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Ghatak D, Das Ghosh D, Roychoudhury S. Cancer Stemness: p53 at the Wheel. Front Oncol 2021; 10:604124. [PMID: 33505918 PMCID: PMC7830093 DOI: 10.3389/fonc.2020.604124] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 11/18/2020] [Indexed: 12/12/2022] Open
Abstract
The tumor suppressor p53 maintains an equilibrium between self-renewal and differentiation to sustain a limited repertoire of stem cells for proper development and maintenance of tissue homeostasis. Inactivation of p53 disrupts this balance and promotes pluripotency and somatic cell reprogramming. A few reports in recent years have indicated that prevalent TP53 oncogenic gain-of-function (GOF) mutations further boosts the stemness properties of cancer cells. In this review, we discuss the role of wild type p53 in regulating pluripotency of normal stem cells and various mechanisms that control the balance between self-renewal and differentiation in embryonic and adult stem cells. We also highlight how inactivating and GOF mutations in p53 stimulate stemness in cancer cells. Further, we have explored the various mechanisms of mutant p53-driven cancer stemness, particularly emphasizing on the non-coding RNA mediated epigenetic regulation. We have also analyzed the association of cancer stemness with other crucial gain-of-function properties of mutant p53 such as epithelial to mesenchymal transition phenotypes and chemoresistance to understand how activation of one affects the other. Given the critical role of cancer stem-like cells in tumor maintenance, cancer progression, and therapy resistance of mutant p53 tumors, targeting them might improve therapeutic efficacy in human cancers with TP53 mutations.
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Affiliation(s)
- Dishari Ghatak
- Cancer Biology and Inflammatory Disorder Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - Damayanti Das Ghosh
- Division of Research, Saroj Gupta Cancer Centre and Research Institute, Kolkata, India
| | - Susanta Roychoudhury
- Division of Research, Saroj Gupta Cancer Centre and Research Institute, Kolkata, India
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2
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Abstract
The Origin Recognition Complex (ORC) is an evolutionarily conserved six-subunit protein complex that binds specific sites at many locations to coordinately replicate the entire eukaryote genome. Though highly conserved in structure, ORC’s selectivity for replication origins has diverged tremendously between yeasts and humans to adapt to vastly different life cycles. In this work, we demonstrate that the selectivity determinant of ORC for DNA binding lies in a 19-amino acid insertion helix in the Orc4 subunit, which is present in yeast but absent in human. Removal of this motif from Orc4 transforms the yeast ORC, which selects origins based on base-specific binding at defined locations, into one whose selectivity is dictated by chromatin landscape and afforded with plasticity, as reported for human. Notably, the altered yeast ORC has acquired an affinity for regions near transcriptional start sites (TSSs), which the human ORC also favors. In most model yeast species the Origin Recognition Complex (ORC) binds defined and species-specific base sequences while in humans what determines the binding appears to be more complex. Here the authors reveal that the yeast’s ORC complex binding specificity is dependent on a 19-amino acid insertion helix in the Orc4 subunit which is lost in human.
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Falbo L, Costanzo V. Epigenetic regulation of replication origin assembly: A role for histone H1 and chromatin remodeling factors. Bioessays 2020; 43:e2000181. [PMID: 33165968 DOI: 10.1002/bies.202000181] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 09/09/2020] [Accepted: 09/18/2020] [Indexed: 12/18/2022]
Abstract
During early embryonic development in several metazoans, accurate DNA replication is ensured by high number of replication origins. This guarantees rapid genome duplication coordinated with fast cell divisions. In Xenopus laevis embryos this program switches to one with a lower number of origins at a developmental stage known as mid-blastula transition (MBT) when cell cycle length increases and gene transcription starts. Consistent with this regulation, somatic nuclei replicate poorly when transferred to eggs, suggesting the existence of an epigenetic memory suppressing replication assembly origins at all available sites. Recently, it was shown that histone H1 imposes a non-permissive chromatin configuration preventing replication origin assembly on somatic nuclei. This somatic state can be erased by SSRP1, a subunit of the FACT complex. Here, we further develop the hypothesis that this novel form of epigenetic memory might impact on different areas of vertebrate biology going from nuclear reprogramming to cancer development.
