin loss, cells complete an apparently normal S phase, but a proportion arrest at the G2-M boundary. When Cdt1 accumulates in these cells, DNA re-replicates, suggesting that the key role of geminin is to prevent re-licensing in G2. If cell cycle checkpoints are inhibited in cells lacking geminin, cells progress through mitosis and less re-replication occurs. Checkpoint kinases thereby amplify re-replication into an all-or-nothing response by delaying geminin-depleted cells in G2. Deep DNA sequencing revealed no preferential re-replication of specific genomic regions after geminin depletion. This is consistent with the observation that cells in G2 have lost their replication timing information. By contrast, when Cdt1 is overexpressed or is stabilised by the neddylation inhibitor MLN4924, re-replication can occur throughout S phase.
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Affiliation(s)
- Kathleen Klotz-Noack
- Wellcome Trust Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| | - Debbie McIntosh
- Wellcome Trust Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| | - Nicholas Schurch
- Data Analysis Group, College of Life Sciences, University of Dundee DD1 5EH, UK
| | - Norman Pratt
- Department of Human Genetics, Ninewells Hospital, Dundee DD1 9SY, UK
| | - J. Julian Blow
- Wellcome Trust Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
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Stress-stimulated mitogen-activated protein kinases control the stability and activity of the Cdt1 DNA replication licensing factor. Mol Cell Biol 2011; 31:4405-16. [PMID: 21930785 DOI: 10.1128/mcb.06163-11] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
DNA replication is tightly coordinated both with cell cycle cues and with responses to extracellular signals to maintain genome stability. We discovered that human Cdt1, an essential origin licensing protein whose activity must be restricted to G(1) phase, is a substrate of the stress-activated mitogen-activated protein (MAP) kinases p38 and c-Jun N-terminal kinase (JNK). These MAP kinases phosphorylate Cdt1 both during unperturbed G(2) phase and during an acute stress response. Phosphorylation renders Cdt1 resistant to ubiquitin-mediated degradation during S phase and after DNA damage by blocking Cdt1 binding to the Cul4 adaptor, Cdt2. Mutations that block normal cell cycle-regulated MAP kinase-mediated phosphorylation interfere with rapid Cdt1 reaccumulation at the end of S phase. Phosphomimetic mutations recapitulate the stabilizing effects of Cdt1 phosphorylation but also reduce the ability of Cdt1 to support origin licensing. Two other CRL4(Cdt2) targets, the cyclin-dependent kinase (CDK) inhibitor p21 and the methyltransferase PR-Set7/Set8, are similarly stabilized by MAP kinase activity. These findings support a model in which MAP kinase activity in G(2) promotes reaccumulation of a low-activity Cdt1 isoform after replication is complete.
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29
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Abstract
DNA replication is a highly regulated process involving a number of licensing and replication factors that function in a carefully orchestrated manner to faithfully replicate DNA during every cell cycle. Loss of proper licensing control leads to deregulated DNA replication including DNA re-replication, which can cause genome instability and tumorigenesis. Eukaryotic organisms have established several conserved mechanisms to prevent DNA re-replication and to counteract its potentially harmful effects. These mechanisms include tightly controlled regulation of licensing factors and activation of cell cycle and DNA damage checkpoints. Deregulated licensing control and its associated compromised checkpoints have both been observed in tumor cells, indicating that proper functioning of these pathways is essential for maintaining genome stability. In this review, we discuss the regulatory mechanisms of licensing control, the deleterious consequences when both licensing and checkpoints are compromised, and present possible mechanisms to prevent re-replication in order to maintain genome stability.
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Affiliation(s)
- Lan N Truong
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
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30
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Davidson JM, Duronio RJ. Using Drosophila S2 cells to measure S phase-coupled protein destruction via flow cytometry. Methods Mol Biol 2011; 782:205-219. [PMID: 21870294 DOI: 10.1007/978-1-61779-273-1_15] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Cell proliferation depends on the timely synthesis and destruction of proteins at specific phases of the cell cycle. Recently it was discovered that the destruction of several key cell cycle regulatory proteins during S phase is coupled directly to DNA replication. These proteins harbor a motif called a PIP degron that mediates binding to chromatin bound PCNA at replication forks and recruits the CRL4(Cdt2) E3 ubiquitin ligase. These interactions comprise an elegant mechanism for coupling DNA replication with ubiquitylation and subsequent proteolysis by the 26S proteasome. Here we describe a flow cytometry-based method using Drosophila S2 cells that recapitulates S phase-specific protein proteolysis. Because of the high degree of evolutionary conservation of the PIP degron and CRL4(Cdt2) and the ease of culturing and inhibiting gene function by RNAi in S2 cells, our flow cytometric method should serve as a general tool for determining whether any eukaryotic protein is subject to replication-coupled protein destruction.
