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Ouzon-Shubeita H, Barnes R, Schmaltz LF, Lee S. Structure of a DNA Glycosylase Bound to a Nicked T:G Mismatch-Containing DNA. Molecules 2025; 30:2083. [PMID: 40363888 PMCID: PMC12073362 DOI: 10.3390/molecules30092083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2025] [Revised: 04/30/2025] [Accepted: 05/02/2025] [Indexed: 05/15/2025] Open
Abstract
Mismatched T:G base pairs can arise during de novo replication as well as base excision repair (BER). In particular, the action of the gap-filling polymerase β (Polβ) can generate a T:G pair as well as a nick in the DNA backbone. The processing of a nicked T:G mispair is poorly understood. We are interested in understanding whether the T:G-specific DNA glycosylase MBD4 can recognize and process nicked T:G mismatches. We have discovered that MBD4 binds a nicked T:G-containing DNA, but does not cleave thymine opposite guanine. To gain insight into this, we have determined a crystal structure of human MBD4 bound to a nicked T:G-containing DNA. This structure displayed the full insertion of thymine into the catalytic site and the recognition of thymine based on the catalytic site's amino acid residues. However, thymine excision did not occur, presumably due to the inactivation of the catalytic D560 carboxylate nucleophile via a polar interaction with the 5'-hydrogen phosphate of the nicked DNA. The nicked complex was greatly stabilized by an ordered water molecule that formed four hydrogen bonds with the nicked DNA and MBD4. Interestingly, the arginine finger R468 did not engage in the phosphate pinching that is commonly observed in T:G mismatch recognition complex structures. Instead, the guanidinium moiety of R468 made bifurcated hydrogen bonding interactions with O6 of guanine, thereby stabilizing the estranged guanine. These observations suggest that R468 may sense and disrupt T:G pairs within the DNA duplex and stabilize the flipped-out thymine. The structure described here would be a close mimic of an intermediate in the base extrusion pathway induced by DNA glycosylase.
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Affiliation(s)
| | | | | | - Seongmin Lee
- The Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, The University of Texas at Austin, Austin, TX 78712, USA
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2
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Chang Y, Long M, Shan H, Liu L, Zhong S, Luo JL. Combining gut microbiota modulation and immunotherapy: A promising approach for treating microsatellite stable colorectal cancer. Crit Rev Oncol Hematol 2025; 208:104629. [PMID: 39864533 DOI: 10.1016/j.critrevonc.2025.104629] [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: 12/04/2024] [Revised: 01/20/2025] [Accepted: 01/21/2025] [Indexed: 01/28/2025] Open
Abstract
Colorectal cancer (CRC) is one of the most prevalent and lethal cancers worldwide, ranking third in incidence and second in mortality. While immunotherapy has shown promise in patients with deficient mismatch repair (dMMR) or high microsatellite instability (MSI-H), its effectiveness in proficient mismatch repair (pMMR) or microsatellite stable (MSS) CRC remains limited. Recent advances highlight the gut microbiota as a potential modulator of anti-tumor immunity. The gut microbiome can significantly influence the efficacy of immune checkpoint inhibitors (ICIs), especially in pMMR/MSS CRC, by modulating immune responses and systemic inflammation. This review explores the role of the gut microbiota in pMMR/MSS CRC, the mechanisms by which it may enhance immunotherapy, and current strategies for microbiota modulation. We discuss the potential benefits of combining microbiota-targeting interventions with immunotherapy to improve treatment outcomes for pMMR/MSS CRC patients.
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Affiliation(s)
- Yujie Chang
- The Cancer Research Institute and the Second Affiliated Hospital, Hengyang Medical School, University of South China (USC), Hunan 421001, China; MOE Key Lab of Rare Pediatric Diseases, Hengyang Medical School, USC, Hunan 421001, China
| | - Min Long
- The Cancer Research Institute and the Second Affiliated Hospital, Hengyang Medical School, University of South China (USC), Hunan 421001, China; MOE Key Lab of Rare Pediatric Diseases, Hengyang Medical School, USC, Hunan 421001, China
| | - Hanguo Shan
- The Cancer Research Institute and the Second Affiliated Hospital, Hengyang Medical School, University of South China (USC), Hunan 421001, China; Hunan Provincial Key Laboratory of Basic and Clinical Pharmacological Research of Gastrointestinal Cancer, USC, Hunan 421001, China
| | - Logen Liu
- Hunan Provincial Key Laboratory of Basic and Clinical Pharmacological Research of Gastrointestinal Cancer, USC, Hunan 421001, China
| | - Shangwei Zhong
- The Cancer Research Institute and the Second Affiliated Hospital, Hengyang Medical School, University of South China (USC), Hunan 421001, China; MOE Key Lab of Rare Pediatric Diseases, Hengyang Medical School, USC, Hunan 421001, China
| | - Jun-Li Luo
- The Cancer Research Institute and the Second Affiliated Hospital, Hengyang Medical School, University of South China (USC), Hunan 421001, China; Hunan Provincial Key Laboratory of Basic and Clinical Pharmacological Research of Gastrointestinal Cancer, USC, Hunan 421001, China; MOE Key Lab of Rare Pediatric Diseases, Hengyang Medical School, USC, Hunan 421001, China; National Health Commission Key Laboratory of Birth Defect Research and Prevention, Hunan Provincial Maternal and Child Health Care Hospital, USC, Hunan 410008, China.
