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Ogawa M, Moriyama M, Midorikawa Y, Nakamura H, Shibata T, Kuroda K, Nakayama H, Kanemaru K, Miki T, Sugitani M, Takayama T. The significance of CDT1 expression in non-cancerous and cancerous liver in cases with hepatocellular carcinoma. J Clin Biochem Nutr 2023; 73:234-248. [PMID: 37970553 PMCID: PMC10636575 DOI: 10.3164/jcbn.23-43] [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: 05/29/2023] [Accepted: 08/01/2023] [Indexed: 11/17/2023] Open
Abstract
We previously reported that chromatin licensing and DNA replication factor 1 (CDT1) expression was associated with the extent of proliferation of atypical hepatocytes and the time to postoperative recurrence in cases of hepatocellular carcinoma (HCC). This study aimed to clarify the clinical significance or pathogenesis of CDT1 expression in both non-cancerous and cancerous liver in HCC cases, including previously published data. We investigated the association between the expression of CDT1 in non-cancerous or cancerous liver tissues and histologic findings or biochemical examination results in 62 cases. We also examined the dual localization between CDT1 and FbxW7, P57kip2, P53 and c-Myc by confocal laser scanning microscopy. CDT1 mRNA expression was significantly higher in cancerous liver than in non-cancerous liver (p<0.0001). Elevated CDT1 mRNA expression indicates a significantly degree of inflammatory cell infiltration within lobules, along with elevated serum transaminase levels, and hepatic spare decline. CDT1 mRNA was highly expressed in a group of poorly differentiated cancer cells. CDT1 co-localized with P57kip2, Fbwx7, P53 and c-Myc in the nucleus or cytoplasm of hepatocytes and cancer cells. We found that CDT1 mRNA expression could represent the degree of hepatic spare ability and the high carcinogenic state.
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Affiliation(s)
- Masahiro Ogawa
- Division of Gastroenterology and Hepatology, Nihon University School of Medicine, 30-1 Oyaguchi-Kamimachi, Itabashi-ku, Tokyo 173-8610, Japan
| | - Mitsuhiko Moriyama
- Division of Gastroenterology and Hepatology, Nihon University School of Medicine, 30-1 Oyaguchi-Kamimachi, Itabashi-ku, Tokyo 173-8610, Japan
- Sashiogi Recuperation Hospital, 1348-1 Hourai, Nishi-ku, Saitama City, Saitama 331-0074, Japan
| | - Yutaka Midorikawa
- Division of Gastroenterology and Hepatology, Nihon University School of Medicine, 30-1 Oyaguchi-Kamimachi, Itabashi-ku, Tokyo 173-8610, Japan
| | - Hitomi Nakamura
- Division of Gastroenterology and Hepatology, Nihon University School of Medicine, 30-1 Oyaguchi-Kamimachi, Itabashi-ku, Tokyo 173-8610, Japan
| | - Toshikatu Shibata
- Division of Gastroenterology and Hepatology, Nihon University School of Medicine, 30-1 Oyaguchi-Kamimachi, Itabashi-ku, Tokyo 173-8610, Japan
| | - Kazumichi Kuroda
- Division of Gastroenterology and Hepatology, Nihon University School of Medicine, 30-1 Oyaguchi-Kamimachi, Itabashi-ku, Tokyo 173-8610, Japan
| | - Hisashi Nakayama
- Department of Digestive Surgery, Department of Medicine, Nihon University School of Medicine, 30-1 Oyaguchi-Kamimachi, Itabashi-ku, Tokyo 173-8610, Japan
| | - Kazunori Kanemaru
- Department of Physiology, Division of Biomedical Sciences, Nihon University School of Medicine, 30-1 Oyaguchi-Kamimachi, Itabashi-ku, Tokyo 173-8610, Japan
| | - Toshio Miki
- Department of Physiology, Division of Biomedical Sciences, Nihon University School of Medicine, 30-1 Oyaguchi-Kamimachi, Itabashi-ku, Tokyo 173-8610, Japan
| | - Masahiko Sugitani
- Department of Pathology, Nihon University School of Medicine, 30-1 Oyaguchi-Kamimachi, Itabashi-ku, Tokyo 173-8610, Japan
| | - Tadatoshi Takayama
- Department of Digestive Surgery, Department of Medicine, Nihon University School of Medicine, 30-1 Oyaguchi-Kamimachi, Itabashi-ku, Tokyo 173-8610, Japan
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2
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The CMG helicase and cancer: a tumor "engine" and weakness with missing mutations. Oncogene 2023; 42:473-490. [PMID: 36522488 PMCID: PMC9948756 DOI: 10.1038/s41388-022-02572-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 12/01/2022] [Accepted: 12/07/2022] [Indexed: 12/23/2022]
Abstract
The replicative Cdc45-MCM-GINS (CMG) helicase is a large protein complex that functions in the DNA melting and unwinding steps as a component of replisomes during DNA replication in mammalian cells. Although the CMG performs this important role in cell growth, the CMG is not a simple bystander in cell cycle events. Components of the CMG, specifically the MCM precursors, are also involved in maintaining genomic stability by regulating DNA replication fork speeds, facilitating recovery from replicative stresses, and preventing consequential DNA damage. Given these important functions, MCM/CMG complexes are highly regulated by growth factors such as TGF-ß1 and by signaling factors such as Myc, Cyclin E, and the retinoblastoma protein. Mismanagement of MCM/CMG complexes when these signaling mediators are deregulated, and in the absence of the tumor suppressor protein p53, leads to increased genomic instability and is a contributor to tumorigenic transformation and tumor heterogeneity. The goal of this review is to provide insight into the mechanisms and dynamics by which the CMG is regulated during its assembly and activation in mammalian genomes, and how errors in CMG regulation due to oncogenic changes promote tumorigenesis. Finally, and most importantly, we highlight the emerging understanding of the CMG helicase as an exploitable vulnerability and novel target for therapeutic intervention in cancer.
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3
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Jaiswal N, Nandi D, Cheema PS, Nag A. The anaphase-promoting complex/cyclosome co-activator, Cdh1, is a novel target of human papillomavirus 16 E7 oncoprotein in cervical oncogenesis. Carcinogenesis 2022; 43:988-1001. [PMID: 35738876 DOI: 10.1093/carcin/bgac057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 06/01/2022] [Accepted: 06/23/2022] [Indexed: 01/13/2023] Open
Abstract
The transforming properties of the high-risk human papillomavirus (HPV) E7 oncoprotein are indispensable for driving the virus life cycle and pathogenesis. Besides inactivation of the retinoblastoma family of tumor suppressors as part of its oncogenic endeavors, E7-mediated perturbations of eminent cell cycle regulators, checkpoint proteins and proto-oncogenes are considered to be the tricks of its transformative traits. However, many such critical interactions are still unknown. In the present study, we have identified the anaphase-promoting complex/cyclosome (APC) co-activator, Cdh1, as a novel interacting partner and a degradation target of E7. We found that HPV16 E7-induced inactivation of Cdh1 promoted abnormal accumulation of multiple Cdh1 substrates. Such a mode of deregulation possibly contributes to HPV-mediated cervical oncogenesis. Our mapping studies recognized the C-terminal zinc-finger motif of E7 to associate with Cdh1 and interfere with the timely degradation of FoxM1, a bona fide Cdh1 substrate and a potent oncogene. Importantly, the E7 mutant with impaired interaction with Cdh1 exhibited defects in its ability for overriding typical cell cycle transition and oncogenic transformation, thereby validating the functional and pathological significance of the E7-Cdh1 axis during cervical carcinoma progression. Altogether, the findings from our study discover a unique nexus between E7 and APC/C-Cdh1, thereby adding to our understanding of the mechanism of E7-induced carcinogenesis and provide a promising target for the management of cervical carcinoma.
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Affiliation(s)
- Neha Jaiswal
- Department of Biochemistry, University of Delhi South Campus, Benito Juarez Marg, New Delhi, India
| | - Deeptashree Nandi
- Department of Biochemistry, University of Delhi South Campus, Benito Juarez Marg, New Delhi, India
| | - Pradeep Singh Cheema
- Department of Biochemistry, University of Delhi South Campus, Benito Juarez Marg, New Delhi, India
| | - Alo Nag
- Department of Biochemistry, University of Delhi South Campus, Benito Juarez Marg, New Delhi, India
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Hendley AM, Rao AA, Leonhardt L, Ashe S, Smith JA, Giacometti S, Peng XL, Jiang H, Berrios DI, Pawlak M, Li LY, Lee J, Collisson EA, Anderson MS, Fragiadakis GK, Yeh JJ, Ye CJ, Kim GE, Weaver VM, Hebrok M. Single-cell transcriptome analysis defines heterogeneity of the murine pancreatic ductal tree. eLife 2021; 10:e67776. [PMID: 34009124 PMCID: PMC8184217 DOI: 10.7554/elife.67776] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 05/18/2021] [Indexed: 12/25/2022] Open
Abstract
To study disease development, an inventory of an organ's cell types and understanding of physiologic function is paramount. Here, we performed single-cell RNA-sequencing to examine heterogeneity of murine pancreatic duct cells, pancreatobiliary cells, and intrapancreatic bile duct cells. We describe an epithelial-mesenchymal transitory axis in our three pancreatic duct subpopulations and identify osteopontin as a regulator of this fate decision as well as human duct cell dedifferentiation. Our results further identify functional heterogeneity within pancreatic duct subpopulations by elucidating a role for geminin in accumulation of DNA damage in the setting of chronic pancreatitis. Our findings implicate diverse functional roles for subpopulations of pancreatic duct cells in maintenance of duct cell identity and disease progression and establish a comprehensive road map of murine pancreatic duct cell, pancreatobiliary cell, and intrapancreatic bile duct cell homeostasis.