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Affiliation(s)
- Lucia Falbo
- IFOM, The FIRC Institute of Molecular Oncology, Via Adamello 16, Milan, 20139, Italy
| | - Vincenzo Costanzo
- IFOM, The FIRC Institute of Molecular Oncology, Via Adamello 16, Milan, 20139, Italy.,Department of Oncology and Haematology-Oncology, University of Milan, Milan, Italy
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Yu Q, Pu SY, Wu H, Chen XQ, Jiang JJ, Gu KS, He YH, Kong QP. TICRR Contributes to Tumorigenesis Through Accelerating DNA Replication in Cancers. Front Oncol 2019; 9:516. [PMID: 31275851 PMCID: PMC6591320 DOI: 10.3389/fonc.2019.00516] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Accepted: 05/29/2019] [Indexed: 12/31/2022] Open
Abstract
DNA replication is precisely regulated in cells and its dysregulation can trigger tumorigenesis. Here we identified that the TOPBP1 interacting checkpoint and replication regulator (TICRR) mRNA level was universally and highly expressed in 15 solid cancer types. Depletion of TICRR significantly inhibited tumor cell growth, colony formation and migration in vitro, and strikingly inhibited tumor growth in the xenograft model. We reveal that knockdown of TICRR inhibited not only the initiation but also the fork progression of DNA replication. Suppression of DNA synthesis by TICRR silencing caused DNA damage accumulation, subsequently activated the ATM/CHK2 dependent p53 signaling, and finally induced cell cycle arrest and apoptosis at least in p53-wild cancer cells. Further, we show that a higher TICRR level was associated with poorer overall survival (OS) and disease free survival (DFS) in multiple cancer types. In conclusion, our study shows that TICRR is involved in tumorigenesis by regulating DNA replication, acting as a common biomarker for cancer prognosis and could be a promising target for drug-development and cancer treatment.
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Affiliation(s)
- Qin Yu
- State Key Laboratory of Genetic Resources and Evolution/Key Laboratory of Healthy Aging Research of Yunnan Province, Kunming Institute of Zoology, The Chinese Academy of Sciences, Kunming, China
- Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, China
- Kunming Key Laboratory of Healthy Aging Study, Kunming, China
- KIZ/CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, Kunming, China
- Kunming College of Life Science, University of Chinese Academy of Sciences, Beijing, China
| | - Shao-Yan Pu
- State Key Laboratory of Genetic Resources and Evolution/Key Laboratory of Healthy Aging Research of Yunnan Province, Kunming Institute of Zoology, The Chinese Academy of Sciences, Kunming, China
- Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, China
- Kunming Key Laboratory of Healthy Aging Study, Kunming, China
- KIZ/CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, Kunming, China
| | - Huan Wu
- State Key Laboratory of Genetic Resources and Evolution/Key Laboratory of Healthy Aging Research of Yunnan Province, Kunming Institute of Zoology, The Chinese Academy of Sciences, Kunming, China
- Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, China
- Kunming Key Laboratory of Healthy Aging Study, Kunming, China
- KIZ/CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, Kunming, China
| | - Xiao-Qiong Chen
- State Key Laboratory of Genetic Resources and Evolution/Key Laboratory of Healthy Aging Research of Yunnan Province, Kunming Institute of Zoology, The Chinese Academy of Sciences, Kunming, China
- Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, China
- Kunming Key Laboratory of Healthy Aging Study, Kunming, China
- KIZ/CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, Kunming, China
| | - Jian-Jun Jiang
- State Key Laboratory of Genetic Resources and Evolution/Key Laboratory of Healthy Aging Research of Yunnan Province, Kunming Institute of Zoology, The Chinese Academy of Sciences, Kunming, China
- Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, China
- Kunming Key Laboratory of Healthy Aging Study, Kunming, China
- KIZ/CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, Kunming, China
| | - Kang-Shuyun Gu
- State Key Laboratory of Genetic Resources and Evolution/Key Laboratory of Healthy Aging Research of Yunnan Province, Kunming Institute of Zoology, The Chinese Academy of Sciences, Kunming, China
- Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, China
- Kunming Key Laboratory of Healthy Aging Study, Kunming, China
- KIZ/CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, Kunming, China
- Kunming College of Life Science, University of Chinese Academy of Sciences, Beijing, China
| | - Yong-Han He
- State Key Laboratory of Genetic Resources and Evolution/Key Laboratory of Healthy Aging Research of Yunnan Province, Kunming Institute of Zoology, The Chinese Academy of Sciences, Kunming, China
- Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, China
- Kunming Key Laboratory of Healthy Aging Study, Kunming, China
- KIZ/CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, Kunming, China
| | - Qing-Peng Kong
- State Key Laboratory of Genetic Resources and Evolution/Key Laboratory of Healthy Aging Research of Yunnan Province, Kunming Institute of Zoology, The Chinese Academy of Sciences, Kunming, China
- Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, China
- Kunming Key Laboratory of Healthy Aging Study, Kunming, China
- KIZ/CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, Kunming, China