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3
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Ma R, Li G, Ye Y, Liang L, Wang C, Zhou H, Zhang P, An L, Shi G, Chen Q, Xu H, Gao Z. Prognosis conferred by molecular features of appendix-derived Pseudomyxoma Peritonei. Transl Oncol 2025; 53:102279. [PMID: 39929063 DOI: 10.1016/j.tranon.2025.102279] [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: 10/30/2024] [Accepted: 01/05/2025] [Indexed: 03/01/2025] Open
Abstract
INTRODUCTION Pseudomyxoma Peritonei (PMP) is an extremely rare disease characterized by progressive accumulation of mucinous ascites and implants in the peritoneum. We investigated the prognostic value for response to cytoreductive surgery (CRS) or hyperthermic intraperitoneal chemotherapy (HIPEC) and dissected potential beneficial targeted therapy utilizing genomic characteristics. METHODS Whole-exome sequencing (WES) was performed on tissue specimens and matched white blood cells from 81 patients with PMP. The study investigated mutational signatures, profiling, and their correlation with progression-free survival (PFS) and overall survival (OS). RESULTS Signature 3 (HRD) and signature 15 (dMMR) were dominant. NMF cluster 1, characterized by signature 4, exhibited a worse prognosis. The p53 and TGF-β signaling pathways may contribute as risk factors for worse OS and PFS, respectively. MUC16-mutated patients had worse PFS (P = 0.016) and OS (P = 0.004) compared to wild-type patients. Patients with tumor mutational burden (TMB) > 1(P = 0.026) or alterations in TP53 (P = 0.006) or SMAD4 (P = 0.013) had significantly worse OS compared to those with a TMB < 1 or normal genes. Patients with homologous recombination deficiency (HRD) positivity (P = 0.003) or alterations in TGFBR2 (P = 0.037) experienced worse PFS compared to their respective control groups. Furthermore, NMF cluster1 (P = 0.020), TP53 (P = 0.004), and MUC16 (P = 0.013) were identified as independent prognostic factors for OS, while HRD status (P = 0.003) was independent predictors for PFS in PMP. CONCLUSIONS The study reveals that genomic profiling can serve as a robust tool for identifying prognostic markers in PMP. The identified genomic mutations and signaling pathway offer new avenues for targeted therapies.
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Affiliation(s)
- Ruiqing Ma
- Department of Gastroenterological Surgery, Peking University People's Hospital, Beijing, China; Department of Myxoma, Aerospace Center Hospital, Beijing, 100049, China.
| | - Guojun Li
- Thorgene Co., Ltd., Beijing, 100176, China.
| | - Yingjiang Ye
- Department of Gastroenterological Surgery, Peking University People's Hospital, Beijing, China.
| | - Lei Liang
- Department of Ultrasound, Aerospace Center Hospital, Beijing, China
| | - Chong Wang
- Department of Myxoma, Aerospace Center Hospital, Beijing, 100049, China
| | - Haipeng Zhou
- Department of Myxoma, Aerospace Center Hospital, Beijing, 100049, China
| | - Pu Zhang
- Department of Myxoma, Aerospace Center Hospital, Beijing, 100049, China
| | - Lubiao An
- Department of Myxoma, Aerospace Center Hospital, Beijing, 100049, China
| | - Guanjun Shi
- Department of Myxoma, Aerospace Center Hospital, Beijing, 100049, China
| | - Qian Chen
- Thorgene Co., Ltd., Beijing, 100176, China.
| | - Hongbin Xu
- Department of Myxoma, Aerospace Center Hospital, Beijing, 100049, China.
| | - Zhidong Gao
- Department of Gastroenterological Surgery, Peking University People's Hospital, Beijing, China.