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Affiliation(s)
- Audrey M Hendley
- Diabetes Center, University of California, San FranciscoSan FranciscoUnited States
- Center for Bioengineering and Tissue Regeneration, University of California, San FranciscoSan FranciscoUnited States
| | - Arjun A Rao
- CoLabs, University of California, San FranciscoSan FranciscoUnited States
- Bakar ImmunoX Initiative, University of California, San FranciscoSan FranciscoUnited States
| | - Laura Leonhardt
- Diabetes Center, University of California, San FranciscoSan FranciscoUnited States
| | - Sudipta Ashe
- Diabetes Center, University of California, San FranciscoSan FranciscoUnited States
| | - Jennifer A Smith
- Diabetes Center, University of California, San FranciscoSan FranciscoUnited States
| | - Simone Giacometti
- Diabetes Center, University of California, San FranciscoSan FranciscoUnited States
| | - Xianlu L Peng
- Department of Pharmacology, University of North Carolina at Chapel HillChapel HillUnited States
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel HillChapel HillUnited States
| | - Honglin Jiang
- Division of Hematology and Oncology, Department of Medicine and Helen Diller Family Comprehensive Cancer Center, University of California, San FranciscoSan FranciscoUnited States
| | - David I Berrios
- Diabetes Center, University of California, San FranciscoSan FranciscoUnited States
| | - Mathias Pawlak
- Evergrande Center for Immunologic Diseases, Harvard Medical School and Brigham and Women's HospitalBostonUnited States
| | - Lucia Y Li
- Diabetes Center, University of California, San FranciscoSan FranciscoUnited States
| | - Jonghyun Lee
- Diabetes Center, University of California, San FranciscoSan FranciscoUnited States
| | - Eric A Collisson
- Division of Hematology and Oncology, Department of Medicine and Helen Diller Family Comprehensive Cancer Center, University of California, San FranciscoSan FranciscoUnited States
| | - Mark S Anderson
- Diabetes Center, University of California, San FranciscoSan FranciscoUnited States
| | - Gabriela K Fragiadakis
- CoLabs, University of California, San FranciscoSan FranciscoUnited States
- Bakar ImmunoX Initiative, University of California, San FranciscoSan FranciscoUnited States
- Department of Medicine, Division of Rheumatology, University of California, San FranciscoSan FranciscoUnited States
| | - Jen Jen Yeh
- Department of Pharmacology, University of North Carolina at Chapel HillChapel HillUnited States
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel HillChapel HillUnited States
- Department of Surgery, University of North Carolina at Chapel HillChapel HillUnited States
| | - Chun Jimmie Ye
- Parker Institute for Cancer ImmunotherapySan FranciscoUnited States
| | - Grace E Kim
- Department of Pathology, University of California, San FranciscoSan FranciscoUnited States
| | - Valerie M Weaver
- Center for Bioengineering and Tissue Regeneration, University of California, San FranciscoSan FranciscoUnited States
| | - Matthias Hebrok
- Diabetes Center, University of California, San FranciscoSan FranciscoUnited States
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5
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Lewis EMA, Sankar S, Tong C, Patterson ES, Waller LE, Gontarz P, Zhang B, Ornitz DM, Kroll KL. Geminin is required for Hox gene regulation to pattern the developing limb. Dev Biol 2020; 464:11-23. [PMID: 32450229 DOI: 10.1016/j.ydbio.2020.05.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 04/09/2020] [Accepted: 05/13/2020] [Indexed: 02/07/2023]
Abstract
Development of the complex structure of the vertebrate limb requires carefully orchestrated interactions between multiple regulatory pathways and proteins. Among these, precise regulation of 5' Hox transcription factor expression is essential for proper limb bud patterning and elaboration of distinct limb skeletal elements. Here, we identified Geminin (Gmnn) as a novel regulator of this process. A conditional model of Gmnn deficiency resulted in loss or severe reduction of forelimb skeletal elements, while both the forelimb autopod and hindlimb were unaffected. 5' Hox gene expression expanded into more proximal and anterior regions of the embryonic forelimb buds in this Gmnn-deficient model. A second conditional model of Gmnn deficiency instead caused a similar but less severe reduction of hindlimb skeletal elements and hindlimb polydactyly, while not affecting the forelimb. An ectopic posterior SHH signaling center was evident in the anterior hindlimb bud of Gmnn-deficient embryos in this model. This center ectopically expressed Hoxd13, the HOXD13 target Shh, and the SHH target Ptch1, while these mutant hindlimb buds also had reduced levels of the cleaved, repressor form of GLI3, a SHH pathway antagonist. Together, this work delineates a new role for Gmnn in modulating Hox expression to pattern the vertebrate limb.
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Affiliation(s)
- Emily M A Lewis
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Savita Sankar
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Caili Tong
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Ethan S Patterson
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Laura E Waller
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Paul Gontarz
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Bo Zhang
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - David M Ornitz
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Kristen L Kroll
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA.
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6
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Liang SY, Zhou YL, Shu MQ, Lin S. Regulation of geminin by neuropeptide Y in vascular smooth muscle cell proliferation : A current review. Herz 2018; 44:712-716. [PMID: 30151710 DOI: 10.1007/s00059-018-4721-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 05/25/2018] [Accepted: 06/01/2018] [Indexed: 11/30/2022]
Abstract
Geminin, a key regulator of DNA replication licensing in the cell cycle, plays an essential role in determining the fate of cells via suppression of cell proliferation and cellular differentiation. Neuropeptide Y (NPY) intensifies the proliferation of vascular smooth muscle cells (VSMCs) directly by binding with Y1 receptors. In vitro experiments have shown that stimulation of NPY on VSMCs via regulation of geminin is a double-edged sword. Given that the proliferation and the phenotypic transformation of VSMCs increase the risk for progression of atherosclerosis, we focus on the role of geminin interference in determining the fate of VSMCs. Furthermore, we discuss the therapeutic potential of peripheral neurotransmitter interference, thus pointing toward future research directions in the treatment of atherosclerosis.
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Affiliation(s)
- S-Y Liang
- Department of Cardiology, Southwest Hospital, Third Military Medical University, No. 30 Gaotanyan, Shapingba, 400038, Chongqing, China
| | - Y-L Zhou
- Department of Cardiology, Southwest Hospital, Third Military Medical University, No. 30 Gaotanyan, Shapingba, 400038, Chongqing, China
| | - M-Q Shu
- Department of Cardiology, Southwest Hospital, Third Military Medical University, No. 30 Gaotanyan, Shapingba, 400038, Chongqing, China.
| | - S Lin
- Department of Cardiology, Southwest Hospital, Third Military Medical University, No. 30 Gaotanyan, Shapingba, 400038, Chongqing, China.
- School of Health Science, IIIawarra Health and Medical Research Institute, University of Wollongong, NSW 2522, Wollongong City, Australia.
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7
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AAV-Mediated angiotensin 1-7 overexpression inhibits tumor growth of lung cancer in vitro and in vivo. Oncotarget 2018; 8:354-363. [PMID: 27861149 PMCID: PMC5352125 DOI: 10.18632/oncotarget.13396] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 11/11/2016] [Indexed: 11/25/2022] Open
Abstract
Ang-(1-7) inhibits lung cancer cell growth both in vitro and in vivo. However, the molecular mechanism of action is unclear and also the rapid degradation of Ang-(1-7) in vivo limits its clinical application. Here, we have demonstrated that Ang- (1-7) inhibits lung cancer cell growth by interrupting pre-replicative complex assembly and restrains epithelial-mesenchymal transition via Cdc6 inhibition. Furthermore, we constructed a mutant adeno-associated viral vector AAV8 (Y733F) that produced stable and high efficient Ang-(1-7) expression in a xenograft tumor model. The results show that AAV8-mediated Ang-(1-7) over-expression can remarkably suppress tumor growth in vivo by down-regulating Cdc6 and anti-angiogenesis. Ang-(1-7) over-expression via the AAV8 method may be a promising strategy for lung cancer treatment.
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Kushwaha PP, Rapalli KC, Kumar S. Geminin a multi task protein involved in cancer pathophysiology and developmental process: A review. Biochimie 2016; 131:115-127. [PMID: 27702582 DOI: 10.1016/j.biochi.2016.09.022] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 09/29/2016] [Indexed: 02/05/2023]
Abstract
DNA replicates in a timely manner with each cell division. Multiple proteins and factors are involved in the initiation of DNA replication including a dynamic interaction between Cdc10-dependent transcript (Cdt1) and Geminin (GMNN). A conformational change between GMNN-Cdt1 heterotrimer and heterohexamer complex is responsible for licensing or inhibition of the DNA replication. This molecular switch ensures a faithful DNA replication during each S phase of cell cycle. GMNN inhibits Cdt1-mediated minichromosome maintenance helicases (MCM) loading onto the chromatin-bound origin recognition complex (ORC) which results in the inhibition of pre-replication complex assembly. GMNN modulates DNA replication by direct binding to Cdt1, and thereby alters its stability and activity. GMNN is involved in various stages of development such as pre-implantation, germ layer formation, cell commitment and specification, maintenance of genome integrity at mid blastula transition, epithelial to mesenchymal transition during gastrulation, neural development, organogenesis and axis patterning. GMNN interacts with different proteins resulting in enhanced hematopoietic stem cell activity thereby activating the development-associated genes' transcription. GMNN expression is also associated with cancer pathophysiology and development. In this review we discussed the structure and function of GMNN in detail. Inhibitors of GMNN and their role in DNA replication, repair, cell cycle and apoptosis are reviewed. Further, we also discussed the role of GMNN in virus infected host cells.
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Affiliation(s)
- Prem Prakash Kushwaha
- School of Basic and Applied Sciences, Centre for Biochemistry and Microbial Sciences, Central University of Punjab, Bathinda, 151001, India
| | - Krishna Chaitanya Rapalli
- School of Basic and Applied Sciences, Centre for Animal Sciences, Central University of Punjab, Bathinda, 151001, India
| | - Shashank Kumar
- School of Basic and Applied Sciences, Centre for Biochemistry and Microbial Sciences, Central University of Punjab, Bathinda, 151001, India.
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9
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Mukherjee S, Chakraborty P, Saha P. Phosphorylation of Ku70 subunit by cell cycle kinases modulates the replication related function of Ku heterodimer. Nucleic Acids Res 2016; 44:7755-65. [PMID: 27402161 PMCID: PMC5027504 DOI: 10.1093/nar/gkw622] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 06/29/2016] [Accepted: 07/01/2016] [Indexed: 12/18/2022] Open
Abstract
The Ku protein, a heterodimer of Ku70 and Ku80, binds to chromosomal replication origins maximally at G1-phase and plays an essential role in assembly of origin recognition complex. However, the mechanism regulating such a critical periodic activity of Ku remained unknown. Here, we establish human Ku70 as a novel target of cyclin B1-Cdk1, which phosphorylates it in a Cy-motif dependent manner. Interestingly, cyclin E1- and A2-Cdk2 also phosphorylate Ku70, and as a result, the protein remains in a phosphorylated state during S-M phases of cell cycle. Intriguingly, the phosphorylation of Ku70 by cyclin-Cdks abolishes the interaction of Ku protein with replication origin due to disruption of the dimer. Furthermore, Ku70 is dephosphorylated in G1-phase, when Ku interacts with replication origin maximally. Strikingly, the over-expression of Ku70 with non-phosphorylable Cdk targets enhances the episomal replication of Ors8 origin and induces rereplication in HeLa cells, substantiating a preventive role of Ku phosphorylation in premature and untimely licensing of replication origin. Therefore, periodic phosphorylation of Ku70 by cyclin-Cdks prevents the interaction of Ku with replication origin after initiation events in S-phase and the dephosphorylation at the end of mitosis facilitates its participation in pre-replication complex formation.