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Datta A, Ghatak D, Das S, Banerjee T, Paul A, Butti R, Gorain M, Ghuwalewala S, Roychowdhury A, Alam SK, Das P, Chatterjee R, Dasgupta M, Panda CK, Kundu GC, Roychoudhury S. p53 gain-of-function mutations increase Cdc7-dependent replication initiation. EMBO Rep 2017; 18:2030-2050. [PMID: 28887320 DOI: 10.15252/embr.201643347] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 08/04/2017] [Accepted: 08/09/2017] [Indexed: 12/31/2022] Open
Abstract
Cancer-associated p53 missense mutants confer gain of function (GOF) and promote tumorigenesis by regulating crucial signaling pathways. However, the role of GOF mutant p53 in regulating DNA replication, a commonly altered pathway in cancer, is less explored. Here, we show that enhanced Cdc7-dependent replication initiation enables mutant p53 to confer oncogenic phenotypes. We demonstrate that mutant p53 cooperates with the oncogenic transcription factor Myb in vivo and transactivates Cdc7 in cancer cells. Moreover, mutant p53 cells exhibit enhanced levels of Dbf4, promoting the activity of Cdc7/Dbf4 complex. Chromatin enrichment of replication initiation factors and subsequent increase in origin firing confirm increased Cdc7-dependent replication initiation in mutant p53 cells. Further, knockdown of CDC7 significantly abrogates mutant p53-driven cancer phenotypes in vitro and in vivo Importantly, high CDC7 expression significantly correlates with p53 mutational status and predicts poor clinical outcome in lung adenocarcinoma patients. Collectively, this study highlights a novel functional interaction between mutant p53 and the DNA replication pathway in cancer cells. We propose that increased Cdc7-dependent replication initiation is a hallmark of p53 gain-of-function mutations.
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Affiliation(s)
- Arindam Datta
- Cancer Biology and Inflammatory Disorder Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - Dishari Ghatak
- Cancer Biology and Inflammatory Disorder Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - Sumit Das
- Laboratory of Tumor Biology, Angiogenesis and Nanomedicine Research, National Centre for Cell Science (NCCS), Pune, India
| | - Taraswi Banerjee
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH Biomedical Research Center, NIH, Baltimore, MD, USA
| | - Anindita Paul
- Department of Biochemistry, University of Calcutta, Kolkata, India
| | - Ramesh Butti
- Laboratory of Tumor Biology, Angiogenesis and Nanomedicine Research, National Centre for Cell Science (NCCS), Pune, India
| | - Mahadeo Gorain
- Laboratory of Tumor Biology, Angiogenesis and Nanomedicine Research, National Centre for Cell Science (NCCS), Pune, India
| | - Sangeeta Ghuwalewala
- Cancer Biology and Inflammatory Disorder Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - Anirban Roychowdhury
- Department of Oncogene Regulation, Chittaranjan National Cancer Institute, Kolkata, India
| | - Sk Kayum Alam
- Cancer Biology and Inflammatory Disorder Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - Pijush Das
- Cancer Biology and Inflammatory Disorder Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | | | | | - Chinmay Kumar Panda
- Department of Oncogene Regulation, Chittaranjan National Cancer Institute, Kolkata, India
| | - Gopal C Kundu
- Laboratory of Tumor Biology, Angiogenesis and Nanomedicine Research, National Centre for Cell Science (NCCS), Pune, India
| | - Susanta Roychoudhury
- Cancer Biology and Inflammatory Disorder Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India .,Saroj Gupta Cancer Centre and Research Institute, Kolkata, India
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6
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Azenha D, Lopes MC, Martins TC. Claspin functions in cell homeostasis-A link to cancer? DNA Repair (Amst) 2017; 59:27-33. [PMID: 28942358 DOI: 10.1016/j.dnarep.2017.09.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 09/06/2017] [Indexed: 10/18/2022]
Abstract
Cancer remains one of the leading causes of mortality worldwide. Most cancers present high degrees of genomic instability. DNA damage and replication checkpoints function as barriers to halt cell cycle progression until damage is resolved, preventing the perpetuation of errors. Activation of these checkpoints is critically dependent on Claspin, an adaptor protein that mediates the phosphorylation of the effector kinase Chk1 by ATR. However, Claspin also performs other roles related to the protection and maintenance of cell and genome integrity. For instance, following DNA damage and checkpoint activation, Claspin bridges checkpoint responses to DNA repair or to apoptosis. During DNA replication, Claspin acts a sensor and couples DNA unwinding to strand polymerization, and may also indirectly regulate replication initiation at firing origins. As Claspin participates in several processes that are vital to maintenance of cell homeostasis, its function is tightly regulated at multiple levels. Nevertheless, little is known about its role in cancer. Accumulating evidence suggests that Claspin inactivation could be an essential event during carcinogenesis, indicating that Claspin may function as a tumour suppressor. In this review, we will examine the functions of Claspin and how its deregulation may contribute to cancer initiation and progression. To conclude, we will discuss means by which Claspin can be targeted for cancer therapy.