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Zhang J, Wang G, Liu J, Tang F, Wang S, Li Y. ITGA4 as a potential prognostic and immunotherapeutic biomarker in human cancer and its clinical significance in gastric cancer: an integrated analysis and validation. Front Oncol 2025; 15:1513622. [PMID: 40012546 PMCID: PMC11860100 DOI: 10.3389/fonc.2025.1513622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2024] [Accepted: 01/27/2025] [Indexed: 02/28/2025] Open
Abstract
Background Integrin Subunit Alpha 4 (ITGA4), a member of the integrin protein family, is involved in the progression of malignant tumors. However, its role across different cancer types is not well understood. Methods Utilizing multi-omics data, we comprehensively evaluated ITGA4's expression, clinical relevance, diagnostic and prognostic value, functions, mutations, and methylation status, along with its impact on immunity, mismatch repair (MMR), heterogeneity, stemness, immunotherapy responsiveness, and drug resistance in pan-cancer, with partial validation in gastric cancer (GC) using transcriptomic analysis, single-cell data, western blot (WB), wound-healing assay, flow cytometry and immunohistochemistry (IHC). We further investigated its correlation with clinicopathology and serological markers on tissues from 80 GC patients. Results ITGA4 expression was generally low in normal tissues but varied significantly across tumor types, with higher levels in advanced stages and grades. It demonstrated diagnostic value in 20 cancer types and effectively predicted 1-, 3-, and 5-year survival rates as part of a prognostic model. ITGA4 played roles in cell adhesion, migration, immune regulation, and pathways like PI3K-Akt and TSC-mTOR. It showed alterations in 22 cancer types, with methylation at 9 sites inhibiting its expression. ITGA4 positively correlated with immune cell infiltration, immune regulatory genes, chemokines, and might reduce microsatellite instability (MSI) and tumor mutation burden (TMB) by promoting MMR gene expression. It could also predict immunotherapy efficacy and chemotherapy sensitivity. In GC, high ITGA4 expression was related to poor prognosis, promoted tumor proliferation and migration, and enhanced immune cell infiltration. ITGA4 expression was higher in GC cells and tissues than normal ones. Its downregulation inhibited GC cell migration and promoted apoptosis. Moreover, ITGA4 was correlated with N stage, pathological stage, neural and vascular invasion, serum levels of Ki-67, immune cells, CRP and CA125. Conclusion ITGA4 is a potential biomarker and therapeutic target to enhance cancer treatment and improve patient outcomes.
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Affiliation(s)
- Jiaxing Zhang
- The Second Hospital and Clinical Medical School, Lanzhou University, Lanzhou, China
- Digestive System Tumor Prevention and Treatment and Translational Medicine Engineering Innovation Center of Lanzhou University, Lanzhou University, Lanzhou, China
| | - Gang Wang
- School of Basic Medical Sciences of Lanzhou University, Lanzhou University, Lanzhou, China
| | - Jie Liu
- Ecosystem Change and Population Health Research Group, School of Public Health and Social Work, The Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, QLD, Australia
| | - Futian Tang
- Digestive System Tumor Prevention and Treatment and Translational Medicine Engineering Innovation Center of Lanzhou University, Lanzhou University, Lanzhou, China
| | - Song Wang
- The Second Hospital and Clinical Medical School, Lanzhou University, Lanzhou, China
| | - Yumin Li
- The Second Hospital and Clinical Medical School, Lanzhou University, Lanzhou, China
- Digestive System Tumor Prevention and Treatment and Translational Medicine Engineering Innovation Center of Lanzhou University, Lanzhou University, Lanzhou, China
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5
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Kuai L, Sun J, Peng Q, Zhao X, Yuan B, Liu S, Bi Y, Shi Y. Cryo-EM structure of DNA polymerase of African swine fever virus. Nucleic Acids Res 2024; 52:10717-10729. [PMID: 39189451 PMCID: PMC11417396 DOI: 10.1093/nar/gkae739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2024] [Revised: 08/07/2024] [Accepted: 08/19/2024] [Indexed: 08/28/2024] Open
Abstract
African swine fever virus (ASFV) is one of the most important causative agents of animal diseases and can cause highly fatal diseases in swine. ASFV DNA polymerase (DNAPol) is responsible for genome replication and highly conserved in all viral genotypes showing an ideal target for drug development. Here, we systematically determined the structures of ASFV DNAPol in apo, replicating and editing states. Structural analysis revealed that ASFV DNAPol had a classical right-handed structure and showed the highest similarity to the structure of human polymerase delta. Intriguingly, ASFV DNAPol has a much longer fingers subdomain, and the thumb and palm subdomain form a unique interaction that has never been seen. Mutagenesis work revealed that the loss of this unique interaction decreased the enzymatic activity. We also found that the β-hairpin of ASFV DNAPol is located below the template strand in the editing state, which is different from the editing structures of other known B family DNAPols with the β-hairpin above the template strand. It suggests that B family DNAPols have evolved two ways to facilitate the dsDNA unwinding during the transition from replicating into editing state. These findings figured out the working mechanism of ASFV DNAPol and will provide a critical structural basis for the development of antiviral drugs.
