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Xun Q, Song Y, Mei M, Ding Y, Ding C. The SMC5/6 complex subunit MMS21 regulates stem cell proliferation in rice. PLANT CELL REPORTS 2023:10.1007/s00299-023-03030-9. [PMID: 37178216 DOI: 10.1007/s00299-023-03030-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Accepted: 05/04/2023] [Indexed: 05/15/2023]
Abstract
KEY MESSAGE SMC5/6 complex subunit OsMMS21 is involved in cell cycle and hormone signaling and required for stem cell proliferation during shoot and root development in rice. The structural maintenance of chromosome (SMC)5/6 complex is required for nucleolar integrity and DNA metabolism. Moreover, METHYL METHANESULFONATE SENSITIVITY GENE 21 (MMS21), a SUMO E3 ligase that is part of the SMC5/6 complex, is essential for the root stem cell niche and cell cycle transition in Arabidopsis. However, its specific role in rice remains unclear. Here, OsSMC5 and OsSMC6 single heterozygous mutants were generated using CRISPR/Cas9 technology to elucidate the function of SMC5/6 subunits, including OsSMC5, OsSMC6, and OsMMS21, in cell proliferation in rice. ossmc5/ + and ossmc6/ + heterozygous single mutants did not yield homozygous mutants in their progeny, indicating that OsSMC5 and OsSMC6 both play necessary roles during embryo formation. Loss of OsMMS21 caused severe defects in both the shoot and roots in rice. Transcriptome analysis showed a significant decrease in the expression of genes involved in auxin signaling in the roots of osmms21 mutants. Moreover, the expression levels of the cycB2-1 and MCM genes, which are involved the cell cycle, were significantly lower in the shoots of the mutants, indicating that OsMMS21 was involved in both hormone signaling pathways and the cell cycle. Overall, these findings indicate that the SUMO E3 ligase OsMMS21 is required for both shoot and root stem cell niches, improving the understanding of the function of the SMC5/6 complex in rice.
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Affiliation(s)
- Qian Xun
- College of Agriculture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Ye Song
- College of Agriculture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Min Mei
- College of Agriculture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Yanfeng Ding
- College of Agriculture, Nanjing Agricultural University, Nanjing, 210095, China
- Key Laboratory of Crop Physiology Ecology and Production Management, Ministry of Agriculture, Nanjing, 210095, China
- Jiangsu Collaborative Innovation Centre for Modern Crop Production, Nanjing, 210095, China
| | - Chengqiang Ding
- College of Agriculture, Nanjing Agricultural University, Nanjing, 210095, China.
- Key Laboratory of Crop Physiology Ecology and Production Management, Ministry of Agriculture, Nanjing, 210095, China.
- Jiangsu Collaborative Innovation Centre for Modern Crop Production, Nanjing, 210095, China.
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MCM2 in human cancer: functions, mechanisms, and clinical significance. Mol Med 2022; 28:128. [PMID: 36303105 PMCID: PMC9615236 DOI: 10.1186/s10020-022-00555-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Accepted: 10/10/2022] [Indexed: 11/18/2022] Open
Abstract
Background Aberrant DNA replication is the main source of genomic instability that leads to tumorigenesis and progression. MCM2, a core subunit of eukaryotic helicase, plays a vital role in DNA replication. The dysfunction of MCM2 results in the occurrence and progression of multiple cancers through impairing DNA replication and cell proliferation. Conclusions MCM2 is a vital regulator in DNA replication. The overexpression of MCM2 was detected in multiple types of cancers, and the dysfunction of MCM2 was correlated with the progression and poor prognoses of malignant tumors. According to the altered expression of MCM2 and its correlation with clinicopathological features of cancer patients, MCM2 was thought to be a sensitive biomarker for cancer diagnosis, prognosis, and chemotherapy response. The anti-tumor effect induced by MCM2 inhibition implies the potential of MCM2 to be a novel therapeutic target for cancer treatment. Since DNA replication stress, which may stimulate anti-tumor immunity, frequently occurs in MCM2 deficient cells, it also proposes the possibility that MCM2 targeting improves the effect of tumor immunotherapy.