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Affiliation(s)
- Diana Azenha
- Faculdade de Farmácia da Universidade de Coimbra, Pólo das Ciências da Saúde, Azinhaga de Santa Comba, 3000-548 Coimbra, Portugal; Centro de Neurociências e Biologia Celular, Universidade de Coimbra, Rua Larga, Faculdade de Medicina, Pólo I, 1º andar, 3004-504 Coimbra, Portugal; Instituto Português de Oncologia de Coimbra de Francisco Gentil, Av. Bissaya Barreto 98, Apartado 2005, 3000-651, Coimbra, Portugal.
| | - Maria Celeste Lopes
- Faculdade de Farmácia da Universidade de Coimbra, Pólo das Ciências da Saúde, Azinhaga de Santa Comba, 3000-548 Coimbra, Portugal; Centro de Neurociências e Biologia Celular, Universidade de Coimbra, Rua Larga, Faculdade de Medicina, Pólo I, 1º andar, 3004-504 Coimbra, Portugal.
| | - Teresa C Martins
- Centro de Neurociências e Biologia Celular, Universidade de Coimbra, Rua Larga, Faculdade de Medicina, Pólo I, 1º andar, 3004-504 Coimbra, Portugal; Instituto Português de Oncologia de Coimbra de Francisco Gentil, Av. Bissaya Barreto 98, Apartado 2005, 3000-651, Coimbra, Portugal.
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7
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Valenzuela MS, Green N, Liu S. Identification of Berenil Target Sites in Plasmid pBR322. INTERNATIONAL JOURNAL OF BIOORGANIC CHEMISTRY & MOLECULAR BIOLOGY 2017; 5:24-30. [PMID: 29104898 PMCID: PMC5667686 DOI: 10.19070/2332-2756-170004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Berenil, a minor groove DNA binding molecule, has been extensively used in veterinary medicine. Modeling studies have suggested that berenil binds to A/T rich regions on the DNA and the product of this interaction causes the formation of crosslinks between opposite DNA strands. These crosslinks could potentially inhibit fundamental biological processes including transcription and DNA replication. We had previously used the pBR322 genome as a model system to investigate the role of A/T sequences on berenil activity. We reported that the insertion of poly(dA)poly(dT) sequences into the pBR322 genome causes replication inhibition of the recombinant plasmids when cultures were exposed to berenil. However, we noticed that even in the absence of these sequences the parental plasmid replication was also inhibited, albeit less than the recombinants. This observation led us to the present study were we attempted to identify the location of natural berenil target sites in the pBR322 genome. Through a combination of deletion analysis, recombinant DNA and a replication assay we uncovered a 378 bp DNA fragment that has all the hallmarks of a berenil target site. A recombinant plasmid lacking this region is more refractive to the drug than the parental plasmid, and another variant containing and extra copy of this region increases the susceptibility of the plasmid towards berenil. The 378 bp region is about 60% A/T rich and contains about 21 potential berenil binding sites.