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Affiliation(s)
- Soumita Mukherjee
- Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, Kolkata 700064, India
| | - Prabal Chakraborty
- Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, Kolkata 700064, India
| | - Partha Saha
- Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, Kolkata 700064, India Homi Bhaba National Institute, Mumbai 400094, India
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10
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USP37 deubiquitinates Cdt1 and contributes to regulate DNA replication. Mol Oncol 2016; 10:1196-206. [PMID: 27296872 DOI: 10.1016/j.molonc.2016.05.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Revised: 05/23/2016] [Accepted: 05/26/2016] [Indexed: 01/25/2023] Open
Abstract
DNA replication control is a key process in maintaining genomic integrity. Monitoring DNA replication initiation is particularly important as it needs to be coordinated with other cellular events and should occur only once per cell cycle. Crucial players in the initiation of DNA replication are the ORC protein complex, marking the origin of replication, and the Cdt1 and Cdc6 proteins, that license these origins to replicate by recruiting the MCM2-7 helicase. To accurately achieve its functions, Cdt1 is tightly regulated. Cdt1 levels are high from metaphase and during G1 and low in S/G2 phases of the cell cycle. This control is achieved, among other processes, by ubiquitination and proteasomal degradation. In an overexpression screen for Cdt1 deubiquitinating enzymes, we isolated USP37, to date the first ubiquitin hydrolase controlling Cdt1. USP37 overexpression stabilizes Cdt1, most likely a phosphorylated form of the protein. In contrast, USP37 knock down destabilizes Cdt1, predominantly during G1 and G1/S phases of the cell cycle. USP37 interacts with Cdt1 and is able to de-ubiquitinate Cdt1 in vivo and, USP37 is able to regulate the loading of MCM complexes onto the chromatin. In addition, downregulation of USP37 reduces DNA replication fork speed. Taken together, here we show that the deubiquitinase USP37 plays an important role in the regulation of DNA replication. Whether this is achieved via Cdt1, a central protein in this process, which we have shown to be stabilized by USP37, or via additional factors, remains to be tested.
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11
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Ohno Y, Suzuki-Takedachi K, Yasunaga S, Kurogi T, Santo M, Masuhiro Y, Hanazawa S, Ohtsubo M, Naka K, Takihara Y. Manipulation of Cell Cycle and Chromatin Configuration by Means of Cell-Penetrating Geminin. PLoS One 2016; 11:e0155558. [PMID: 27195810 PMCID: PMC4873132 DOI: 10.1371/journal.pone.0155558] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 04/29/2016] [Indexed: 02/02/2023] Open
Abstract
Geminin regulates chromatin remodeling and DNA replication licensing which play an important role in regulating cellular proliferation and differentiation. Transcription of the Geminin gene is regulated via an E2F-responsive region, while the protein is being closely regulated by the ubiquitin-proteasome system. Our objective was to directly transduce Geminin protein into cells. Recombinant cell-penetrating Geminin (CP-Geminin) was generated by fusing Geminin with a membrane translocating motif from FGF4 and was efficiently incorporated into NIH 3T3 cells and mouse embryonic fibroblasts. The withdrawal study indicated that incorporated CP-Geminin was quickly reduced after removal from medium. We confirmed CP-Geminin was imported into the nucleus after incorporation and also that the incorporated CP-Geminin directly interacted with Cdt1 or Brahma/Brg1 as the same manner as Geminin. We further demonstrated that incorporated CP-Geminin suppressed S-phase progression of the cell cycle and reduced nuclease accessibility in the chromatin, probably through suppression of chromatin remodeling, indicating that CP-Geminin constitutes a novel tool for controlling chromatin configuration and the cell cycle. Since Geminin has been shown to be involved in regulation of stem cells and cancer cells, CP-Geminin is expected to be useful for elucidating the role of Geminin in stem cells and cancer cells, and for manipulating their activity.
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Affiliation(s)
- Yoshinori Ohno
- Department of Stem Cell Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Kasumi, Minami-ku, Hiroshima, Japan
| | - Kyoko Suzuki-Takedachi
- Department of Stem Cell Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Kasumi, Minami-ku, Hiroshima, Japan
| | - Shin’ichiro Yasunaga
- Department of Stem Cell Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Kasumi, Minami-ku, Hiroshima, Japan
- Department of Biochemistry, Faculty of Medicine, Fukuoka University, Nanakuma, Jonan-ku, Fukuoka, Japan
| | - Toshiaki Kurogi
- Department of Stem Cell Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Kasumi, Minami-ku, Hiroshima, Japan
| | - Mimoko Santo
- Department of Stem Cell Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Kasumi, Minami-ku, Hiroshima, Japan
| | - Yoshikazu Masuhiro
- Department of Applied Biological Sciences, College of Bioresource Sciences, Nihon University, Kameino, Fujisawa-city, Kanagawa, Japan
| | - Shigemasa Hanazawa
- Department of Applied Biological Sciences, College of Bioresource Sciences, Nihon University, Kameino, Fujisawa-city, Kanagawa, Japan
| | - Motoaki Ohtsubo
- Department of Food and Fermentation Science, Faculty of Food Science and Nutrition, Beppu University, Kita-ishigaki 82, Beppu-city, Oita, Japan
| | - Kazuhito Naka
- Department of Stem Cell Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Kasumi, Minami-ku, Hiroshima, Japan
| | - Yoshihiro Takihara
- Department of Stem Cell Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Kasumi, Minami-ku, Hiroshima, Japan
- * E-mail:
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12
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Hyun SY, Jang YJ. p53 activates G₁ checkpoint following DNA damage by doxorubicin during transient mitotic arrest. Oncotarget 2016; 6:4804-15. [PMID: 25605022 PMCID: PMC4467116 DOI: 10.18632/oncotarget.3103] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 12/30/2014] [Indexed: 01/05/2023] Open
Abstract
Recovery from DNA damage is critical for cell survival. The serious damage is not able to be repaired during checkpoint and finally induces cell death to prevent abnormal cell growth. In this study, we demonstrated that 8N-DNA contents are accumulated via re-replication during prolonged recovery period containing serious DNA damage in mitotic cells. During the incubation for recovery, a mitotic delay and initiation of an abnormal interphase without cytokinesis were detected. Whereas a failure of cytokinesis occurred in cells with no relation with p53/p21, re-replication is an anomalous phenomenon in the mitotic DNA damage response in p53/p21 negative cells. Cells with wild-type p53 are accumulated just prior to the initiation of DNA replication through a G1 checkpoint after mitotic DNA damage, even though p53 does not interrupt pre-RC assembly. Finally, these cells undergo cell death by apoptosis. These data suggest that p53 activates G1 checkpoint in response to mitotic DNA damage. Without p53, cells with mitotic DNA damage undergo re-replication leading to accumulation of damage
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Affiliation(s)
- Sun-Yi Hyun
- Department of Nanobiomedical Science & BK21 PLUS Global Research Center for Regenerative Medicine, Dankook University, Cheonan, Korea
| | - Young-Joo Jang
- Department of Nanobiomedical Science & BK21 PLUS Global Research Center for Regenerative Medicine, Dankook University, Cheonan, Korea
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13
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Gadaleta MC, Iwasaki O, Noguchi C, Noma KI, Noguchi E. Chromatin immunoprecipitation to detect DNA replication and repair factors. Methods Mol Biol 2015; 1300:169-86. [PMID: 25916713 DOI: 10.1007/978-1-4939-2596-4_12] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
DNA replication is tightly coupled with DNA repair processes in order to preserve genomic integrity. During DNA replication, the replication fork encounters a variety of obstacles including DNA damage/adducts, secondary structures, and programmed fork-blocking sites, which are all difficult to replicate. The replication fork also collides with the transcription machinery, which shares the template DNA with the replisome complex. Under these conditions, replication forks stall, causing replication stress and/or fork collapse, ultimately leading to genomic instability. The mechanisms to overcome these replication problems remain elusive. Therefore, it is important to investigate how DNA repair and replication factors are recruited and coordinated at chromosomal regions that are difficult to replicate. In this chapter, we describe a chromatin immunoprecipitation method to locate proteins required for DNA repair during DNA replication in the fission yeast Schizosaccharomyces pombe. This method can also easily be adapted to study replisome components or chromatin-associated factors.
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Affiliation(s)
- Mariana C Gadaleta
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, 245 N 15th Street, Philadelphia, PA, 19102, USA
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14
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Leman AR, Noguchi E. The replication fork: understanding the eukaryotic replication machinery and the challenges to genome duplication. Genes (Basel) 2014; 4:1-32. [PMID: 23599899 PMCID: PMC3627427 DOI: 10.3390/genes4010001] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Eukaryotic cells must accurately and efficiently duplicate their genomes during each round of the cell cycle. Multiple linear chromosomes, an abundance of regulatory elements, and chromosome packaging are all challenges that the eukaryotic DNA replication machinery must successfully overcome. The replication machinery, the “replisome” complex, is composed of many specialized proteins with functions in supporting replication by DNA polymerases. Efficient replisome progression relies on tight coordination between the various factors of the replisome. Further, replisome progression must occur on less than ideal templates at various genomic loci. Here, we describe the functions of the major replisome components, as well as some of the obstacles to efficient DNA replication that the replisome confronts. Together, this review summarizes current understanding of the vastly complicated task of replicating eukaryotic DNA.
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Affiliation(s)
- Adam R. Leman
- Authors to whom correspondence should be addressed; E-Mails: (A.R.L.); (E.N.); Tel.: +1-215-762-4825 (E.N.); Fax: +1-215-762-4452 (E.N.)
| | - Eishi Noguchi
- Authors to whom correspondence should be addressed; E-Mails: (A.R.L.); (E.N.); Tel.: +1-215-762-4825 (E.N.); Fax: +1-215-762-4452 (E.N.)