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Hulke ML, Massey DJ, Koren A. Genomic methods for measuring DNA replication dynamics. Chromosome Res 2020; 28:49-67. [PMID: 31848781 PMCID: PMC7131883 DOI: 10.1007/s10577-019-09624-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 11/30/2019] [Accepted: 12/03/2019] [Indexed: 12/27/2022]
Abstract
Genomic DNA replicates according to a defined temporal program in which early-replicating loci are associated with open chromatin, higher gene density, and increased gene expression levels, while late-replicating loci tend to be heterochromatic and show higher rates of genomic instability. The ability to measure DNA replication dynamics at genome scale has proven crucial for understanding the mechanisms and cellular consequences of DNA replication timing. Several methods, such as quantification of nucleotide analog incorporation and DNA copy number analyses, can accurately reconstruct the genomic replication timing profiles of various species and cell types. More recent developments have expanded the DNA replication genomic toolkit to assays that directly measure the activity of replication origins, while single-cell replication timing assays are beginning to reveal a new level of replication timing regulation. The combination of these methods, applied on a genomic scale and in multiple biological systems, promises to resolve many open questions and lead to a holistic understanding of how eukaryotic cells replicate their genomes accurately and efficiently.
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Affiliation(s)
- Michelle L Hulke
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA
| | - Dashiell J Massey
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA
| | - Amnon Koren
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA.
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Casar Tena T, Maerz LD, Szafranski K, Groth M, Blätte TJ, Donow C, Matysik S, Walther P, Jeggo PA, Burkhalter MD, Philipp M. Resting cells rely on the DNA helicase component MCM2 to build cilia. Nucleic Acids Res 2019; 47:134-151. [PMID: 30329080 PMCID: PMC6326816 DOI: 10.1093/nar/gky945] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2018] [Accepted: 10/04/2018] [Indexed: 12/24/2022] Open
Abstract
Minichromosome maintenance (MCM) proteins facilitate replication by licensing origins and unwinding the DNA double strand. Interestingly, the number of MCM hexamers greatly exceeds the number of firing origins suggesting additional roles of MCMs. Here we show a hitherto unanticipated function of MCM2 in cilia formation in human cells and zebrafish that is uncoupled from replication. Zebrafish depleted of MCM2 develop ciliopathy-phenotypes including microcephaly and aberrant heart looping due to malformed cilia. In non-cycling human fibroblasts, loss of MCM2 promotes transcription of a subset of genes, which cause cilia shortening and centriole overduplication. Chromatin immunoprecipitation experiments show that MCM2 binds to transcription start sites of cilia inhibiting genes. We propose that such binding may block RNA polymerase II-mediated transcription. Depletion of a second MCM (MCM7), which functions in complex with MCM2 during its canonical functions, reveals an overlapping cilia-deficiency phenotype likely unconnected to replication, although MCM7 appears to regulate a distinct subset of genes and pathways. Our data suggests that MCM2 and 7 exert a role in ciliogenesis in post-mitotic tissues.
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Affiliation(s)
- Teresa Casar Tena
- Institute of Biochemistry and Molecular Biology, Ulm University, 89081 Ulm, Germany
| | - Lars D Maerz
- Institute of Biochemistry and Molecular Biology, Ulm University, 89081 Ulm, Germany
| | - Karol Szafranski
- Leibniz Institute on Aging, Fritz Lipmann Institute, 07745 Jena, Germany
| | - Marco Groth
- Leibniz Institute on Aging, Fritz Lipmann Institute, 07745 Jena, Germany
| | - Tamara J Blätte
- Institute of Biochemistry and Molecular Biology, Ulm University, 89081 Ulm, Germany
| | - Cornelia Donow
- Institute of Biochemistry and Molecular Biology, Ulm University, 89081 Ulm, Germany
| | - Sabrina Matysik
- Institute of Biochemistry and Molecular Biology, Ulm University, 89081 Ulm, Germany
| | - Paul Walther
- Central Facility for Electron Microscopy, Ulm University, 89081 Ulm, Germany
| | - Penelope A Jeggo
- Genome Damage and Stability Centre, University of Sussex, Brighton BN1 9RQ, UK
| | - Martin D Burkhalter
- Institute of Biochemistry and Molecular Biology, Ulm University, 89081 Ulm, Germany
| | - Melanie Philipp
- Institute of Biochemistry and Molecular Biology, Ulm University, 89081 Ulm, Germany
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Deng M, Sun J, Xie S, Zhen H, Wang Y, Zhong A, Zhang H, Lu R, Guo L. Inhibition of MCM2 enhances the sensitivity of ovarian cancer cell to carboplatin. Mol Med Rep 2019; 20:2258-2266. [PMID: 31322224 PMCID: PMC6691261 DOI: 10.3892/mmr.2019.10477] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 05/03/2019] [Indexed: 01/29/2023] Open
Abstract
Chemotherapy is widely used for the treatment of ovarian cancer. Since chemotherapy resistance is the major cause of poor prognosis in patients with ovarian cancer, it is important to identify new methods to improve the efficacy of chemotherapy. Minichromosome maintenance complex component 2 (MCM2), which serves an essential role in DNA replication, has been recently identified as a novel proliferation marker with prognostic implications in multiple types of cancer. However, the role of MCM2 in ovarian cancer and its underlying molecular mechanisms remain unclear. Therefore, in the present study, the biological effects of MCM2 were investigated, particularly with respect to DNA damage and repair. In the present study, short hairpin RNA was employed to knockdown MCM2 expression in the A2780 ovarian cancer cell line. The sensitivity of A2780 cells to carboplatin was assessed by cell colony formation assay. The present results suggested that MCM2 knockdown inhibited the proliferation of tumor cells, induced G0/G1 phase arrest and did not exhibit effects on cell apoptosis. However, MCM2 knockdown significantly decreased the colony formation of A2780 cells treated with carboplatin. Furthermore, knockdown of MCM2 together with carboplatin treatment or UV irradiation increased the protein expression level of γ-H2A histone family member X and p53 compared with control cells. The present data suggested that the increased sensitivity to carboplatin may occur via the p53-dependent apoptotic response. Additionally, the present results suggested that knockdown of MCM2 may have therapeutic applications in enhancing the efficacy of carboplatin in patients with ovarian cancer.