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Affiliation(s)
- MS Valenzuela
- Department of Biochemistry and Cancer Biology, School of Medicine, Meharry Medical College, 1005 DB Todd Jr. BIvd, Nashville, TN, USA
| | - N Green
- Department of Biochemistry and Cancer Biology, School of Medicine, Meharry Medical College, 1005 DB Todd Jr. BIvd, Nashville, TN, USA
| | - S Liu
- Department of Biochemistry and Cancer Biology, School of Medicine, Meharry Medical College, 1005 DB Todd Jr. BIvd, Nashville, TN, USA
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8
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Raspelli E, Falbo L, Costanzo V. Xenopus egg extract to study regulation of genome-wide and locus-specific DNA replication. Genesis 2017; 55. [PMID: 28095613 DOI: 10.1002/dvg.22996] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Revised: 11/10/2016] [Accepted: 11/10/2016] [Indexed: 11/10/2022]
Abstract
Faithful DNA replication, coupled with accurate repair of DNA damage, is essential to maintain genome stability and relies on different DNA metabolism genes. Many of these genes are involved in the assembly of replication origins, in the coordination of DNA repair to protect replication forks progression in the presence of DNA damage and in the replication of repetitive chromatin regions. Some DNA metabolism genes are essential in higher eukaryotes, suggesting the existence of specialized mechanisms of repair and replication in organisms with complex genomes. The impact on cell survival of many of these genes has so far precluded in depth molecular analysis of their function. The cell-free Xenopus laevis egg extract represents an ideal system to overcome survival issues and to facilitate the biochemical study of replication-associated functions of essential proteins in vertebrate organisms. Here, we will discuss how Xenopus egg extracts have been used to study cellular and molecular processes, such as DNA replication and DNA repair. In particular, we will focus on innovative imaging and proteomic-based experimental approaches to characterize the molecular function of a number of essential DNA metabolism factors involved in the duplication of complex vertebrate genomes.
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Affiliation(s)
- Erica Raspelli
- DNA metabolism laboratory, IFOM, The FIRC institute for Molecular Oncology, Milan, Italy
| | - Lucia Falbo
- DNA metabolism laboratory, IFOM, The FIRC institute for Molecular Oncology, Milan, Italy
| | - Vincenzo Costanzo
- DNA metabolism laboratory, IFOM, The FIRC institute for Molecular Oncology, Milan, Italy
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9
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Gindin Y, Meltzer PS, Bilke S. Replicon: a software to accurately predict DNA replication timing in metazoan cells. Front Genet 2014; 5:378. [PMID: 25404939 PMCID: PMC4217517 DOI: 10.3389/fgene.2014.00378] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Accepted: 10/13/2014] [Indexed: 02/05/2023] Open
Abstract
Eukaryotic DNA replication follows a strict temporal program where genomic loci are replicated at precise times during the S phase of the cell cycle. Yet, the mechanism in control of the timing program in metazoan cells is poorly understood. In a recent publication, the authors proposed an intuitive stochastic model of DNA replication and showed that it predicts replication timing with an accuracy approaching the level of experimental biological repeats. Here, we discuss an extended software implementation of the mechanistic model: Replicon. This package allows interested researchers to predict the global replication timing program in human cells from chromatin data.
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Affiliation(s)
- Yevgeniy Gindin
- Genetics Branch, Center for Cancer Research, National Institutes of Health Bethesda, MD, USA ; Graduate Program in Bioinformatics, Boston University Boston, MA, USA
| | - Paul S Meltzer
- Genetics Branch, Center for Cancer Research, National Institutes of Health Bethesda, MD, USA
| | - Sven Bilke
- Genetics Branch, Center for Cancer Research, National Institutes of Health Bethesda, MD, USA
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10
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Champeris Tsaniras S, Kanellakis N, Symeonidou IE, Nikolopoulou P, Lygerou Z, Taraviras S. Licensing of DNA replication, cancer, pluripotency and differentiation: an interlinked world? Semin Cell Dev Biol 2014; 30:174-80. [PMID: 24641889 DOI: 10.1016/j.semcdb.2014.03.013] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 03/10/2014] [Indexed: 01/06/2023]
Abstract
Recent findings provide evidence for a functional interplay between DNA replication and the seemingly distinct areas of cancer, development and pluripotency. Protein complexes participating in DNA replication origin licensing are now known to have roles in development, while their deregulation can lead to cancer. Moreover, transcription factors implicated in the maintenance of or reversal to the pluripotent state have links to the pre-replicative machinery. Several studies have shown that overexpression of these factors is associated to cancer.