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Affiliation(s)
- Jean M Davidson
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA.
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31
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Ding Q, MacAlpine DM. Preferential re-replication of Drosophila heterochromatin in the absence of geminin. PLoS Genet 2010; 6:e1001112. [PMID: 20838463 PMCID: PMC2936543 DOI: 10.1371/journal.pgen.1001112] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Accepted: 08/05/2010] [Indexed: 01/04/2023] Open
Abstract
To ensure genomic integrity, the genome must be duplicated exactly once per cell cycle. Disruption of replication licensing mechanisms may lead to re-replication and genomic instability. Cdt1, also known as Double-parked (Dup) in Drosophila, is a key regulator of the assembly of the pre-replicative complex (pre-RC) and its activity is strictly limited to G1 by multiple mechanisms including Cul4-Ddb1 mediated proteolysis and inhibition by geminin. We assayed the genomic consequences of disregulating the replication licensing mechanisms by RNAi depletion of geminin. We found that not all origins of replication were sensitive to geminin depletion and that heterochromatic sequences were preferentially re-replicated in the absence of licensing mechanisms. The preferential re-activation of heterochromatic origins of replication was unexpected because these are typically the last sequences to be duplicated in a normal cell cycle. We found that the re-replication of heterochromatin was regulated not at the level of pre-RC activation, but rather by the formation of the pre-RC. Unlike the global assembly of the pre-RC that occurs throughout the genome in G1, in the absence of geminin, limited pre-RC assembly was restricted to the heterochromatin by elevated cyclin A-CDK activity. These results suggest that there are chromatin and cell cycle specific controls that regulate the re-assembly of the pre-RC outside of G1. Catastrophic consequences may occur if the cell fails to either completely copy the genome or if it duplicates some regions of the genome more than once in a cell cycle. The cell must coordinate thousands of DNA replication start sites (origins) to ensure that the entire genome is copied and that no replication origin is activated more than once in a cell cycle. The cell accomplishes this coordination by confining the selection and activation of replication origins to discrete phases of the cell cycle. Start sites can only be selected or ‘licensed’ for DNA replication in G1 and similarly, they can only be activated for the initiation of DNA replication in S phase. Disruption of the mechanisms that regulate this ‘licensing’ process have been shown to result in extensive re-replication, genomic instability and tumorigenesis in a variety of eukaryotic systems. Here we use genomic approaches in Drosophila to identify which origins of replication are susceptible to re-initiation of DNA replication in the absence of replication licensing controls. Unexpectedly, we find that sequences in the heterochromatin, which were thought to contain only inefficient origins of replication, are preferentially re-replicated. These results provide insights into how origins of replication are selected and regulated in distinct chromatin environments to maintain genomic stability.
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Affiliation(s)
- Queying Ding
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - David M. MacAlpine
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina, United States of America
- * E-mail:
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32
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Lee HO, Zacharek SJ, Xiong Y, Duronio RJ. Cell type-dependent requirement for PIP box-regulated Cdt1 destruction during S phase. Mol Biol Cell 2010; 21:3639-53. [PMID: 20826610 PMCID: PMC2965682 DOI: 10.1091/mbc.e10-02-0130] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Previous studies have shown that Cdt1 overexpression in cultured cells can trigger re-replication, but not whether CRL4Cdt2-triggered destruction of Cdt1 is required for normal mitotic cell cycle progression in vivo. We demonstrate that PIP box–mediated destruction of Cdt1Dup during S phase is necessary for the cell division cycle in Drosophila. DNA synthesis–coupled proteolysis of the prereplicative complex component Cdt1 by the CRL4Cdt2 E3 ubiquitin ligase is thought to help prevent rereplication of the genome during S phase. To directly test whether CRL4Cdt2-triggered destruction of Cdt1 is required for normal cell cycle progression in vivo, we expressed a mutant version of Drosophila Cdt1 (Dup), which lacks the PCNA-binding PIP box (DupΔPIP) and which cannot be regulated by CRL4Cdt2. DupΔPIP is inappropriately stabilized during S phase and causes developmental defects when ectopically expressed. DupΔPIP restores DNA synthesis to dup null mutant embryonic epidermal cells, but S phase is abnormal, and these cells do not progress into mitosis. In contrast, DupΔPIP accumulation during S phase did not adversely affect progression through follicle cell endocycles in the ovary. In this tissue the combination of DupΔPIP expression and a 50% reduction in Geminin gene dose resulted in egg chamber degeneration. We could not detect Dup hyperaccumulation using mutations in the CRL4Cdt2 components Cul4 and Ddb1, likely because these cause pleiotropic effects that block cell proliferation. These data indicate that PIP box–mediated destruction of Dup is necessary for the cell division cycle and suggest that Geminin inhibition can restrain DupΔPIP activity in some endocycling cell types.