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15
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Garcia K, Blank JL, Bouck DC, Liu XJ, Sappal DS, Hather G, Cosmopoulos K, Thomas MP, Kuranda M, Pickard MD, Liu R, Bandi S, Smith PG, Lightcap ES. Nedd8-activating enzyme inhibitor MLN4924 provides synergy with mitomycin C through interactions with ATR, BRCA1/BRCA2, and chromatin dynamics pathways. Mol Cancer Ther 2014; 13:1625-35. [PMID: 24672057 DOI: 10.1158/1535-7163.mct-13-0634] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
MLN4924 is an investigational small-molecule inhibitor of the Nedd8-activating enzyme currently in phase I clinical trials. MLN4924 induces DNA damage via rereplication in most cell lines. This distinct mechanism of DNA damage may affect its ability to combine with standard-of-care agents and may affect the clinical development of MLN4924. As such, we studied its interaction with other DNA-damaging agents. Mitomycin C, cisplatin, cytarabine, UV radiation, SN-38, and gemcitabine demonstrated synergy in combination with MLN4924 in vitro. The combination of mitomycin C and MLN4924 was shown to be synergistic in a mouse xenograft model. Importantly, depletion of genes within the ataxia telangiectasia and Rad3 related (ATR) and BRCA1/BRCA2 pathways, chromatin modification, and transcription-coupled repair reduced the synergy between mitomycin C and MLN4924. In addition, comet assay demonstrated increased DNA strand breaks with the combination of MLN4924 and mitomycin C. Our data suggest that mitomycin C causes stalled replication forks, which when combined with rereplication induced by MLN4924 results in frequent replication fork collisions, leading to cell death. This study provides a straightforward approach to understand the mechanism of synergy, which may provide useful information for the clinical development of these combinations.
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Affiliation(s)
- Khristofer Garcia
- Authors' Affiliations: Departments of Discovery, Clinical Biostatistics, and Information Technology, Takeda Pharmaceuticals International Co., Cambridge, Massachusetts
| | - Jonathan L Blank
- Authors' Affiliations: Departments of Discovery, Clinical Biostatistics, and Information Technology, Takeda Pharmaceuticals International Co., Cambridge, Massachusetts
| | - David C Bouck
- Authors' Affiliations: Departments of Discovery, Clinical Biostatistics, and Information Technology, Takeda Pharmaceuticals International Co., Cambridge, Massachusetts
| | - Xiaozhen J Liu
- Authors' Affiliations: Departments of Discovery, Clinical Biostatistics, and Information Technology, Takeda Pharmaceuticals International Co., Cambridge, Massachusetts
| | - Darshan S Sappal
- Authors' Affiliations: Departments of Discovery, Clinical Biostatistics, and Information Technology, Takeda Pharmaceuticals International Co., Cambridge, Massachusetts
| | - Greg Hather
- Authors' Affiliations: Departments of Discovery, Clinical Biostatistics, and Information Technology, Takeda Pharmaceuticals International Co., Cambridge, Massachusetts
| | - Katherine Cosmopoulos
- Authors' Affiliations: Departments of Discovery, Clinical Biostatistics, and Information Technology, Takeda Pharmaceuticals International Co., Cambridge, Massachusetts
| | - Michael P Thomas
- Authors' Affiliations: Departments of Discovery, Clinical Biostatistics, and Information Technology, Takeda Pharmaceuticals International Co., Cambridge, Massachusetts
| | - Mike Kuranda
- Authors' Affiliations: Departments of Discovery, Clinical Biostatistics, and Information Technology, Takeda Pharmaceuticals International Co., Cambridge, Massachusetts
| | - Michael D Pickard
- Authors' Affiliations: Departments of Discovery, Clinical Biostatistics, and Information Technology, Takeda Pharmaceuticals International Co., Cambridge, Massachusetts
| | - Ray Liu
- Authors' Affiliations: Departments of Discovery, Clinical Biostatistics, and Information Technology, Takeda Pharmaceuticals International Co., Cambridge, Massachusetts
| | - Syamala Bandi
- Authors' Affiliations: Departments of Discovery, Clinical Biostatistics, and Information Technology, Takeda Pharmaceuticals International Co., Cambridge, Massachusetts
| | - Peter G Smith
- Authors' Affiliations: Departments of Discovery, Clinical Biostatistics, and Information Technology, Takeda Pharmaceuticals International Co., Cambridge, Massachusetts
| | - Eric S Lightcap
- Authors' Affiliations: Departments of Discovery, Clinical Biostatistics, and Information Technology, Takeda Pharmaceuticals International Co., Cambridge, Massachusetts
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16
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Ohno Y, Saeki K, Yasunaga S, Kurogi T, Suzuki-Takedachi K, Shirai M, Mihara K, Yoshida K, Voncken JW, Ohtsubo M, Takihara Y. Transcription of the Geminin gene is regulated by a negative-feedback loop. Mol Biol Cell 2014; 25:1374-83. [PMID: 24554762 PMCID: PMC3983001 DOI: 10.1091/mbc.e13-09-0534] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Geminin transcription, regulated by E2Fs, is negatively regulated by Geminin through the inhibition of chromatin remodeling. Geminin transcription is thus regulated by a negative-feedback loop through the chromatin configuration. Homeostatically regulated Geminin may help couple regulation of DNA replication and transcription. Geminin performs a central function in regulating cellular proliferation and differentiation in development and also in stem cells. Of interest, down-regulation of Geminin induces gene transcription regulated by E2F, indicating that Geminin is involved in regulation of E2F-mediated transcriptional activity. Because transcription of the Geminin gene is reportedly regulated via an E2F-responsive region (E2F-R) located in the first intron, we first used a reporter vector to examine the effect of Geminin on E2F-mediated transcriptional regulation. We found that Geminin transfection suppressed E2F1- and E2F2-mediated transcriptional activation and also mildly suppressed such activity in synergy with E2F5, 6, and 7, suggesting that Geminin constitutes a negative-feedback loop for the Geminin promoter. Of interest, Geminin also suppressed nuclease accessibility, acetylation of histone H3, and trimethylation of histone H3 at lysine 4, which were induced by E2F1 overexpression, and enhanced trimethylation of histone H3 at lysine 27 and monoubiquitination of histone H2A at lysine 119 in E2F-R. However, Geminin5EQ, which does not interact with Brahma or Brg1, did not suppress accessibility to nuclease digestion or transcription but had an overall dominant-negative effect. These findings suggest that E2F-mediated activation of Geminin transcription is negatively regulated by Geminin through the inhibition of chromatin remodeling.
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Affiliation(s)
- Yoshinori Ohno
- Department of Stem Cell Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, 1-2-3, Kasumi, Minami-ku, Hiroshima 734-8553, Japan Department of Hematology and Oncology, Research Institute for Radiation Biology and Medicine, Hiroshima University, 1-2-3, Kasumi, Minami-ku, Hiroshima 734-8553, Japan Department of Bioscience and Genetics, National Cerebral and Cardiovascular Center Research Institute, Suita 562-0025, Japan Department of Life Sciences, Meiji University School of Agriculture, Kawasaki 214-8571, Japan Department of Molecular Genetics, Maastricht University Medical Centre, 6229ER Maastricht, Netherlands Department of Food and Fermentation Science, Faculty of Food Science and Nutrition, Beppu University, Beppu 874-0915, Japan
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17
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Abstract
Cervical cancer, a potentially preventable disease, remains the second most common malignancy in women worldwide. Human papillomavirus is the single most important etiological agent in cervical cancer, contributing to neoplastic progression through the action of viral oncoproteins, mainly E6 and E7, which interfere with critical cell cycle pathways, p53 and retinoblastoma. However, evidence suggests that human papillomavirus infection alone is insufficient to induce malignant changes and that other host genetic variations are important in the development of cervical cancer. This article will discuss the latest molecular profiling techniques available and review the published literature relating to their role in the diagnosis and management of cervical dysplasia and cancer. It is hoped that these techniques will allow the detection of novel biomarkers at DNA, RNA, microRNA and protein levels, which may ultimately play a role in facilitating early disease diagnosis and in predicting response to therapies, thus allowing the development of personalized treatment strategies.
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Affiliation(s)
- Cara M Martin
- Department of Pathology, Coombe Women's Hospital, Dublin 8, Ireland.
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18
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Cell cycle: mechanisms of control and dysregulation in cancer. Mol Oncol 2013. [DOI: 10.1017/cbo9781139046947.039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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19
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Iwahori S, Kohmon D, Kobayashi J, Tani Y, Yugawa T, Komatsu K, Kiyono T, Sugimoto N, Fujita M. ATM regulates Cdt1 stability during the unperturbed S phase to prevent re-replication. Cell Cycle 2013; 13:471-81. [PMID: 24280901 PMCID: PMC3956543 DOI: 10.4161/cc.27274] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Ataxia-telangiectasia mutated (ATM) plays crucial roles in DNA damage responses, especially with regard to DNA double-strand breaks (DSBs). However, it appears that ATM can be activated not only by DSB, but also by some changes in chromatin architecture, suggesting potential ATM function in cell cycle control. Here, we found that ATM is involved in timely degradation of Cdt1, a critical replication licensing factor, during the unperturbed S phase. At least in certain cell types, degradation of p27Kip1 was also impaired by ATM inhibition. The novel ATM function for Cdt1 regulation was dependent on its kinase activity and NBS1. Indeed, we found that ATM is moderately phosphorylated at Ser1981 during the S phase. ATM silencing induced partial reduction in levels of Skp2, a component of SCFSkp2 ubiquitin ligase that controls Cdt1 degradation. Furthermore, Skp2 silencing resulted in Cdt1 stabilization like ATM inhibition. In addition, as reported previously, ATM silencing partially prevented Akt phosphorylation at Ser473, indicative of its activation, and Akt inhibition led to modest stabilization of Cdt1. Therefore, the ATM-Akt-SCFSkp2 pathway may partly contribute to the novel ATM function. Finally, ATM inhibition rendered cells hypersensitive to induction of re-replication, indicating importance for maintenance of genome stability.