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Affiliation(s)
- S Champeris Tsaniras
- Department of Physiology, Medical School, University of Patras, Rio, 26504 Patras, Greece.
| | - N Kanellakis
- Department of Physiology, Medical School, University of Patras, Rio, 26504 Patras, Greece.
| | - I E Symeonidou
- Department of Biology, Medical School, University of Patras, Rio, 26504 Patras, Greece.
| | - P Nikolopoulou
- Department of Physiology, Medical School, University of Patras, Rio, 26504 Patras, Greece.
| | - Z Lygerou
- Department of Biology, Medical School, University of Patras, Rio, 26504 Patras, Greece.
| | - S Taraviras
- Department of Physiology, Medical School, University of Patras, Rio, 26504 Patras, Greece.
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11
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Di Paola D, Rampakakis E, Chan MK, Zannis-Hadjopoulos M. Differential chromatin structure encompassing replication origins in transformed and normal cells. Genes Cancer 2012; 3:152-76. [PMID: 23050047 DOI: 10.1177/1947601912457026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Accepted: 07/10/2012] [Indexed: 12/23/2022] Open
Abstract
This study examines the chromatin structure encompassing replication origins in transformed and normal cells. Analysis of the global levels of histone H3 acetylated at K9&14 (open chromatin) and histone H3 trimethylated at K9 (closed chromatin) revealed a higher ratio of open to closed chromatin in the transformed cells. Also, the trithorax and polycomb group proteins, Brg-1 and Bmi-1, respectively, were overexpressed and more abundantly bound to chromatin in the transformed cells. Quantitative comparative analyses of episomal and in situ chromosomal replication origin activity as well as chromatin immunoprecipitation (ChIP) assays, using specific antibodies targeting members of the pre-replication complex (pre-RC) as well as open/closed chromatin markers encompassing both episomal and chromosomal origins, revealed that episomal origins had similar levels of in vivo activity, nascent DNA abundance, pre-RC protein association, and elevated open chromatin structure at the origin in both cell types. In contrast, the chromosomal origins corresponding to 20mer1, 20mer2, and c-myc displayed a 2- to 3-fold higher activity and pre-RC protein abundance as well as higher ratios of open to closed chromatin and of Brg-1 to Bmi-1 in the transformed cells, whereas the origin associated with the housekeeping lamin B2 gene exhibited similar levels of activity, pre-RC protein abundance, and higher ratios of open to closed chromatin and of Brg-1 to Bmi-1 in both cell types. Nucleosomal positioning analysis, using an MNase-Southern blot assay, showed that all the origin regions examined were situated within regions of inconsistently positioned nucleosomes, with the nucleosomes being spaced farther apart from each other prior to the onset of S phase in both cell types. Overall, the results indicate that cellular transformation is associated with differential epigenetic regulation, whereby chromatin structure is more open, rendering replication origins more accessible to initiator proteins, thus allowing increased origin activity.
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Affiliation(s)
- Domenic Di Paola
- Goodman Cancer Center and Department of Biochemistry, McGill University, Montreal, Quebec, Canada
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12
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Valenzuela MS. Initiation of DNA Replication in the Human Genome. HEREDITARY GENETICS : CURRENT RESEARCH 2012; Suppl 1:4903. [PMID: 24511453 PMCID: PMC3915928 DOI: 10.4172/2161-1041.s1-003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Replication of the human genome relies on the presence of thousands of origins distributed along each of the chromosomes. The activation of these origins occurs in a highly regulated manner to ensure that chromosomes are faithfully duplicated only once during each cell cycle. Failure in this regulation can lead to abnormal cell proliferation, or/and genomic instability, the hallmarks of cancer cells. The mechanisms determining how, when, and where origins are activated remains still a mystery. However recent technological advances have facilitated the study of DNA replication in a genome-wide scale, and have provided a wealth of information on several features of this process. Here we present an overview of the current progress on our understanding of the initiation step of DNA replication in human cells, and its relationship to abnormal cell proliferation.
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Affiliation(s)
- Manuel S. Valenzuela
- Department of Biochemistry and Cancer Biology, School of Medicine, Meharry Medical College, 1005 D.B. Todd Jr. Boulevard, Nashville, TN 37208, USA
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