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Affiliation(s)
- Hyun O Lee
- Curriculum in Genetics and Molecular Biology, Department of Biochemistry and Biophysics, Lineberger Comprehensive Cancer Center, and Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, NC 27599, USA
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Li G, Park HU, Liang D, Zhao RY. Cell cycle G2/M arrest through an S phase-dependent mechanism by HIV-1 viral protein R. Retrovirology 2010; 7:59. [PMID: 20609246 PMCID: PMC2909154 DOI: 10.1186/1742-4690-7-59] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2010] [Accepted: 07/07/2010] [Indexed: 01/23/2023] Open
Abstract
Background Cell cycle G2 arrest induced by HIV-1 Vpr is thought to benefit viral proliferation by providing an optimized cellular environment for viral replication and by skipping host immune responses. Even though Vpr-induced G2 arrest has been studied extensively, how Vpr triggers G2 arrest remains elusive. Results To examine this initiation event, we measured the Vpr effect over a single cell cycle. We found that even though Vpr stops the cell cycle at the G2/M phase, but the initiation event actually occurs in the S phase of the cell cycle. Specifically, Vpr triggers activation of Chk1 through Ser345 phosphorylation in an S phase-dependent manner. The S phase-dependent requirement of Chk1-Ser345 phosphorylation by Vpr was confirmed by siRNA gene silencing and site-directed mutagenesis. Moreover, downregulation of DNA replication licensing factors Cdt1 by siRNA significantly reduced Vpr-induced Chk1-Ser345 phosphorylation and G2 arrest. Even though hydroxyurea (HU) and ultraviolet light (UV) also induce Chk1-Ser345 phosphorylation in S phase under the same conditions, neither HU nor UV-treated cells were able to pass through S phase, whereas vpr-expressing cells completed S phase and stopped at the G2/M boundary. Furthermore, unlike HU/UV, Vpr promotes Chk1- and proteasome-mediated protein degradations of Cdc25B/C for G2 induction; in contrast, Vpr had little or no effect on Cdc25A protein degradation normally mediated by HU/UV. Conclusions These data suggest that Vpr induces cell cycle G2 arrest through a unique molecular mechanism that regulates host cell cycle regulation in an S-phase dependent fashion.
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Affiliation(s)
- Ge Li
- Department of Pathology, Institute of Human Virology, University of Maryland School of Medicine, Baltimore, MD, USA
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Ma HT, Tsang YH, Marxer M, Poon RYC. Cyclin A2-cyclin-dependent kinase 2 cooperates with the PLK1-SCFbeta-TrCP1-EMI1-anaphase-promoting complex/cyclosome axis to promote genome reduplication in the absence of mitosis. Mol Cell Biol 2009; 29:6500-14. [PMID: 19822658 PMCID: PMC2786869 DOI: 10.1128/mcb.00669-09] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2009] [Revised: 07/13/2009] [Accepted: 10/06/2009] [Indexed: 12/22/2022] Open
Abstract
Limiting genome replication to once per cell cycle is vital for maintaining genome stability. Inhibition of cyclin-dependent kinase 1 (CDK1) with the specific inhibitor RO3306 is sufficient to trigger multiple rounds of genome reduplication. We demonstrated that although anaphase-promoting complex/cyclosome (APC/C) remained inactive during the initial G(2) arrest, it was activated upon prolonged inhibition of CDK1. Using cellular biosensors and live-cell imaging, we provide direct evidence that genome reduplication was associated with oscillation of APC/C activity and nuclear-cytoplasmic shuttling of CDC6 even in the absence of mitosis at the single-cell level. Genome reduplication was abolished by ectopic expression of EMI1 or depletion of CDC20 or CDH1, suggesting the critical role of the EMI1-APC/C axis. In support of this, degradation of EMI1 itself and genome reduplication were delayed after downregulation of PLK1 and beta-TrCP1. In the absence of CDK1 activity, activation of APC/C and genome reduplication was dependent on cyclin A2 and CDK2. Genome reduplication was then promoted by a combination of APC/C-dependent destruction of geminin (thus releasing CDT1), accumulation of cyclin E2-CDK2, and CDC6. Collectively, these results underscore the crucial role of cyclin A2-CDK2 in regulating the PLK1-SCF(beta-TrCP1)-EMI1-APC/C axis and CDC6 to trigger genome reduplication after the activity of CDK1 is suppressed.