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Affiliation(s)
- Lu Kuai
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
- Medical School, University of Chinese Academy of Sciences, Beijing 100049, China
- Beijing Life Science Academy, Beijing 102209, China
| | - Junqing Sun
- College of Veterinary Medicine, Shanxi Agricultural University, Jinzhong, 030801, China
| | - Qi Peng
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
- Beijing Life Science Academy, Beijing 102209, China
| | - Xuejin Zhao
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
- Beijing Life Science Academy, Beijing 102209, China
| | - Bin Yuan
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Sheng Liu
- Shenzhen Children's Hospital, Shenzhen 518038, China
| | - Yuhai Bi
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
- Medical School, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yi Shi
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
- Medical School, University of Chinese Academy of Sciences, Beijing 100049, China
- Beijing Life Science Academy, Beijing 102209, China
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6
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Averill JR, Lin JC, Jung J, Jung H. Novel insights into the role of translesion synthesis polymerase in DNA incorporation and bypass of 5-fluorouracil in colorectal cancer. Nucleic Acids Res 2024; 52:4295-4312. [PMID: 38416579 PMCID: PMC11077093 DOI: 10.1093/nar/gkae102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2023] [Revised: 01/12/2024] [Accepted: 02/01/2024] [Indexed: 03/01/2024] Open
Abstract
5-Fluorouracil (5-FU) is the first-line chemotherapeutic agent in colorectal cancer, and resistance to 5-FU easily emerges. One of the mechanisms of drug action and resistance of 5-FU is through DNA incorporation. Our quantitative reverse-transcription PCR data showed that one of the translesion synthesis (TLS) DNA polymerases, DNA polymerase η (polη), was upregulated within 72 h upon 5-FU administration at 1 and 10 μM, indicating that polη is one of the first responding polymerases, and the only TLS polymerase, upon the 5-FU treatment to incorporate 5-FU into DNA. Our kinetic studies revealed that 5-fluoro-2'-deoxyuridine triphosphate (5FdUTP) was incorporated across dA 41 and 28 times more efficiently than across dG and across inosine, respectively, by polη indicating that the mutagenicity of 5-FU incorporation is higher in the presence of inosine and that DNA lesions could lead to more mutagenic incorporation of 5-FU. Our polη crystal structures complexed with DNA and 5FdUTP revealed that dA:5FdUTP base pair is like dA:dTTP in the active site of polη, while 5FdUTP adopted 4-enol tautomer in the base pairs with dG and HX increasing the insertion efficiency compared to dG:dTTP for the incorrect insertions. These studies confirm that polη engages in the DNA incorporation and bypass of 5-FU.
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Affiliation(s)
- Jameson R Averill
- Division of Medicinal Chemistry, School of Pharmacy, University of Connecticut, Storrs, CT 06269, USA
| | - Jackson C Lin
- Division of Medicinal Chemistry, School of Pharmacy, University of Connecticut, Storrs, CT 06269, USA
| | - John Jung
- Division of Medicinal Chemistry, School of Pharmacy, University of Connecticut, Storrs, CT 06269, USA
| | - Hunmin Jung
- Division of Medicinal Chemistry, School of Pharmacy, University of Connecticut, Storrs, CT 06269, USA
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Liu S, Li W, Chen J, Li M, Geng Y, Liu Y, Wu W. The footprint of gut microbiota in gallbladder cancer: a mechanistic review. Front Cell Infect Microbiol 2024; 14:1374238. [PMID: 38774627 PMCID: PMC11106419 DOI: 10.3389/fcimb.2024.1374238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2024] [Accepted: 04/22/2024] [Indexed: 05/24/2024] Open
Abstract
Gallbladder cancer (GBC) is the most common malignant tumor of the biliary system with the worst prognosis. Even after radical surgery, the majority of patients with GBC have difficulty achieving a clinical cure. The risk of tumor recurrence remains more than 65%, and the overall 5-year survival rate is less than 5%. The gut microbiota refers to a variety of microorganisms living in the human intestine, including bacteria, viruses and fungi, which profoundly affect the host state of general health, disease and even cancer. Over the past few decades, substantial evidence has supported that gut microbiota plays a critical role in promoting the progression of GBC. In this review, we summarize the functions, molecular mechanisms and recent advances of the intestinal microbiota in GBC. We focus on the driving role of bacteria in pivotal pathways, such as virulence factors, metabolites derived from intestinal bacteria, chronic inflammatory responses and ecological niche remodeling. Additionally, we emphasize the high level of correlation between viruses and fungi, especially EBV and Candida spp., with GBC. In general, this review not only provides a solid theoretical basis for the close relationship between gut microbiota and GBC but also highlights more potential research directions for further research in the future.