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Affiliation(s)
- Minjie Deng
- Department of Clinical Laboratory, Fudan University Shanghai Cancer Center, Shanghai 200032, P.R. China
| | - Jiajun Sun
- Department of Clinical Laboratory, Fudan University Shanghai Cancer Center, Shanghai 200032, P.R. China
| | - Suhong Xie
- Department of Clinical Laboratory, Fudan University Shanghai Cancer Center, Shanghai 200032, P.R. China
| | - Hui Zhen
- Department of Clinical Laboratory, Fudan University Shanghai Cancer Center, Shanghai 200032, P.R. China
| | - Yanchun Wang
- Department of Clinical Laboratory, Fudan University Shanghai Cancer Center, Shanghai 200032, P.R. China
| | - Ailing Zhong
- Department of Clinical Laboratory, Fudan University Shanghai Cancer Center, Shanghai 200032, P.R. China
| | - Hongqin Zhang
- Department of Clinical Laboratory, Fudan University Shanghai Cancer Center, Shanghai 200032, P.R. China
| | - Renquan Lu
- Department of Clinical Laboratory, Fudan University Shanghai Cancer Center, Shanghai 200032, P.R. China
| | - Lin Guo
- Department of Clinical Laboratory, Fudan University Shanghai Cancer Center, Shanghai 200032, P.R. China
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Petropoulos M, Champeris Tsaniras S, Taraviras S, Lygerou Z. Replication Licensing Aberrations, Replication Stress, and Genomic Instability. Trends Biochem Sci 2019; 44:752-764. [PMID: 31054805 DOI: 10.1016/j.tibs.2019.03.011] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 03/24/2019] [Accepted: 03/27/2019] [Indexed: 01/07/2023]
Abstract
Strict regulation of DNA replication is of fundamental significance for the maintenance of genome stability. Licensing of origins of DNA replication is a critical event for timely genome duplication. Errors in replication licensing control lead to genomic instability across evolution. Here, we present accumulating evidence that aberrant replication licensing is linked to oncogene-induced replication stress and poses a major threat to genome stability, promoting tumorigenesis. Oncogene activation can lead to defects in where along the genome and when during the cell cycle licensing takes place, resulting in replication stress. We also discuss the potential of replication licensing as a specific target for novel anticancer therapies.
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Affiliation(s)
- Michalis Petropoulos
- Department of Biology, School of Medicine, University of Patras, Patras 26504, Greece
| | | | - Stavros Taraviras
- Department of Physiology, School of Medicine, University of Patras, Patras 26504, Greece.
| | - Zoi Lygerou
- Department of Biology, School of Medicine, University of Patras, Patras 26504, Greece.