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Affiliation(s)
- Satoko Iwahori
- Virology Division; National Cancer Center Research Institute; Chuohku, Tokyo, Japan
| | - Daisuke Kohmon
- Department of Cellular Biochemistry; Graduate School of Pharmaceutical Sciences; Kyushu University; Higashiku, Fukuoka, Japan
| | - Junya Kobayashi
- Radiation Biology Center; Kyoto University; Sakyo-ku, Kyoto, Japan
| | - Yuhei Tani
- Department of Cellular Biochemistry; Graduate School of Pharmaceutical Sciences; Kyushu University; Higashiku, Fukuoka, Japan
| | - Takashi Yugawa
- Virology Division; National Cancer Center Research Institute; Chuohku, Tokyo, Japan
| | - Kenshi Komatsu
- Radiation Biology Center; Kyoto University; Sakyo-ku, Kyoto, Japan
| | - Tohru Kiyono
- Virology Division; National Cancer Center Research Institute; Chuohku, Tokyo, Japan
| | - Nozomi Sugimoto
- Department of Cellular Biochemistry; Graduate School of Pharmaceutical Sciences; Kyushu University; Higashiku, Fukuoka, Japan
| | - Masatoshi Fujita
- Department of Cellular Biochemistry; Graduate School of Pharmaceutical Sciences; Kyushu University; Higashiku, Fukuoka, Japan
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20
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Knockdown of SCF(Skp2) function causes double-parked accumulation in the nucleus and DNA re-replication in Drosophila plasmatocytes. PLoS One 2013; 8:e79019. [PMID: 24205363 PMCID: PMC3812016 DOI: 10.1371/journal.pone.0079019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Accepted: 09/18/2013] [Indexed: 12/25/2022] Open
Abstract
In Drosophila, circulating hemocytes are derived from the cephalic mesoderm during the embryonic wave of hematopoiesis. These cells are contributed to the larva and persist through metamorphosis into the adult. To analyze this population of hemocytes, we considered data from a previously published RNAi screen in the hematopoietic niche, which suggested several members of the SCF complex play a role in lymph gland development. eater-Gal4;UAS-GFP flies were crossed to UAS-RNAi lines to knockdown the function of all known SCF complex members in a plasmatocyte-specific fashion, in order to identify which members are novel regulators of plasmatocytes. This specific SCF complex contains five core members: Lin-19-like, SkpA, Skp2, Roc1a and complex activator Nedd8. The complex was identified by its very distinctive large cell phenotype. Furthermore, these large cells stained for anti-P1, a plasmatocyte-specific antibody. It was also noted that the DNA in these cells appeared to be over-replicated. Gamma-tubulin and DAPI staining suggest the cells are undergoing re-replication as they had multiple centrioles and excessive DNA content. Further experimentation determined enlarged cells were BrdU-positive indicating they have progressed through S-phase. To determine how these cells become enlarged and undergo re-replication, cell cycle proteins were analyzed by immunofluorescence. This analysis identified three proteins that had altered subcellular localization in these enlarged cells: Cyclin E, Geminin and Double-parked. Previous research has shown that Double-parked must be degraded to exit S-phase, otherwise the DNA will undergo re-replication. When Double-parked was titrated from the nucleus by an excess of its inhibitor, geminin, the enlarged cells and aberrant protein localization phenotypes were partially rescued. The data in this report suggests that the SCFSkp2 complex is necessary to ubiquitinate Double-parked during plasmatocyte cell division, ensuring proper cell cycle progression and the generation of a normal population of this essential blood cell type.
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21
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Chen S, Qu X, Wan P, Li QW, Wang Z, Guo F, Bai L, Hu Z, Tan W, Li J. Norcantharidin inhibits pre-replicative complexes assembly of HepG2 cells. THE AMERICAN JOURNAL OF CHINESE MEDICINE 2013; 41:665-82. [PMID: 23711148 DOI: 10.1142/s0192415x13500468] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Norcantharidin (NCTD) is currently used for anticancer therapy but the exact mechanism of action remains unknown. Pre-replicative complexes (pre-RCs) are essential for cell DNA replication and highly related to malignant proliferation. Here, we examined the inhibitory effect of NCTD on pre-RC components in HepG2 cells. We showed that NCTD induced degradation of Cdc6 and Mcm2 in a dose-dependent manner. Under 100 μM NCTD concentration, about 70% of Cdc6 and 50% of Mcm2 were degraded. In addition, the nuclear translocation of Mcm6 was inhibited by NCTD. Further studies aiming at G1 synchronous cells showed that, NCTD reduced the chromatin-bound Cdc6, Mcm2 and Mcm6. Moreover, the cells were blocked from entering the S phase and accumulated at the G1 phase when released synchronously into the cell cycle. Consistently, the DNA replication was inhibited by NCTD. Finally, the combination NCTD with Cdc6 depletion lead to more severe cytotoxicity (88%) than NCTD (52%) and Cdc6 depletion (39%) alone. A synergic cytotoxicity was observed between Cdc6 depletion and NCTD. In conclusion, our results demonstrate that NCTD inhibits pre-RC assembly; subsequently blocks the G1 to S transition; and inhibits DNA replication in HepG2 cells. Pre-RCs are an intriguing target for cancer therapy, which merits further investigations for anticancer development.
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Affiliation(s)
- Sansan Chen
- Institute of Biotherapy, School of Biotechnology, Southern Medical University, Guangzhou, China
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22
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Dimaki M, Xouri G, Symeonidou IE, Sirinian C, Nishitani H, Taraviras S, Lygerou Z. Cell cycle-dependent subcellular translocation of the human DNA licensing inhibitor geminin. J Biol Chem 2013; 288:23953-63. [PMID: 23814078 DOI: 10.1074/jbc.m113.453092] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Once per cell cycle replication is crucial for maintaining genome integrity. Geminin interacts with the licensing factor Cdt1 to prevent untimely replication and is controlled by APC/C-dependent cell cycle specific proteolysis during mitosis and in G1. We show here that human geminin, when expressed in human cells in culture under a constitutive promoter, is excluded from the nucleus during part of the G1 phase and at the transition from G0 to G1. The N-terminal 30 amino acids of geminin, which contain its destruction box, are essential for nuclear exclusion. In addition, 30 amino acids within the central domain of geminin are required for both nuclear exclusion and nuclear accumulation. Cdt1 overexpression targets geminin to the nucleus, while reducing Cdt1 levels by RNAi leads to the appearance of endogenous geminin in the cytoplasm. Our data propose a novel means of regulating the balance of Cdt1/geminin in human cells, at the level of the subcellular localization of geminin.
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Affiliation(s)
- Maria Dimaki
- Laboratory of General Biology, School of Medicine, University of Patras, 26500 Rio, Patras, Greece
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23
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CHEN SANSAN, WAN PEI, DING WEN, LI FEI, HE CHENGWU, CHEN PENGLIANG, LI HONGWEI, HU ZHIMING, TAN WANLONG, LI JINLONG. Norcantharidin inhibits DNA replication and induces mitotic catastrophe by degrading initiation protein Cdc6. Int J Mol Med 2013; 32:43-50. [DOI: 10.3892/ijmm.2013.1359] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Accepted: 04/08/2013] [Indexed: 11/06/2022] Open
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24
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Shen L, Nishioka T, Guo J, Chen C. Geminin functions downstream of p53 in K-ras-induced gene amplification of dihydrofolate reductase. Cancer Res 2012; 72:6153-62. [PMID: 23026135 DOI: 10.1158/0008-5472.can-12-1862] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
DNA strand breakage and perturbation of cell-cycle progression contribute to gene amplification events that can drive cancer. In cells lacking p53, DNA damage does not trigger an effective cell-cycle arrest and in this setting promotes gene amplification. This is also increased in cells harboring oncogenic Ras, in which cell-cycle arrest is perturbed and ROS levels that cause DNA single strand breaks are elevated. This study focused on the effects of v-K-ras and p53 on Methotrexate (MTX)-mediated DHFR amplification. Rat lung epithelial cells expressing v-K-ras or murine lung cancer LKR cells harboring active K-ras continued cell-cycle progression when treated with MTX. However, upon loss of p53, amplification of DHFR and formation of MTX-resistant colonies occurred. Expression levels of cyclin A, Geminin, and Cdt1 were increased in v-K-ras transfectants. Geminin was sufficient to prevent the occurrence of multiple replications via interaction with Cdt1 after MTX treatment, and DHFR amplification proceeded in v-K-ras transfectants that possess a functional p53 in the absence of geminin. Taken together, our findings indicate that p53 not only regulates cell-cycle progression, but also functions through geminin to prevent DHFR amplification and protect genomic integrity.
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Affiliation(s)
- Ling Shen
- Department of Radiation Oncology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
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25
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Depamphilis ML, de Renty CM, Ullah Z, Lee CY. "The Octet": Eight Protein Kinases that Control Mammalian DNA Replication. Front Physiol 2012; 3:368. [PMID: 23055977 PMCID: PMC3458233 DOI: 10.3389/fphys.2012.00368] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2012] [Accepted: 08/27/2012] [Indexed: 01/12/2023] Open
Abstract
Development of a fertilized human egg into an average sized adult requires about 29 trillion cell divisions, thereby producing enough DNA to stretch to the Sun and back 200 times (DePamphilis and Bell, 2011)! Even more amazing is the fact that throughout these mitotic cell cycles, the human genome is duplicated once and only once each time a cell divides. If a cell accidentally begins to re-replicate its nuclear DNA prior to cell division, checkpoint pathways trigger apoptosis. And yet, some cells are developmentally programmed to respond to environmental cues by switching from mitotic cell cycles to endocycles, a process in which multiple S phases occur in the absence of either mitosis or cytokinesis. Endocycles allow production of viable, differentiated, polyploid cells that no longer proliferate. What is surprising is that among the 516 (Manning et al., 2002) to 557 (BioMart web site) protein kinases encoded by the human genome, only eight regulate nuclear DNA replication directly. These are Cdk1, Cdk2, Cdk4, Cdk6, Cdk7, Cdc7, Checkpoint kinase-1 (Chk1), and Checkpoint kinase-2. Even more remarkable is the fact that only four of these enzymes (Cdk1, Cdk7, Cdc7, and Chk1) are essential for mammalian development. Here we describe how these protein kinases determine when DNA replication occurs during mitotic cell cycles, how mammalian cells switch from mitotic cell cycles to endocycles, and how cancer cells can be selectively targeted for destruction by inducing them to begin a second S phase before mitosis is complete.
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Affiliation(s)
- Melvin L Depamphilis
- Program in Genomics of Differentiation, National Institute of Child Health and Human Development, National Institutes of Health Bethesda, MD, USA
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26
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Suzuki M, Takahashi T. Aberrant DNA replication in cancer. Mutat Res 2012; 743-744:111-117. [PMID: 22968031 DOI: 10.1016/j.mrfmmm.2012.07.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Revised: 07/26/2012] [Accepted: 07/31/2012] [Indexed: 12/11/2022]
Abstract
Genomic instability plays an important role in cancer susceptibility, though the mechanics of its development remain unclear. An often-stated hypothesis is that error-prone phenotypes in DNA replication or aberrations in translesion DNA synthesis lead to genomic instability and cancer. Mutations in core DNA replication proteins have been identified in human cancer, although DNA replication is essential for cell proliferation and most mutations eliminating this function are deleterious. With recent developments in this field we review and discuss the possible involvement of DNA replication proteins in carcinogenesis.