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Affiliation(s)
- Shujie Liu
- Joint Program of Nanchang University and Queen Mary University of London, Jiangxi Medical College of Nanchang University, Nanchang, Jiangxi, China
| | - Weijian Li
- Department of Biliary-Pancreatic Surgery, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Biliary Tract Disease Research, Shanghai, China
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Research Center of Biliary Tract Disease, Shanghai, China
| | - Jun Chen
- Department of Biliary-Pancreatic Surgery, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Biliary Tract Disease Research, Shanghai, China
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Research Center of Biliary Tract Disease, Shanghai, China
| | - Maolan Li
- Department of Biliary-Pancreatic Surgery, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Biliary Tract Disease Research, Shanghai, China
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Research Center of Biliary Tract Disease, Shanghai, China
| | - Yajun Geng
- Department of Biliary-Pancreatic Surgery, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Biliary Tract Disease Research, Shanghai, China
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Research Center of Biliary Tract Disease, Shanghai, China
| | - Yingbin Liu
- Department of Biliary-Pancreatic Surgery, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Biliary Tract Disease Research, Shanghai, China
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Research Center of Biliary Tract Disease, Shanghai, China
| | - Wenguang Wu
- Department of Biliary-Pancreatic Surgery, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Biliary Tract Disease Research, Shanghai, China
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Research Center of Biliary Tract Disease, Shanghai, China
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8
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Jiang YK, Medley EA, Brown GW. Two independent DNA repair pathways cause mutagenesis in template switching deficient Saccharomyces cerevisiae. Genetics 2023; 225:iyad153. [PMID: 37594077 DOI: 10.1093/genetics/iyad153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 08/08/2023] [Indexed: 08/19/2023] Open
Abstract
Upon DNA replication stress, cells utilize the postreplication repair pathway to repair single-stranded DNA and maintain genome integrity. Postreplication repair is divided into 2 branches: error-prone translesion synthesis, signaled by proliferating cell nuclear antigen (PCNA) monoubiquitination, and error-free template switching, signaled by PCNA polyubiquitination. In Saccharomyces cerevisiae, Rad5 is involved in both branches of repair during DNA replication stress. When the PCNA polyubiquitination function of Rad5 s disrupted, Rad5 recruits translesion synthesis polymerases to stalled replication forks, resulting in mutagenic repair. Details of how mutagenic repair is carried out, as well as the relationship between Rad5-mediated mutagenic repair and the canonical PCNA-mediated mutagenic repair, remain to be understood. We find that Rad5-mediated mutagenic repair requires the translesion synthesis polymerase ζ but does not require other yeast translesion polymerase activities. Furthermore, we show that Rad5-mediated mutagenic repair is independent of PCNA binding by Rev1 and so is separable from canonical mutagenic repair. In the absence of error-free template switching, both modes of mutagenic repair contribute additively to replication stress response in a replication timing-independent manner. Cellular contexts where error-free template switching is compromised are not simply laboratory phenomena, as we find that a natural variant in RAD5 is defective in PCNA polyubiquitination and therefore defective in error-free repair, resulting in Rad5- and PCNA-mediated mutagenic repair. Our results highlight the importance of Rad5 in regulating spontaneous mutagenesis and genetic diversity in S. cerevisiae through different modes of postreplication repair.
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Affiliation(s)
- Yangyang Kate Jiang
- Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, ON M5S 1A8, Canada
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON M5S 3E1, Canada
| | - Eleanor A Medley
- Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, ON M5S 1A8, Canada
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON M5S 3E1, Canada
| | - Grant W Brown
- Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, ON M5S 1A8, Canada
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON M5S 3E1, Canada
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9
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Andrés CMC, de la Lastra JMP, Juan CA, Plou FJ, Pérez-Lebeña E. Chemical Insights into Oxidative and Nitrative Modifications of DNA. Int J Mol Sci 2023; 24:15240. [PMID: 37894920 PMCID: PMC10607741 DOI: 10.3390/ijms242015240] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 10/09/2023] [Accepted: 10/13/2023] [Indexed: 10/29/2023] Open
Abstract
This review focuses on DNA damage caused by a variety of oxidizing, alkylating, and nitrating species, and it may play an important role in the pathophysiology of inflammation, cancer, and degenerative diseases. Infection and chronic inflammation have been recognized as important factors in carcinogenesis. Under inflammatory conditions, reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from inflammatory and epithelial cells, and result in the formation of oxidative and nitrative DNA lesions, such as 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-nitroguanine. Cellular DNA is continuously exposed to a very high level of genotoxic stress caused by physical, chemical, and biological agents, with an estimated 10,000 modifications occurring every hour in the genetic material of each of our cells. This review highlights recent developments in the chemical biology and toxicology of 2'-deoxyribose oxidation products in DNA.