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Gao W, Wang X, Li F, Shi W, Li H, Zeng Q. Cho/Cr ratio at MR spectroscopy as a biomarker for cellular proliferation activity and prognosis in glioma: correlation with the expression of minichromosome maintenance protein 2. Acta Radiol 2019; 60:106-112. [PMID: 29665708 DOI: 10.1177/0284185118770899] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
BACKGROUND Magnetic resonance (MR) spectroscopy (1H-MRS) has been demonstrated to be useful in grading glioma, but the utility in assessing cellular proliferation activity and prognosis correlated with the expression of minichromosome maintenance protein 2 (MCM2) has not been reported. PURPOSE To explore the correlation between proton MR spectroscopy parameters (including choline [Cho]/creatine [Cr], N-acetyl aspartate [NAA]/Cr, and Cho/NAA ratios) and the expression of MCM2 and to further evaluate whether 1H-MRS can predict cell proliferative activity and provide prognostic information in high-grade gliomas (HGGs). MATERIAL AND METHODS Forty-three patients with histopathologically confirmed gliomas were involved in this study. All patients underwent 1H-MRS examination before surgery. Proliferative activity of gliomas was evaluated by MCM2 labeling index (LI). Pearson correlation analysis and empiric receiver operating characteristic (ROC) curves were performed. The Kaplan-Meier method and Cox regression were used for survival analysis. RESULTS Significant correlation was observed between the Cho/Cr ratio and MCM2 LI ( r = 0.522, P < 0.01); however, there was no correlation between MCM2 LI and the Cho/NAA or NAA/Cr ratios ( r = 0.295, P = 0.55 and r = -0.042, P = 0.788, respectively). According to ROC analysis, MCM2 LI of 50% and Cho/Cr ratio of 2.68 represented the optimized cut-off values, respectively, to distinguish longer or shorter survival than 15 months in HGGs patients. Multivariate analysis revealed that both the Cho/Cr ratio and MCM2 expression were independent prognostic markers. CONCLUSION Cho/Cr ratio has a potential in predicting the expression of MCM2 and can evaluate cell proliferative activity noninvasively. Both the Cho/Cr ratio and MCM2 expression are independent prognostic markers in patients with HGGs.
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Affiliation(s)
- Wenjing Gao
- Department of Radiology, Qilu Hospital of Shandong University, Jinan, Shandong Province, PR China
| | - Xiao Wang
- Department of Radiology, Qilu Hospital of Shandong University, Jinan, Shandong Province, PR China
| | - Fuyan Li
- Department of Radiology, Shandong Medical Imaging Research Institute, Jinan, Shandong Province, PR China
| | - Wenqi Shi
- Department of Radiology, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou Province, PR China
| | - Hongxia Li
- Department of Radiology, The Second Hospital of Shandong University, Jinan, Shandong Province, PR China
| | - Qingshi Zeng
- Department of Radiology, Qilu Hospital of Shandong University, Jinan, Shandong Province, PR China
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Liao X, Han C, Wang X, Huang K, Yu T, Yang C, Huang R, Liu Z, Han Q, Peng T. Prognostic value of minichromosome maintenance mRNA expression in early-stage pancreatic ductal adenocarcinoma patients after pancreaticoduodenectomy. Cancer Manag Res 2018; 10:3255-3271. [PMID: 30233242 PMCID: PMC6130532 DOI: 10.2147/cmar.s171293] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Background The aim of the current study was to investigate the potential prognostic value of minichromosome maintenance (MCM) genes in patients with early-stage pancreatic ductal adenocarcinoma (PDAC) after pancreaticoduodenectomy by using the RNA-sequencing dataset from The Cancer Genome Atlas (TCGA). Methods An RNA-sequencing dataset of 112 early-stage PDAC patients who received a pancreaticoduodenectomy was obtained from TCGA. Survival analysis was used to identify potential prognostic values of MCM genes in PDAC overall survival (OS). Results Through mining public databases, we observed that MCM genes (MCM2, MCM3, MCM4, MCM5, MCM6, and MCM7) were upregulated in pancreatic cancer tumor tissue and have a strong positive coexpression with each other. Multivariate survival analysis indicated that a high expression of MCM4 significantly increased the risk of death in patients with PDAC, and time-dependent receiver operating characteristic analysis showed an area under the curve of 0.655, 0.587, and 0.509 for a 1-, 2-, and 3-year PDAC OS prediction, respectively. Comprehensive survival analysis of MCM4 using stratified and joint effects survival analysis suggests that MCM4 may be an independent prognostic indicator for PDAC OS. Gene set enrichment analysis indicated that MCM4 may participate in multiple biologic processes and pathways, including DNA replication, cell cycle, tumor protein p53, and Notch signaling pathways, thereby affecting prognosis of PDAC patients. Conclusions Our study indicates that MCM2–7 were upregulated in pancreatic cancer tumor tissues, and mRNA expression of MCM4 may serve as an independent prognostic indicator for PDAC OS prediction after pancreaticoduodenectomy.