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Affiliation(s)
- Motoshi Suzuki
- Division of Molecular Carcinogenesis, Nagoya University Graduate School of Medicine, Nagoya, Japan.
| | - Takashi Takahashi
- Division of Molecular Carcinogenesis, Nagoya University Graduate School of Medicine, Nagoya, Japan
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27
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Dynamic association of ORCA with prereplicative complex components regulates DNA replication initiation. Mol Cell Biol 2012; 32:3107-20. [PMID: 22645314 DOI: 10.1128/mcb.00362-12] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
In eukaryotes, initiation of DNA replication requires the assembly of a multiprotein prereplicative complex (pre-RC) at the origins. We recently reported that a WD repeat-containing protein, origin recognition complex (ORC)-associated (ORCA/LRWD1), plays a crucial role in stabilizing ORC to chromatin. Here, we find that ORCA is required for the G(1)-to-S-phase transition in human cells. In addition to binding to ORC, ORCA associates with Cdt1 and its inhibitor, geminin. Single-molecule pulldown experiments demonstrate that each molecule of ORCA can bind to one molecule of ORC, one molecule of Cdt1, and two molecules of geminin. Further, ORCA directly interacts with the N terminus of Orc2, and the stability of ORCA is dependent on its association with Orc2. ORCA associates with Orc2 throughout the cell cycle, with Cdt1 during mitosis and G(1), and with geminin in post-G(1) cells. Overexpression of geminin results in the loss of interaction between ORCA and Cdt1, suggesting that increased levels of geminin in post-G(1) cells titrate Cdt1 away from ORCA. We propose that the dynamic association of ORCA with pre-RC components modulates the assembly of its interacting partners on chromatin and facilitates DNA replication initiation.
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Regulation of cell cycle progression by forkhead transcription factor FOXO3 through its binding partner DNA replication factor Cdt1. Proc Natl Acad Sci U S A 2012; 109:5717-22. [PMID: 22451935 DOI: 10.1073/pnas.1203210109] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To ensure genome stability, DNA must be replicated once and only once during each cell cycle. Cdt1 is tightly regulated to make sure that cells do not rereplicate their DNA. Multiple regulatory mechanisms operate to ensure degradation of Cdt1 in S phase. However, little is known about the positive regulators of Cdt1 under physiological conditions. Here we identify FOXO3 as a binding partner of Cdt1. FOXO3 forms a protein complex with Cdt1, which in turn blocks its interaction with DDB1 and PCNA. Conversely, FOXO3 depletion facilitated the proteolysis of Cdt1 in unperturbed cells. Intriguingly, FOXO3 deficiency resulted in impaired S-phase entry and reduced cell proliferation. We provide data that FOXO3 knockdown mimics Cdt1 down-regulation and affects G1/S transitions. Our results demonstrate a unique role of FOXO3 in binding to Cdt1 and maintaining its level required for cell cycle progression.
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Sacco E, Hasan MM, Alberghina L, Vanoni M. Comparative analysis of the molecular mechanisms controlling the initiation of chromosomal DNA replication in yeast and in mammalian cells. Biotechnol Adv 2012; 30:73-98. [DOI: 10.1016/j.biotechadv.2011.09.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Accepted: 09/14/2011] [Indexed: 11/26/2022]
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30
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Histology of cervical intraepithelial neoplasia and the role of biomarkers. Best Pract Res Clin Obstet Gynaecol 2011; 25:605-15. [DOI: 10.1016/j.bpobgyn.2011.04.005] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Revised: 03/31/2011] [Accepted: 04/23/2011] [Indexed: 11/19/2022]
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Gardner L, Malik R, Shimizu Y, Mullins N, ElShamy WM. Geminin overexpression prevents the completion of topoisomerase IIα chromosome decatenation, leading to aneuploidy in human mammary epithelial cells. Breast Cancer Res 2011; 13:R53. [PMID: 21595939 PMCID: PMC3218940 DOI: 10.1186/bcr2884] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 04/16/2011] [Accepted: 05/19/2011] [Indexed: 11/10/2022] Open
Abstract
INTRODUCTION The nuclear enzyme topoisomerase IIα (TopoIIα) is able to cleave DNA in a reversible manner, making it a valuable target for agents such as etoposide that trap the enzyme in a covalent bond with the 5' DNA end to which it cleaves. This prevents DNA religation and triggers cell death in cancer cells. However, development of resistance to these agents limits their therapeutic use. In this study, we examined the therapeutic targeting of geminin for improving the therapeutic potential of TopoIIα agents. METHODS Human mammary epithelial (HME) cells and several breast cancer cell lines were used in this study. Geminin, TopoIIα and cell division cycle 7 (Cdc7) silencing were done using specific small interfering RNA. Transit or stable inducible overexpression of these proteins and casein kinase Iε (CKIε) were also used, as well as several pharmacological inhibitors that target TopoIIα, Cdc7 or CKIε. We manipulated HME cells that expressed H2B-GFP, or did not, to detect chromosome bridges. Immunoprecipitation and direct Western blot analysis were used to detect interactions between these proteins and their total expression, respectively, whereas interactions on chromosomal arms were detected using a trapped in agarose DNA immunostaining assay. TopoIIα phosphorylation by Cdc7 or CKIε was done using an in vitro kinase assay. The TopoGen decatenation kit was used to measure TopoIIα decatenation activity. Finally, a comet assay and metaphase chromosome spread were used to detect chromosome breakage and changes in chromosome condensation or numbers, respectively. RESULTS We found that geminin and TopoIIα interact primarily in G2/M/early G1 cells on chromosomes, that geminin recruits TopoIIα to chromosomal decatenation sites or vice versa and that geminin silencing in HME cells triggers the formation of chromosome bridges by suppressing TopoIIα access to chromosomal arms. CKIε kinase phosphorylates and positively regulates TopoIIα chromosome localization and function. CKIε kinase overexpression or Cdc7 kinase silencing, which we show phosphorylates TopoIIα in vitro, restored DNA decatenation and chromosome segregation in geminin-silenced cells before triggering cell death. In vivo, at normal concentration, geminin recruits the deSUMOylating sentrin-specific proteases SENP1 and SENP2 enzymes to deSUMOylate chromosome-bound TopoIIα and promote its release from chromosomes following completion of DNA decatenation. In cells overexpressing geminin, premature departure of TopoIIα from chromosomes is thought to be due to the fact that geminin recruits more of these deSUMOylating enzymes, or recruits them earlier, to bound TopoIIα. This triggers premature release of TopoIIα from chromosomes, which we propose induces aneuploidy in HME cells, since chromosome breakage generated through this mechanism were not sensed and/or repaired and the cell cycle was not arrested. Expression of mitosis-inducing proteins such as cyclin A and cell division kinase 1 was also increased in these cells because of the overexpression of geminin. CONCLUSIONS TopoIIα recruitment and its chromosome decatenation function require a normal level of geminin. Geminin silencing induces a cytokinetic checkpoint in which Cdc7 phosphorylates TopoIIα and inhibits its chromosomal recruitment and decatenation and/or segregation function. Geminin overexpression prematurely deSUMOylates TopoIIα, triggering its premature departure from chromosomes and leading to chromosomal abnormalities and the formation of aneuploid, drug-resistant cancer cells. On the basis of our findings, we propose that therapeutic targeting of geminin is essential for improving the therapeutic potential of TopoIIα agents.
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Affiliation(s)
- Lauren Gardner
- Cancer Institute, Department of Biochemistry, University of Mississippi Medical Center, Jackson, 39216, USA
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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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Id1 enhances RING1b E3 ubiquitin ligase activity through the Mel-18/Bmi-1 polycomb group complex. Oncogene 2010; 29:5818-27. [PMID: 20697353 DOI: 10.1038/onc.2010.317] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The helix-loop-helix inhibitor of differentiation and DNA binding (Id1) is well known as an oncogene in various tumors. Although it has been reported that Id1 promotes several oncogenic processes, it is still unclear whether Id1 functions through epigenetic transcriptional regulation. In this study, we examined the effect of Id1 on polycomb group (PcG) proteins, which are crucial epigenetic gene silencers, and found that Id1 regulated the expression of Mel-18 and Bmi-1, both of which belong to polycomb repressive complex 1. We also confirmed that Id1 induced Mel-18 downregulation, which was mediated by the Akt pathway, and consequently upregulated the transcription of its target gene, c-Myc. Using a promoter-reporter, we demonstrated that Id1 regulated Bmi-1 transcription through c-Myc binding to its E-box in the promoter. Finally, we examined the activity of E3 ligase RING1b, whose catalytic activity is increased by binding with the RING finger protein Bmi-1, and found that Id1 overexpression enhanced RING1b E3 ligase activity leading to accumulation of H2A ubiquitination and ubiquitin/proteasome-mediated degradation of geminin. Taken together, our study provided a novel link between Id1 and PcG proteins and suggested that Id1 may contribute to tumor development through PcG-mediated epigenetic regulation.
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Masai H, Matsumoto S, You Z, Yoshizawa-Sugata N, Oda M. Eukaryotic chromosome DNA replication: where, when, and how? Annu Rev Biochem 2010; 79:89-130. [PMID: 20373915 DOI: 10.1146/annurev.biochem.052308.103205] [Citation(s) in RCA: 370] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
DNA replication is central to cell proliferation. Studies in the past six decades since the proposal of a semiconservative mode of DNA replication have confirmed the high degree of conservation of the basic machinery of DNA replication from prokaryotes to eukaryotes. However, the need for replication of a substantially longer segment of DNA in coordination with various internal and external signals in eukaryotic cells has led to more complex and versatile regulatory strategies. The replication program in higher eukaryotes is under a dynamic and plastic regulation within a single cell, or within the cell population, or during development. We review here various regulatory mechanisms that control the replication program in eukaryotes and discuss future directions in this dynamic field.
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Affiliation(s)
- Hisao Masai
- Genome Dynamics Project, Tokyo Metropolitan Institute of Medical Science, Tokyo 156-8506, Japan.
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Miotto B, Struhl K. HBO1 histone acetylase activity is essential for DNA replication licensing and inhibited by Geminin. Mol Cell 2010; 37:57-66. [PMID: 20129055 DOI: 10.1016/j.molcel.2009.12.012] [Citation(s) in RCA: 184] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2009] [Revised: 09/16/2009] [Accepted: 11/16/2009] [Indexed: 12/15/2022]
Abstract
HBO1, an H4-specific histone acetylase, is a coactivator of the DNA replication licensing factor Cdt1. HBO1 acetylase activity is required for licensing, because a histone acetylase (HAT)-defective mutant of HBO1 bound at origins is unable to load the MCM complex. H4 acetylation at origins is cell-cycle regulated, with maximal activity at the G1/S transition, and coexpression of HBO1 and Jade-1 increases histone acetylation and MCM complex loading. Overexpression of the Set8 histone H4 tail-binding domain specifically inhibits MCM loading, suggesting that histones are a physiologically relevant target for licensing. Lastly, Geminin inhibits HBO1 acetylase activity in the context of a Cdt1-HBO1 complex, and it associates with origins and inhibits H4 acetylation and licensing in vivo. Thus, H4 acetylation at origins by HBO1 is critical for replication licensing by Cdt1, and negative regulation of licensing by Geminin is likely to involve inhibition of HBO1 histone acetylase activity.