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Affiliation(s)
| | - José Manuel Pérez de la Lastra
- Institute of Natural Products and Agrobiology, CSIC-Spanish Research Council, Avda. AstrofísicoFco. Sánchez, 3, 38206 La Laguna, Spain
| | - Celia Andrés Juan
- Cinquima Institute and Department of Organic Chemistry, Faculty of Sciences, Valladolid University, Paseo de Belén, 7, 47011 Valladolid, Spain;
| | - Francisco J. Plou
- Institute of Catalysis and Petrochemistry, CSIC-Spanish Research Council, 28049 Madrid, Spain;
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10
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Gong Q, Dong Q, Zhong B, Zhang T, Cao D, Zhang Y, Ma D, Cai X, Li Z. Clinicopathological features, prognostic significance, and associated tumor cell functions of family with sequence similarity 111 member B in pancreatic adenocarcinoma. J Clin Lab Anal 2022; 36:e24784. [DOI: 10.1002/jcla.24784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Revised: 10/31/2022] [Accepted: 11/12/2022] [Indexed: 11/22/2022] Open
Affiliation(s)
- Qi Gong
- Wuhan University of Science and Technology School of Medicine Wuhan China
| | - QingTai Dong
- The First School of Clinical Medicine Southern Medical University Guangzhou China
| | - Bin Zhong
- The First School of Clinical Medicine Southern Medical University Guangzhou China
| | - Tao Zhang
- Wuhan University of Science and Technology School of Medicine Wuhan China
| | - Ding Cao
- Department of General Surgery General Hospital of Central Theatre Command Wuhan China
| | - Yi Zhang
- Department of General Surgery General Hospital of Central Theatre Command Wuhan China
| | - Dandan Ma
- Department of General Surgery General Hospital of Central Theatre Command Wuhan China
| | - Xun Cai
- Department of General Surgery General Hospital of Central Theatre Command Wuhan China
| | - ZhongHu Li
- Department of General Surgery General Hospital of Central Theatre Command Wuhan China
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11
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Luo Y, Rao Y, Gu X, Chai P, Yang Y, Lin J, Xu X, Jia R, Xu S. Novel MSH6 mutation predicted metastasis in eyelid and periocular squamous cell carcinoma. J Eur Acad Dermatol Venereol 2022; 36:2331-2342. [PMID: 35855666 DOI: 10.1111/jdv.18454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Accepted: 06/03/2022] [Indexed: 11/28/2022]
Abstract
BACKGROUND Our previous research revealed the relative local aggressiveness of eyelid and periocular squamous cell carcinoma (EPSCC), but its distinct genetic characteristics involved remain unknown. OBJECTIVES We conducted this study based on next-generation sequencing to identify the genetic distinctiveness of EPSCC and damaging mutations for possible etiology and poor prognosis. METHODS We performed sequencing using a 556-gene panel (smartonco) in 48 EPSCCs. Cox hazards model was applied to explore mutated genes that increase risk of metastasis and death. Pathogenesis of the mutations was predicted by sequence alignment algorithms. RESULTS The most commonly mutated genes were KMT2C (N=17, 35%), LRP1B (N=14, 29%), KMT2D (N=12, 25%), PTCH1(N=10, 21%) and TP53(N=10, 21%). DNA mismatch repair (MMR) genes (42%) like MSH6(19%) and MLH3(12%) were among the most frequently mutated genes. Cell cycle regulators including TP53(21%) and CDKN2A (10%) were less frequently mutated than in other squamous cell carcinomas (SCCs). Ultra violet exposure, MMR deficiency and aging were the main etiology. Of note, KMT2C has a deleterious mutation hotspot. Patients burdened with MSH6 mutation has a higher risk of overall metastasis (P=0.045, HR=5.165) and nodal metastasis (P=0.022, HR=14.038). Moreover, a hotspot mutation MSH6E52A brought an even higher risk of nodal metastasis (P=0.011, HR=18.745). CONCLUSIONS EPSCCs displayed a unique mutation profile from cutaneous SCCs and mucosal SCCs. We have identified novel damaging mutations in epigenetic regulators like KMT2C boosted early onset of EPSCCs in addition to UVR, aging or MMR deficiency. And malfunction of MMR genes worsened prognosis.
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Affiliation(s)
- Y Luo
- Department of Ophthalmology, Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai, China
| | - Y Rao
- Department of pathology, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China
| | - X Gu
- Department of Ophthalmology, Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai, China
| | - P Chai
- Department of Ophthalmology, Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai, China
| | - Y Yang
- Department of Ophthalmology, Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai, China
| | - J Lin
- Department of pathology, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China
| | - X Xu
- Department of Ophthalmology, Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai, China
| | - R Jia
- Department of Ophthalmology, Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai, China
| | - S Xu
- Department of Ophthalmology, Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai, China
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12
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Tang Q, Gulkis M, McKenna R, Çağlayan M. Structures of LIG1 that engage with mutagenic mismatches inserted by polβ in base excision repair. Nat Commun 2022; 13:3860. [PMID: 35790757 PMCID: PMC9256674 DOI: 10.1038/s41467-022-31585-w] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 06/23/2022] [Indexed: 11/09/2022] Open
Abstract
DNA ligase I (LIG1) catalyzes the ligation of the nick repair intermediate after gap filling by DNA polymerase (pol) β during downstream steps of the base excision repair (BER) pathway. However, how LIG1 discriminates against the mutagenic 3'-mismatches incorporated by polβ at atomic resolution remains undefined. Here, we determine the X-ray structures of LIG1/nick DNA complexes with G:T and A:C mismatches and uncover the ligase strategies that favor or deter the ligation of base substitution errors. Our structures reveal that the LIG1 active site can accommodate a G:T mismatch in the wobble conformation, where an adenylate (AMP) is transferred to the 5'-phosphate of a nick (DNA-AMP), while it stays in the LIG1-AMP intermediate during the initial step of the ligation reaction in the presence of an A:C mismatch at the 3'-strand. Moreover, we show mutagenic ligation and aberrant nick sealing of dG:T and dA:C mismatches, respectively. Finally, we demonstrate that AP-endonuclease 1 (APE1), as a compensatory proofreading enzyme, removes the mismatched bases and interacts with LIG1 at the final BER steps. Our overall findings provide the features of accurate versus mutagenic outcomes coordinated by a multiprotein complex including polβ, LIG1, and APE1 to maintain efficient repair.