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Affiliation(s)
- Xiwen Liao
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Zhuang Autonomous Region, People's Republic of China,
| | - Chuangye Han
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Zhuang Autonomous Region, People's Republic of China,
| | - Xiangkun Wang
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Zhuang Autonomous Region, People's Republic of China,
| | - Ketuan Huang
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Zhuang Autonomous Region, People's Republic of China,
| | - Tingdong Yu
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Zhuang Autonomous Region, People's Republic of China,
| | - Chengkun Yang
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Zhuang Autonomous Region, People's Republic of China,
| | - Rui Huang
- Department of Hematology, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Zhuang Autonomous Region, People's Republic of China
| | - Zhengqian Liu
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Zhuang Autonomous Region, People's Republic of China,
| | - Quanfa Han
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Zhuang Autonomous Region, People's Republic of China,
| | - Tao Peng
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Zhuang Autonomous Region, People's Republic of China,
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Kucherlapati M. Examining transcriptional changes to DNA replication and repair factors over uveal melanoma subtypes. BMC Cancer 2018; 18:818. [PMID: 30107825 PMCID: PMC6092802 DOI: 10.1186/s12885-018-4705-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 07/30/2018] [Indexed: 12/20/2022] Open
Abstract
Background Uncontrolled replication is a process common to all cancers facilitated by the summation of changes accumulated as tumors progress. The aim of this study was to examine small groups of genes with known biology in replication and repair at the transcriptional and genomic levels, correlating alterations with survival in uveal melanoma tumor progression. Selected components of Pre-Replication, Pre-Initiation, and Replisome Complexes, DNA Damage Response and Mismatch Repair have been observed. Methods Two groups have been generated for selected genes above and below the average alteration level and compared for expression and survival across The Cancer Genome Atlas uveal melanoma subtypes. Significant differences in expression between subtypes monosomic or disomic for chromosome 3 have been identified by Fisher’s exact test. Kaplan Meier survival distribution based on disease specific survival has been compared by Log-rank test. Results Genes with significant alteration include MCM2, MCM4, MCM5, CDC45, MCM10, CIZ1, PCNA, FEN1, LIG1, POLD1, POLE, HUS1, CHECK1, ATRIP, MLH3, and MSH6. Exon 4 skipping in CIZ1 previously identified as a cancer variant, and reportedly used as an early serum biomarker in lung cancer was found. Mismatch Repair protein MLH3 was found to have splicing variations with deletions to both Exon 5 and Exon 7 simultaneously. PCNA, FEN1, and LIG1 had increased relative expression levels not due to mutation or to copy number variation. Conclusion The current study proposes changes in relative and differential expression to replication and repair genes that support the concept their products are causally involved in uveal melanoma. Specific avenues for early biomarker identification and therapeutic approach are suggested.
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Affiliation(s)
- Melanie Kucherlapati
- Department of Genetics, Harvard Medical School, Boston, 02115, MA, USA. .,Department of Medicine, Division of Genetics, Brigham and Women's Hospital, 77 Avenue Louis Pasteur NRB 160B, Boston, 02115, MA, USA.
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10
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Tian T, Chen YQ, Wang SR, Zhou X. G-Quadruplex: A Regulator of Gene Expression and Its Chemical Targeting. Chem 2018. [DOI: 10.1016/j.chempr.2018.02.014] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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DNA Replication Origins in Immunoglobulin Switch Regions Regulate Class Switch Recombination in an R-Loop-Dependent Manner. Cell Rep 2017; 17:2927-2942. [PMID: 27974207 DOI: 10.1016/j.celrep.2016.11.041] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 09/07/2016] [Accepted: 11/11/2016] [Indexed: 11/22/2022] Open
Abstract
Class switch recombination (CSR) at the immunoglobulin heavy chain (IgH) locus generates antibody isotypes. CSR depends on double-strand breaks (DSBs) induced by activation-induced cytidine deaminase (AID). Although DSB formation and repair machineries are active in G1 phase, efficient CSR is dependent on cell proliferation and S phase entry; however, the underlying mechanisms are obscure. Here, we show that efficient CSR requires the replicative helicase, the Mcm complex. Mcm proteins are enriched at IgH switch regions during CSR, leading to assembly of facultative replication origins that require Mcm helicase function for productive CSR. Assembly of CSR-associated origins is facilitated by R loops and promotes the physical proximity (synapsis) of recombining switch regions, which is reduced by R loop inhibition or Mcm complex depletion. Thus, R loops contribute to replication origin specification that promotes DSB resolution in CSR. This suggests a mechanism for the dependence of CSR on S phase and cell division.