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Affiliation(s)
- Benoit Miotto
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
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36
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Paulsen RD, Soni DV, Wollman R, Hahn AT, Yee MC, Guan A, Hesley JA, Miller SC, Cromwell EF, Solow-Cordero DE, Meyer T, Cimprich KA. A genome-wide siRNA screen reveals diverse cellular processes and pathways that mediate genome stability. Mol Cell 2009; 35:228-39. [PMID: 19647519 DOI: 10.1016/j.molcel.2009.06.021] [Citation(s) in RCA: 421] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2009] [Revised: 05/21/2009] [Accepted: 06/26/2009] [Indexed: 12/26/2022]
Abstract
Signaling pathways that respond to DNA damage are essential for the maintenance of genome stability and are linked to many diseases, including cancer. Here, a genome-wide siRNA screen was employed to identify additional genes involved in genome stabilization by monitoring phosphorylation of the histone variant H2AX, an early mark of DNA damage. We identified hundreds of genes whose downregulation led to elevated levels of H2AX phosphorylation (gammaH2AX) and revealed links to cellular complexes and to genes with unclassified functions. We demonstrate a widespread role for mRNA-processing factors in preventing DNA damage, which in some cases is caused by aberrant RNA-DNA structures. Furthermore, we connect increased gammaH2AX levels to the neurological disorder Charcot-Marie-Tooth (CMT) syndrome, and we find a role for several CMT proteins in the DNA-damage response. These data indicate that preservation of genome stability is mediated by a larger network of biological processes than previously appreciated.
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Affiliation(s)
- Renee D Paulsen
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA 94305, USA
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37
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Narasimhachar Y, Coué M. Geminin stabilizes Cdt1 during meiosis in Xenopus oocytes. J Biol Chem 2009; 284:27235-42. [PMID: 19656945 DOI: 10.1074/jbc.m109.008854] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
During the mitotic cell cycle, Geminin can act both as a promoter and inhibitor of initiation of DNA replication. As a promoter, Geminin stabilizes Cdt1 and facilitates its accumulation leading to the assembly of the pre-replication complex on DNA. As an inhibitor, Geminin prevents Cdt1 from loading the mini-chromosome maintenance complex onto pre-replication complexes in late S, G(2), and M phases. Here we show that during meiosis Geminin functions as a stabilizer of Cdt1 promoting its accumulation for the early division cycles of the embryo. Depletion of Geminin in Xenopus immature oocytes leads to a decrease of Cdt1 protein levels during maturation and after activation of these oocytes. Injection of exogenous recombinant Geminin into the depleted oocytes rescues Cdt1 levels demonstrating that Geminin stabilizes Cdt1 during meiosis and after fertilization. Furthermore, Geminin-depleted oocytes did not replicate their DNA after meiosis I indicating that Geminin does not act as an inhibitor of initiation of DNA replication between meiosis I and meiosis II.
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Affiliation(s)
- Yadushyla Narasimhachar
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA.
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38
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Abstract
Eukaryotic cells normally restrict genome duplication to once per cell division. In metazoa, re-replication of DNA during a single S phase seems to be prevented solely by suppressing CDT1 activity, a protein required for loading the replicative MCM DNA helicase. However, siRNA suppression of geminin (a specific inhibitor of CDT1) arrested proliferation only of cells derived from cancers by inducing DNA re-replication and DNA damage that spontaneously triggered apoptosis. None of these effects were detected either in cells derived from normal human tissues or in cells immortalized by a viral oncogene. To induce these effects in noncancer cells required suppression of both geminin and cyclin A, another cell cycle regulator. Therefore, initiating DNA replication in some cancer cells is limited solely by regulating the level of CDT1 activity with geminin, whereas noncancer cells contain additional safeguards that prevent DNA re-replication. These results show that inhibition of geminin activity could be used to selectively kill cancer cells without harming other cells.
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Affiliation(s)
- Wenge Zhu
- National Institute of Child Health and Human Development, NIH, Bethesda, Maryland 20892-2753, USA
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Lin HC, Wu JT, Tan BCM, Chien CT. Cul4 and DDB1 regulate Orc2 localization, BrdU incorporation and Dup stability during gene amplification in Drosophila follicle cells. J Cell Sci 2009; 122:2393-401. [PMID: 19531585 DOI: 10.1242/jcs.042861] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
In higher eukaryotes, the pre-replication complex (pre-RC) component Cdt1 is the major regulator in licensing control for DNA replication. The Cul4-DDB1-based ubiquitin ligase mediates Cdt1 ubiquitylation for subsequent proteolysis. During the initiation of chorion gene amplification, Double-parked (Dup), the Drosophila ortholog of Cdt1, is restricted to chorion gene foci. We found that Dup accumulated in nuclei in Cul4 mutant follicle cells, and the accumulation was less prominent in DDB1 mutant cells. Loss of Cul4 or DDB1 activity in follicle cells also compromised chorion gene amplification and induced ectopic genomic DNA replication. The focal localization of Orc2, a subunit of the origin recognition complex, is frequently absent in Cul4 mutant follicle cells. Therefore, Cul4 and DDB1 have differential functions during chorion gene amplification.
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Affiliation(s)
- Hsiu-Chen Lin
- Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan
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40
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Ullah Z, Lee CY, Depamphilis ML. Cip/Kip cyclin-dependent protein kinase inhibitors and the road to polyploidy. Cell Div 2009; 4:10. [PMID: 19490616 PMCID: PMC2697143 DOI: 10.1186/1747-1028-4-10] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Accepted: 06/02/2009] [Indexed: 02/07/2023] Open
Abstract
Cyclin-dependent kinases (CDKs) play a central role in the orderly transition from one phase of the eukaryotic mitotic cell division cycle to the next. In this context, p27Kip1 (one of the CIP/KIP family of CDK specific inhibitors in mammals) or its functional analogue in other eukarya prevents a premature transition from G1 to S-phase. Recent studies have revealed that expression of a second member of this family, p57Kip2, is induced as trophoblast stem (TS) cells differentiate into trophoblast giant (TG) cells. p57 then inhibits CDK1 activity, an enzyme essential for initiating mitosis, thereby triggering genome endoreduplication (multiple S-phases without an intervening mitosis). Expression of p21Cip1, the third member of this family, is also induced in during differentiation of TS cells into TG cells where it appears to play a role in suppressing the DNA damage response pathway. Given the fact that p21 and p57 are unique to mammals, the question arises as to whether one or both of these proteins are responsible for the induction and maintenance of polyploidy during mammalian development.
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Affiliation(s)
- Zakir Ullah
- National Institute of Child Health and Human Development, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892-2753, USA.
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41
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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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42
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Ullah Z, Lee CY, Lilly MA, DePamphilis ML. Developmentally programmed endoreduplication in animals. Cell Cycle 2009; 8:1501-9. [PMID: 19372757 DOI: 10.4161/cc.8.10.8325] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Development of a fertilized egg into an adult human requires trillions of cell divisions, the vast majority of which duplicate their genome once and only once. Nevertheless, trophoblast giant cells and megakaryocytes in mammals circumvent this rule by duplicating their genome multiple times without undergoing cell division, a process generally referred to as 'endoreduplication'. In contrast, arthropods such as Drosophila endoreduplicate their genome in most larval tissues, as well as in many adult tissues. Endoreduplication requires that cells prevent entrance into or completion of mitosis and cytokinesis under conditions that permit assembly of prereplication complexes. In addition, cells must prevent induction of apoptosis in response to incomplete DNA replication or DNA damage that may occur during the ensuing sequence of 'endocycles'. Thus, developmentally regulated endoreduplication results in terminal cell differentiation. Recent progress has revealed both differences and similarities in the mechanisms employed by flies and mammals to change from mitotic cell cycles to 'endocycles'. The critical step, however, appears to be switching from a CDK-dependent form of the anaphase promoting complex (APC) to one that functions only in the absence of CDK activity.
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Affiliation(s)
- Zakir Ullah
- Genomics of Differentiation Program, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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Liu X, Huang S, Ma J, Li C, Zhang Y, Luo L. NF-kappaB and Snail1a coordinate the cell cycle with gastrulation. ACTA ACUST UNITED AC 2009; 184:805-15. [PMID: 19307597 PMCID: PMC2699144 DOI: 10.1083/jcb.200806074] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The cell cycle needs to strictly coordinate with developmental processes to ensure correct generation of the body plan and different tissues. However, the molecular mechanism underlying the coordination remains largely unknown. In this study, we investigate how the cell cycle coordinates gastrulation cell movements in zebrafish. We present a system to modulate the cell cycle in early zebrafish embryos by manipulating the geminin-Cdt1 balance. Alterations of the cell cycle change the apoptotic level during gastrulation, which correlates with the nuclear level of antiapoptotic nuclear factor κB (NF-κB). NF-κB associates with the Snail1a promoter region on the chromatin and directly activates Snail1a, an important factor controlling cell delamination, which is the initial step of mesendodermal cell movements during gastrulation. In effect, the cell cycle coordinates the delamination of mesendodermal cells through the transcription of Snail1a. Our results suggest a molecular mechanism by which NF-κB and Snail1a coordinate the cell cycle through gastrulation.
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Affiliation(s)
- Xiaolin Liu
- Key Laboratory of Aquatic Organism Reproduction and Development, Ministry of Education, Key Laboratory of Aquatic Science of Chongqing, School of Life Science, Southwest University, Beibei, Chongqing, China
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Miotto B, Struhl K. HBO1 histone acetylase is a coactivator of the replication licensing factor Cdt1. Genes Dev 2008; 22:2633-8. [PMID: 18832067 DOI: 10.1101/gad.1674108] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
HBO1 histone acetylase is important for DNA replication licensing. In human cells, HBO1 associates with replication origins specifically during the G1 phase of the cell cycle in a manner that depends on the replication licensing factor Cdt1, but is independent of the Cdt1 repressor Geminin. HBO1 directly interacts with Cdt1, and it enhances Cdt1-dependent rereplication. Thus, HBO1 plays a direct role at replication origins as a coactivator of the Cdt1 licensing factor. As HBO1 is also a transcriptional coactivator, it has the potential to integrate internal and external stimuli to coordinate transcriptional responses with initiation of DNA replication.