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Affiliation(s)
- Qun Tang
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL, 32610, USA
| | - Mitchell Gulkis
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL, 32610, USA
| | - Robert McKenna
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL, 32610, USA
| | - Melike Çağlayan
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL, 32610, USA.
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13
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Lamb NA, Bard JE, Loll-Krippleber R, Brown GW, Surtees JA. Complex mutation profiles in mismatch repair and ribonucleotide reductase mutants reveal novel repair substrate specificity of MutS homolog (MSH) complexes. Genetics 2022; 221:6605222. [PMID: 35686905 PMCID: PMC9339293 DOI: 10.1093/genetics/iyac092] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Accepted: 05/24/2022] [Indexed: 12/30/2022] Open
Abstract
Determining mutation signatures is standard for understanding the etiology of human tumors and informing cancer treatment. Multiple determinants of DNA replication fidelity prevent mutagenesis that leads to carcinogenesis, including the regulation of free deoxyribonucleoside triphosphate pools by ribonucleotide reductase and repair of replication errors by the mismatch repair system. We identified genetic interactions between rnr1 alleles that skew and/or elevate deoxyribonucleoside triphosphate levels and mismatch repair gene deletions. These defects indicate that the rnr1 alleles lead to increased mutation loads that are normally acted upon by mismatch repair. We then utilized a targeted deep-sequencing approach to determine mutational profiles associated with mismatch repair pathway defects. By combining rnr1 and msh mutations to alter and/or increase deoxyribonucleoside triphosphate levels and alter the mutational load, we uncovered previously unreported specificities of Msh2-Msh3 and Msh2-Msh6. Msh2-Msh3 is uniquely able to direct the repair of G/C single-base deletions in GC runs, while Msh2-Msh6 specifically directs the repair of substitutions that occur at G/C dinucleotides. We also identified broader sequence contexts that influence variant profiles in different genetic backgrounds. Finally, we observed that the mutation profiles in double mutants were not necessarily an additive relationship of mutation profiles in single mutants. Our results have implications for interpreting mutation signatures from human tumors, particularly when mismatch repair is defective.
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Affiliation(s)
- Natalie A Lamb
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14203, USA
| | - Jonathan E Bard
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14203, USA,University at Buffalo Genomics and Bioinformatics Core, State University of New York at Buffalo, Buffalo, NY 14203, USA
| | - Raphael Loll-Krippleber
- Department of Biochemistry and Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Grant W Brown
- Department of Biochemistry and Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Jennifer A Surtees
- Corresponding author: Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Rm 4215, 955 Main Street, Buffalo, NY 14203, USA.
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14
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Wang Y, Imran A, Shami A, Chaudhary AA, Khan S. Decipher the Helicobacter pylori Protein Targeting in the Nucleus of Host Cell and their Implications in Gallbladder Cancer: An insilico approach. J Cancer 2021; 12:7214-7222. [PMID: 34729122 PMCID: PMC8558644 DOI: 10.7150/jca.63517] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 10/03/2021] [Indexed: 12/26/2022] Open
Abstract
Gallbladder cancer (GBC) is one of the leading causes of cancer-related mortality worldwide. Researchers have investigated that specific strains of bacteria are connected with growth of different types of cancers in human. Some reports show possible implication of Helicobacter pylori (H. pylori) in the etiology of gallbladder cancer (GBC). Their enigmatic mechanisms, nevertheless, are not still well clear. We sought to predict whether various proteins of H. pylori targeted to nucleus of host cells and their implication in growth of gallbladder cancer. GBC is one of the leading causes of cancer mortality worldwide. We applied bioinformatics approach to analyze the H. pylori proteins targeting into the nucleus of host cells using different bioinformatics predictors including nuclear localization signal (NLS) mapper Balanced Subcellular Localization (BaCelLo) and Hum-mPLoc 2.0. Various nuclear targeting proteins may have a potential role in GBC etiology during intracellular infection. We identified 46 H. pylori proteins targeted into nucleus of host cell through bioinformatics tools. These H. pylori nucleus-targeting proteins might alter the normal function of host cells by disturbing the different pathways including replication, transcription, translation etc. Various nucleus-targeted proteins can affect the normal growth and development of infected cells. We propose that H. pylori proteins targeting into the nucleus of host cells regulate GBC growth using different strategies. These integrative bioinformatics research demonstrated several H. pylori proteins that may serve as possible targets or biomarkers for early cure and treatment or diagnosis GBC.