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12
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DNA replication stress restricts ribosomal DNA copy number. PLoS Genet 2017; 13:e1007006. [PMID: 28915237 PMCID: PMC5617229 DOI: 10.1371/journal.pgen.1007006] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2017] [Revised: 09/27/2017] [Accepted: 09/05/2017] [Indexed: 12/16/2022] Open
Abstract
Ribosomal RNAs (rRNAs) in budding yeast are encoded by ~100–200 repeats of a 9.1kb sequence arranged in tandem on chromosome XII, the ribosomal DNA (rDNA) locus. Copy number of rDNA repeat units in eukaryotic cells is maintained far in excess of the requirement for ribosome biogenesis. Despite the importance of the repeats for both ribosomal and non-ribosomal functions, it is currently not known how “normal” copy number is determined or maintained. To identify essential genes involved in the maintenance of rDNA copy number, we developed a droplet digital PCR based assay to measure rDNA copy number in yeast and used it to screen a yeast conditional temperature-sensitive mutant collection of essential genes. Our screen revealed that low rDNA copy number is associated with compromised DNA replication. Further, subculturing yeast under two separate conditions of DNA replication stress selected for a contraction of the rDNA array independent of the replication fork blocking protein, Fob1. Interestingly, cells with a contracted array grew better than their counterparts with normal copy number under conditions of DNA replication stress. Our data indicate that DNA replication stresses select for a smaller rDNA array. We speculate that this liberates scarce replication factors for use by the rest of the genome, which in turn helps cells complete DNA replication and continue to propagate. Interestingly, tumors from mini chromosome maintenance 2 (MCM2)-deficient mice also show a loss of rDNA repeats. Our data suggest that a reduction in rDNA copy number may indicate a history of DNA replication stress, and that rDNA array size could serve as a diagnostic marker for replication stress. Taken together, these data begin to suggest the selective pressures that combine to yield a “normal” rDNA copy number. Eukaryotic genomes contain many copies of ribosomal DNA (rDNA) genes, usually far in excess of the requirement for cellular ribosome biogenesis. rDNA array size is highly variable, both within and across species. Although it is becoming increasingly evident that the rDNA locus serves extra-coding functions, and several pathways that contribute to maintenance of normal rDNA copy number have been discovered, the mechanisms that determine optimal rDNA array size in a cell remain unknown. Here we identify DNA replication stress as one factor that restricts rDNA copy number. We present evidence suggesting that DNA replication stress selects for cells with smaller rDNA arrays, and that contraction of the rDNA array provides a selective advantage to cells under conditions of DNA replication stress. Loss of rDNA copies may be a useful indicator of a history of replication stress, as observed in a mouse model for cancer.
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13
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Hamperl S, Bocek MJ, Saldivar JC, Swigut T, Cimprich KA. Transcription-Replication Conflict Orientation Modulates R-Loop Levels and Activates Distinct DNA Damage Responses. Cell 2017; 170:774-786.e19. [PMID: 28802045 DOI: 10.1016/j.cell.2017.07.043] [Citation(s) in RCA: 367] [Impact Index Per Article: 52.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2017] [Revised: 05/09/2017] [Accepted: 07/25/2017] [Indexed: 12/19/2022]
Abstract
Conflicts between transcription and replication are a potent source of DNA damage. Co-transcriptional R-loops could aggravate such conflicts by creating an additional barrier to replication fork progression. Here, we use a defined episomal system to investigate how conflict orientation and R-loop formation influence genome stability in human cells. R-loops, but not normal transcription complexes, induce DNA breaks and orientation-specific DNA damage responses during conflicts with replication forks. Unexpectedly, the replisome acts as an orientation-dependent regulator of R-loop levels, reducing R-loops in the co-directional (CD) orientation but promoting their formation in the head-on (HO) orientation. Replication stress and deregulated origin firing increase the number of HO collisions leading to genome-destabilizing R-loops. Our findings connect DNA replication to R-loop homeostasis and suggest a mechanistic basis for genome instability resulting from deregulated DNA replication, observed in cancer and other disease states.
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Affiliation(s)
- Stephan Hamperl
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Michael J Bocek
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Joshua C Saldivar
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Tomek Swigut
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Karlene A Cimprich
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.
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Shima N, Pederson KD. Dormant origins as a built-in safeguard in eukaryotic DNA replication against genome instability and disease development. DNA Repair (Amst) 2017; 56:166-173. [PMID: 28641940 PMCID: PMC5547906 DOI: 10.1016/j.dnarep.2017.06.019] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
DNA replication is a prerequisite for cell proliferation, yet it can be increasingly challenging for a eukaryotic cell to faithfully duplicate its genome as its size and complexity expands. Dormant origins now emerge as a key component for cells to successfully accomplish such a demanding but essential task. In this perspective, we will first provide an overview of the fundamental processes eukaryotic cells have developed to regulate origin licensing and firing. With a special focus on mammalian systems, we will then highlight the role of dormant origins in preventing replication-associated genome instability and their functional interplay with proteins involved in the DNA damage repair response for tumor suppression. Lastly, deficiencies in the origin licensing machinery will be discussed in relation to their influence on stem cell maintenance and human diseases.