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Affiliation(s)
- Hoi Tang Ma
- Department of Biochemistry, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong.
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35
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Rampakakis E, Arvanitis DN, Di Paola D, Zannis-Hadjopoulos M. Metazoan origins of DNA replication: regulation through dynamic chromatin structure. J Cell Biochem 2009; 106:512-20. [PMID: 19173303 DOI: 10.1002/jcb.22070] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
DNA replication in eukaryotes is initiated at multiple replication origins distributed over the entire genome, which are normally activated once per cell cycle. Due to the complexity of the metazoan genome, the study of metazoan replication origins and their activity profiles has been less advanced than in simpler genome systems. DNA replication in eukaryotes involves many protein-protein and protein-DNA interactions, occurring in multiple stages. As in prokaryotes, control over the timing and frequency of initiation is exerted at the initiation site. A prerequisite for understanding the regulatory mechanisms of eukaryotic DNA replication is the identification and characterization of the cis-acting sequences that serve as replication origins and the trans-acting factors (proteins) that interact with them. Furthermore, in order to understand how DNA replication may become deregulated in malignant cells, the distinguishing features between normal and malignant origins of DNA replication as well as the proteins that interact with them must be determined. Based on advances that were made using simple genome model systems, several proteins involved in DNA replication have been identified. This review summarizes the current findings about metazoan origins of DNA replication and their interacting proteins as well as the role of chromatin structure in their regulation. Furthermore, progress in origin identification and isolation procedures as well as potential mechanisms to inhibit their activation in cancer development and progression are discussed.
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Affiliation(s)
- E Rampakakis
- Department of Biochemistry, Goodman Cancer Centre, Montreal, Quebec, Canada
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36
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Cook JG. Replication licensing and the DNA damage checkpoint. Front Biosci (Landmark Ed) 2009; 14:5013-30. [PMID: 19482602 DOI: 10.2741/3584] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Accurate and timely duplication of chromosomal DNA requires that replication be coordinated with processes that ensure genome integrity. Significant advances in determining how the earliest steps in DNA replication are affected by DNA damage have highlighted some of the mechanisms to establish that coordination. Recent insights have expanded the relationship between the ATM and ATR-dependent checkpoint pathways and the proteins that bind and function at replication origins. These findings suggest that checkpoints and replication are more intimately associated than previously appreciated, even in the absence of exogenous DNA damage. This review summarizes some of these developments.
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Affiliation(s)
- Jeanette Gowen Cook
- Department of Biochemistry and Biophysics, Lineberger Comprehensive Cancer Center Campus Box 7260, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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37
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Dorn ES, Chastain PD, Hall JR, Cook JG. Analysis of re-replication from deregulated origin licensing by DNA fiber spreading. Nucleic Acids Res 2008; 37:60-9. [PMID: 19010964 PMCID: PMC2615611 DOI: 10.1093/nar/gkn912] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
A major challenge each human cell-division cycle is to ensure that DNA replication origins do not initiate more than once, a phenomenon known as re-replication. Acute deregulation of replication control ultimately causes extensive DNA damage, cell-cycle checkpoint activation and cell death whereas moderate deregulation promotes genome instability and tumorigenesis. In the absence of detectable increases in cellular DNA content however, it has been difficult to directly demonstrate re-replication or to determine if the ability to re-replicate is restricted to a particular cell-cycle phase. Using an adaptation of DNA fiber spreading we report the direct detection of re-replication on single DNA molecules from human chromosomes. Using this method we demonstrate substantial re-replication within 1 h of S phase entry in cells overproducing the replication factor, Cdt1. Moreover, a comparison of the HeLa cancer cell line to untransformed fibroblasts suggests that HeLa cells produce replication signals consistent with low-level re-replication in otherwise unperturbed cell cycles. Re-replication after depletion of the Cdt1 inhibitor, geminin, in an untransformed fibroblast cell line is undetectable by standard assays but readily quantifiable by DNA fiber spreading analysis. Direct evaluation of re-replicated DNA molecules will promote increased understanding of events that promote or perturb genome stability.
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Affiliation(s)
- Elizabeth S Dorn
- Department of Biochemistry and Biophysics, Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7260, USA
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