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Affiliation(s)
- Benoit Miotto
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
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45
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Rakotomalala L, Studach L, Wang WH, Gregori G, Hullinger RL, Andrisani O. Hepatitis B virus X protein increases the Cdt1-to-geminin ratio inducing DNA re-replication and polyploidy. J Biol Chem 2008; 283:28729-40. [PMID: 18693245 PMCID: PMC2568909 DOI: 10.1074/jbc.m802751200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Revised: 07/24/2008] [Indexed: 12/16/2022] Open
Abstract
Hepatitis B virus X protein (pX) is implicated in hepatocellular carcinoma pathogenesis by an unknown mechanism. Employing the tetracycline-regulated pX-expressing 4pX-1 cell line, derived from the murine AML12 hepatocyte cell line, we demonstrate that pX induces partial polyploidy (>4N DNA). Depletion of p53 in 4pX-1 cells increases by 5-fold the polyploid cells in response to pX expression, indicating that p53 antagonizes pX-induced polyploidy. Dual-parameter flow cytometric analyses show pX-dependent bromodeoxyuridine (BrdUrd) incorporation in 4pX-1 cells containing 4N and >4N DNA, suggesting pX induces DNA re-replication. Interestingly, pX increases expression of endogenous replication initiation factors Cdc6 and Cdtl while suppressing geminin expression, a negative regulator of rereplication. In comparison to a geminin knockdown 4pX-1 cell line used as DNA re-replication control, the Cdt1/geminin ratio is greater in 4pX-1 cells expressing pX, indicating that pX promotes DNA re-replication. In support of this conclusion, pX-expressing 4pX-1 cells, similar to the geminin knockdown 4pX-1 cells, continue to incorporate BrdUrd in the G2 phase and exhibit nuclear Cdc6 and MCM5 co-localization and the absence of geminin. In addition, pX expression activates the ATR kinase, the sensor of DNA re-replication, which in turn phosphorylates RAD17 and H2AX. Interestingly, phospho-H2AX-positive and BrdUrd -positive cells progress through mitosis, demonstrating a link between pX-induced DNA re-replication and polyploidy. Our studies high-light a novel function of pX that likely contributes to hepatocellular carcinoma pathogenesis.
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Affiliation(s)
- Lova Rakotomalala
- Department of Basic Medical Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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Polycomb-group complex 1 acts as an E3 ubiquitin ligase for Geminin to sustain hematopoietic stem cell activity. Proc Natl Acad Sci U S A 2008; 105:10396-401. [PMID: 18650381 DOI: 10.1073/pnas.0800672105] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Polycomb-group (PcG) genes encode multimeric nuclear protein complexes, PcG complex 1 and 2. PcG complex 2 was proved to induce transcription repression and to further methylate histone H3 at lysine-27 (H3K27). Subsequently PcG complex 1 is recruited through recognition of methylated H3K27 and maintains the transcription silencing by mediating monoubiquitination of histone H2A at lysine-119. Genetic evidence demonstrated a crucial role for PcG complex 1 in stem cells, and Bmi1, a member of PcG complex 1, was shown to sustain adult stem cells through direct repression of the INK4a locus encoding cyclin-dependent kinase inhibitor, p16CKI, and p19ARF. The molecular functions of PcG complex 1, however, remain insufficiently understood. In our study, deficiency of Rae28, a member of PcG complex 1, was found to impair ubiquitin-proteasome-mediated degradation of Geminin, an inhibitor of DNA replication licensing factor Cdt1, and to increase protein stability. The resultant accumulation of Geminin, based on evidence from retroviral transduction experiments, presumably eliminated hematopoietic stem cell activity in Rae28-deficient mice. Rae28 mediates recruiting Scmh1, which provides PcG complex 1 an interaction domain for Geminin. Moreover, PcG complex 1 acts as the E3 ubiquitin ligase for Geminin, as we demonstrated in vivo as well as in vitro by using purified recombinant PcG complex 1 reconstituted in insect cells. Our findings suggest that PcG complex 1 supports the activity of hematopoietic stem cells, in which high-level Geminin expression induces quiescence securing genome stability, by enhancing cycling capability and hematopoietic activity through direct regulation of Geminin.
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Hall JR, Lee HO, Bunker BD, Dorn ES, Rogers GC, Duronio RJ, Cook JG. Cdt1 and Cdc6 are destabilized by rereplication-induced DNA damage. J Biol Chem 2008; 283:25356-25363. [PMID: 18617514 DOI: 10.1074/jbc.m802667200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The replication factors Cdt1 and Cdc6 are essential for origin licensing, a prerequisite for DNA replication initiation. Mechanisms to ensure that metazoan origins initiate once per cell cycle include degradation of Cdt1 during S phase and inhibition of Cdt1 by the geminin protein. Geminin depletion or overexpression of Cdt1 or Cdc6 in human cells causes rereplication, a form of endogenous DNA damage. Rereplication induced by these manipulations is however uneven and incomplete, suggesting that one or more mechanisms restrain rereplication once it begins. We find that both Cdt1 and Cdc6 are degraded in geminin-depleted cells. We further show that Cdt1 degradation in cells that have rereplicated requires the PCNA binding site of Cdt1 and the Cul4(DDB1) ubiquitin ligase, and Cdt1 can induce its own degradation when overproduced. Cdc6 degradation in geminin-depleted cells requires Huwe1, the ubiquitin ligase that regulates Cdc6 after DNA damage. Moreover, perturbations that specifically disrupt Cdt1 and Cdc6 degradation in response to DNA damage exacerbate rereplication when combined with geminin depletion, and this enhanced rereplication occurs in both human cells and in Drosophila melanogaster cells. We conclude that rereplication-associated DNA damage triggers Cdt1 and Cdc6 ubiquitination and destruction, and propose that this pathway represents an evolutionarily conserved mechanism that minimizes the extent of rereplication.
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Affiliation(s)
- Jonathan R Hall
- Department of Biochemistry and Biophysics, Chapel Hill, North Carolina 27599-7260
| | - Hyun O Lee
- Department of Curriculum in Genetics and Molecular Biology, Chapel Hill, North Carolina 27599-7260
| | - Brandon D Bunker
- Department of Biochemistry and Biophysics, Chapel Hill, North Carolina 27599-7260
| | - Elizabeth S Dorn
- Department of Biochemistry and Biophysics, Chapel Hill, North Carolina 27599-7260
| | - Greg C Rogers
- Department of Biology, Chapel Hill, North Carolina 27599-7260
| | - Robert J Duronio
- Department of Curriculum in Genetics and Molecular Biology, Chapel Hill, North Carolina 27599-7260; Department of Biology, Chapel Hill, North Carolina 27599-7260; Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260
| | - Jeanette Gowen Cook
- Department of Biochemistry and Biophysics, Chapel Hill, North Carolina 27599-7260; Department of Curriculum in Genetics and Molecular Biology, Chapel Hill, North Carolina 27599-7260; Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7260.
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Martin CM, Kehoe L, Spillane CO, O'Leary JJ. Gene discovery in cervical cancer : towards diagnostic and therapeutic biomarkers. Mol Diagn Ther 2008; 11:277-90. [PMID: 17963416 DOI: 10.1007/bf03256249] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Cervical cancer is a potentially preventable disease; however, it remains the second most common malignancy in women worldwide. The human papillomavirus (HPV) is the single most important etiological agent in cervical cancer. HPV contributes to neoplastic progression through the action of two viral oncoproteins E6 and E7, which interfere with critical cell cycle pathways, tumor protein p53, and retinoblastoma protein. However, evidence suggests that HPV infection alone is insufficient to induce malignant changes, and other host genetic variations are important in the development of cervical cancer. Advances in molecular biology and high throughput technologies have heralded a new era in biomarker discovery and identification of molecular targets related to carcinogenesis. These advancements have improved our understanding of carcinogenesis and will facilitate screening, early detection, management, and personalized targeted therapy. A number of these developments and molecular targets associated with cervical cancer will be addressed in this review.
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Affiliation(s)
- Cara M Martin
- Department of Pathology, Coombe Women's Hospital, Dublin, Ireland.
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49
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Porter AC. Preventing DNA over-replication: a Cdk perspective. Cell Div 2008; 3:3. [PMID: 18211690 PMCID: PMC2245919 DOI: 10.1186/1747-1028-3-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2007] [Accepted: 01/22/2008] [Indexed: 12/24/2022] Open
Abstract
The cell cycle is tightly controlled to ensure that replication origins fire only once per cycle and that consecutive S-phases are separated by mitosis. When controls fail, DNA over-replication ensues: individual origins fire more than once per S-phase (re-replication) or consecutive S-phases occur without intervening mitoses (endoreduplication). In yeast the cell cycle is controlled by a single cyclin dependent kinase (Cdk) that prevents origin licensing at times when it promotes origin firing, and that is inactivated, via proteolysis of its partner cyclin, as cells undergo mitosis. A quantitative model describes three levels of Cdk activity: low activity allows licensing, intermediate activity allows firing but prevents licensing, and high activity promotes mitosis. In higher eukaryotes the situation is complicated by the existence of additional proteins (geminin, Cul4-Ddb1Cdt2, and Emi1) that control licensing. A current challenge is to understand how these various control mechanisms are co-ordinated and why the degree of redundancy between them is so variable. Here the experimental induction of DNA over-replication is reviewed in the context of the quantitative model of Cdk action. Endoreduplication is viewed as a consequence of procedures that cause Cdk activity to fall below the threshold required to prevent licensing, and re-replication as the result of procedures that increase that threshold value. This may help to explain why over-replication does not necessarily require reduced Cdk activity and how different mechanisms conspire to prevent over-replication. Further work is nevertheless required to determine exactly how losing just one licensing control mechanism often causes over-replication, and why this varies between cell systems.
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Affiliation(s)
- Andrew Cg Porter
- Department of Haematology, Faculty of Medicine, Imperial College London, Du Cane Road, London W12 ONN, UK.
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50
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Hook SS, Lin JJ, Dutta A. Mechanisms to control rereplication and implications for cancer. Curr Opin Cell Biol 2007; 19:663-71. [PMID: 18053699 DOI: 10.1016/j.ceb.2007.10.007] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2007] [Revised: 10/11/2007] [Accepted: 10/11/2007] [Indexed: 12/19/2022]
Abstract
Recent advances in the replication field have highlighted how the replication initiator proteins are negatively regulated by inhibitor proteins and ubiquitin-mediated degradation in mammalian cells to prevent rereplication. When these regulatory pathways go awry, uncontrolled rereplication ensues and a G2/M checkpoint is evoked to prevent cellular death. Many components of the checkpoints activated by rereplicaton are important for cancer prevention by facilitating DNA damage repair processes. The pathways that prevent rereplication themselves have also recently been implicated in preventing tumorigenesis. Studies from patient tumors, genetically altered mice, and mammalian cell culture suggest that deregulation of replication licensing proteins results in an increase in aneuploidy, chromosomal fusions, and DNA breaks. These studies provide a framework to address how regulators of replication function to maintain genomic stability.
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Affiliation(s)
- Sara S Hook
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
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