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Affiliation(s)
- Naoko Shima
- The University of Minnesota, Twin Cities, Department of Genetics, Cell Biology and Development, Masonic Cancer Center, 6-160 Jackson Hall, 321 Church St SE., Minneapolis, MN 55455, United States.
| | - Kayla D Pederson
- The University of Minnesota, Twin Cities, Department of Genetics, Cell Biology and Development, Masonic Cancer Center, 6-160 Jackson Hall, 321 Church St SE., Minneapolis, MN 55455, United States
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15
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Pruitt SC, Qin M, Wang J, Kunnev D, Freeland A. A Signature of Genomic Instability Resulting from Deficient Replication Licensing. PLoS Genet 2017; 13:e1006547. [PMID: 28045896 PMCID: PMC5242545 DOI: 10.1371/journal.pgen.1006547] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 01/18/2017] [Accepted: 12/19/2016] [Indexed: 11/23/2022] Open
Abstract
Insufficient licensing of DNA replication origins has been shown to result in genome instability, stem cell deficiency, and cancers. However, it is unclear whether the DNA damage resulting from deficient replication licensing occurs generally or if specific sites are preferentially affected. To map locations of ongoing DNA damage in vivo, the DNAs present in red blood cell micronuclei were sequenced. Many micronuclei are the product of DNA breaks that leave acentromeric remnants that failed to segregate during mitosis and should reflect the locations of breaks. To validate the approach we show that micronuclear sequences identify known common fragile sites under conditions that induce breaks at these locations (hydroxyurea). In MCM2 deficient mice a different set of preferred breakage sites is identified that includes the tumor suppressor gene Tcf3, which is known to contribute to T-lymphocytic leukemias that arise in these mice, and the 45S rRNA gene repeats. Many RBC micronuclei result from double strand DNA breaks that give rise to acentromeric chromosomal fragments that fail to incorporate into nuclei during mitosis and consequently remain in the cell following enucleation. Here, RBC micronuclear DNA is sequenced (Mic-Seq) to define the locations of breaks genome-wide and this assay is used to study ongoing genome instability resulting from insufficient DNA replication origin licensing. Using a mouse model, we show that there is increased instability at discrete sites across the genome, which include genes that are recurrently deleted in the T-lymphocytic leukemias that eventually arise in these mice. Mic-Seq may provide an effective means of predicting locations that are susceptible to genetic damage and these predictions may have prognostic value.
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Affiliation(s)
- Steven C. Pruitt
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, New York, United States of America
- * E-mail:
| | - Maochun Qin
- Department of Biostatistics and Bioinformatics, Roswell Park Cancer Institute, Buffalo, New York, United States of America
| | - Jianmin Wang
- Department of Biostatistics and Bioinformatics, Roswell Park Cancer Institute, Buffalo, New York, United States of America
| | - Dimiter Kunnev
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, New York, United States of America
| | - Amy Freeland
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, New York, United States of America
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Moriyama K, Lai MS, Masai H. Interaction of Rif1 Protein with G-Quadruplex in Control of Chromosome Transactions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1042:287-310. [PMID: 29357064 DOI: 10.1007/978-981-10-6955-0_14] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Recent studies on G-quadruplex (G4) revealed crucial and conserved functions of G4 in various biological systems. We recently showed that Rif1, a conserved nuclear factor, binds to G4 present in the intergenic regions and plays a major role in spatiotemporal regulation of DNA replication. Rif1 may tether chromatin fibers through binding to G4, generating specific chromatin domains that dictate the replication timing. G4 and its various binding partners are now implicated in many other chromosome regulations, including transcription, replication initiation, recombination, gene rearrangement, and transposition.
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Affiliation(s)
- Kenji Moriyama
- Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo, 156-8506, Japan
| | - Mong Sing Lai
- Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo, 156-8506, Japan
| | - Hisao Masai
- Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo, 156-8506, Japan.
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17
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Unreplicated DNA remaining from unperturbed S phases passes through mitosis for resolution in daughter cells. Proc Natl Acad Sci U S A 2016; 113:E5757-64. [PMID: 27516545 PMCID: PMC5047195 DOI: 10.1073/pnas.1603252113] [Citation(s) in RCA: 96] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
To prevent rereplication of genomic segments, the eukaryotic cell cycle is divided into two nonoverlapping phases. During late mitosis and G1 replication origins are "licensed" by loading MCM2-7 double hexamers and during S phase licensed replication origins activate to initiate bidirectional replication forks. Replication forks can stall irreversibly, and if two converging forks stall with no intervening licensed origin-a "double fork stall" (DFS)-replication cannot be completed by conventional means. We previously showed how the distribution of replication origins in yeasts promotes complete genome replication even in the presence of irreversible fork stalling. This analysis predicts that DFSs are rare in yeasts but highly likely in large mammalian genomes. Here we show that complementary strand synthesis in early mitosis, ultrafine anaphase bridges, and G1-specific p53-binding protein 1 (53BP1) nuclear bodies provide a mechanism for resolving unreplicated DNA at DFSs in human cells. When origin number was experimentally altered, the number of these structures closely agreed with theoretical predictions of DFSs. The 53BP1 is preferentially bound to larger replicons, where the probability of DFSs is higher. Loss of 53BP1 caused hypersensitivity to licensing inhibition when replication origins were removed. These results provide a striking convergence of experimental and theoretical evidence that unreplicated DNA can pass through mitosis for resolution in the following cell cycle.
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18
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Foulk MS, Urban JM, Casella C, Gerbi SA. Characterizing and controlling intrinsic biases of lambda exonuclease in nascent strand sequencing reveals phasing between nucleosomes and G-quadruplex motifs around a subset of human replication origins. Genome Res 2015; 25:725-35. [PMID: 25695952 PMCID: PMC4417120 DOI: 10.1101/gr.183848.114] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Accepted: 02/18/2015] [Indexed: 01/02/2023]
Abstract
Nascent strand sequencing (NS-seq) is used to discover DNA replication origins genome-wide, allowing identification of features for their specification. NS-seq depends on the ability of lambda exonuclease (λ-exo) to efficiently digest parental DNA while leaving RNA-primer protected nascent strands intact. We used genomics and biochemical approaches to determine if λ-exo digests all parental DNA sequences equally. We report that λ-exo does not efficiently digest G-quadruplex (G4) structures in a plasmid. Moreover, λ-exo digestion of nonreplicating genomic DNA (LexoG0) enriches GC-rich DNA and G4 motifs genome-wide. We used LexoG0 data to control for nascent strand–independent λ-exo biases in NS-seq and validated this approach at the rDNA locus. The λ-exo–controlled NS-seq peaks are not GC-rich, and only 35.5% overlap with 6.8% of all G4s, suggesting that G4s are not general determinants for origin specification but may play a role for a subset. Interestingly, we observed a periodic spacing of G4 motifs and nucleosomes around the peak summits, suggesting that G4s may position nucleosomes at this subset of origins. Finally, we demonstrate that use of Na+ instead of K+ in the λ-exo digestion buffer reduced the effect of G4s on λ-exo digestion and discuss ways to increase both the sensitivity and specificity of NS-seq.
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Affiliation(s)
- Michael S Foulk
- Brown University Division of Biology and Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Providence, Rhode Island 02912, USA
| | - John M Urban
- Brown University Division of Biology and Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Providence, Rhode Island 02912, USA
| | - Cinzia Casella
- Brown University Division of Biology and Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Providence, Rhode Island 02912, USA
| | - Susan A Gerbi
- Brown University Division of Biology and Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Providence, Rhode Island 02912, USA
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Kunnev D, Freeland A, Qin M, Wang J, Pruitt SC. Isolation and sequencing of active origins of DNA replication by nascent strand capture and release (NSCR). J Biol Methods 2015; 2. [PMID: 26949711 DOI: 10.14440/jbm.2015.92] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Nascent strand capture and release (NSCR) is a method for isolation of short nascent strands to identify origins of DNA replication. The protocol provided involves isolation of total DNA, denaturation, size fractionation on a sucrose gradient, 5'-biotinylation of the appropriate size nucleic acids, binding to a streptavidin coated magnetic beads, intensive washing, and specific release of only the RNA-containing chimeric nascent strand DNA using ribonuclease I (RNase I). The method has been applied to mammalian cells derived from proliferative tissues and cell culture but could be used for any system where DNA replication is primed by a small RNA resulting in chimeric RNA-DNA molecules.
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Affiliation(s)
- Dimiter Kunnev
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | - Amy Freeland
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | - Maochun Qin
- Department of Biostatistics and Bioinformatics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | - Jianmin Wang
- Department of Biostatistics and Bioinformatics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | - Steven C Pruitt
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
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