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Affiliation(s)
- Yunjian Wang
- Department of Hepatobiliary and Pancreatic Surgery, The Affiliated Tumor Hospital of Zhengzhou University, Zhengzhou City, Henan Province, 450008, China
| | - Ahamad Imran
- King Abdullah Institute for Nanotechnology, King Saud University, Riyadh 11451, Saudi Arabia
| | - Ashwag Shami
- Department of Biology, College of Sciences, Princess Nourah bint Abdulrahman University, Riyadh 11617, Saudi Arabia
| | - Anis Ahmad Chaudhary
- Department of Biology, College of Science, Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh 11623, Saudi Arabia
| | - Shahanavaj Khan
- Department of Health Sciences, Novel Global Community Educational Foundation, Australia.,Department of Bioscience, Shri Ram Group of College (SRGC), Muzaffarnagar, UP, India.,Department of Pharmaceutics, College of Pharmacy, PO Box 2457, King Saud University, Riyadh 11451, Saudi Arabia
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15
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Balzerano A, Paccosi E, Proietti-De-Santis L. Evolutionary Mechanisms of Cancer Suggest Rational Therapeutic Approaches. Cytogenet Genome Res 2021; 161:362-371. [PMID: 34461614 DOI: 10.1159/000516530] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 03/25/2021] [Indexed: 11/19/2022] Open
Abstract
The goal in personalized therapeutic approaches for cancer medicine is to identify specific mutations with prognostic and therapeutic value in order to tailor the therapy for the single patient. The most powerful obstacle for personalized medicine arises from intratumor heterogeneity and clonal evolution, which can promote drug resistance. In this scenario, new technologies, such as next-generation sequencing, have emerged as a central diagnostic tool to profile cancer (epi)genomic landscapes. Therefore, a better understanding of the biological mechanisms underlying cancer evolution is mandatory and represents the current challenge to accurately predict whether cancer will recur after chemotherapy with the aim to tailor rational therapeutic approaches.
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Affiliation(s)
- Alessio Balzerano
- Unit of Molecular Genetics of Aging, Department of Ecology and Biology, University of Tuscia, Viterbo, Italy
| | - Elena Paccosi
- Unit of Molecular Genetics of Aging, Department of Ecology and Biology, University of Tuscia, Viterbo, Italy
| | - Luca Proietti-De-Santis
- Unit of Molecular Genetics of Aging, Department of Ecology and Biology, University of Tuscia, Viterbo, Italy
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16
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Nachtergael A, Lanterbecq D, Spanoghe M, Belayew A, Duez P. Effects of Chemopreventive Natural Compounds on the Accuracy of 8-oxo-7,8-dihydro-2'-deoxyguanosine Translesion Synthesis. PLANTA MEDICA 2021; 87:868-878. [PMID: 34237787 DOI: 10.1055/a-1527-1435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Translesion synthesis is a DNA damage tolerance mechanism that relies on a series of specialized DNA polymerases able to bypass a lesion on a DNA template strand during replication or post-repair synthesis. Specialized translesion synthesis DNA polymerases pursue replication by inserting a base opposite to this lesion, correctly or incorrectly depending on the lesion nature, involved DNA polymerase(s), sequence context, and still unknown factors. To measure the correct or mutagenic outcome of 8-oxo-7,8-dihydro-2'-deoxyguanosine bypass by translesion synthesis, a primer-extension assay was performed in vitro on a template DNA bearing this lesion in the presence of nuclear proteins extracted from human intestinal epithelial cells (FHs 74 Int cell line); the reaction products were analyzed by both denaturing capillary electrophoresis (to measure the yield of translesion elongation) and pyrosequencing (to determine the identity of the nucleotide inserted in front of the lesion). The influence of 14 natural polyphenols on the correct or mutagenic outcome of translesion synthesis through 8-oxo-7,8-dihydro-2'-deoxyguanosine was then evaluated in 2 experimental conditions by adding the polyphenol either (i) to the reaction mix during the primer extension assay; or (ii) to the culture medium, 24 h before cell harvest and nuclear proteins extraction. Most of the tested polyphenols significantly influenced the outcome of translesion synthesis, either through an error-free (apigenin, baicalein, sakuranetin, and myricetin) or a mutagenic pathway (epicatechin, chalcone, genistein, magnolol, and honokiol).
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Affiliation(s)
- Amandine Nachtergael
- Unit of Therapeutic Chemistry and Pharmacognosy, Research Institute for Health Sciences and Technology, University of Mons (UMONS), Mons, Belgium
| | - Déborah Lanterbecq
- Laboratory of Biotechnology and Applied Biology, Haute Ecole Provinciale de Hainaut CONDORCET, Ath, Belgium
| | - Martin Spanoghe
- Laboratory of Biotechnology and Applied Biology, Haute Ecole Provinciale de Hainaut CONDORCET, Ath, Belgium
| | - Alexandra Belayew
- Department of Metabolic and Molecular Biochemistry, Research Institute for Health Sciences and Technology, University of Mons (UMONS), Mons, Belgium
| | - Pierre Duez
- Unit of Therapeutic Chemistry and Pharmacognosy, Research Institute for Health Sciences and Technology, University of Mons (UMONS), Mons, Belgium
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17
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Insights into the substrate discrimination mechanisms of methyl-CpG-binding domain 4. Biochem J 2021; 478:1985-1997. [PMID: 33960375 DOI: 10.1042/bcj20210017] [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: 01/15/2021] [Revised: 05/05/2021] [Accepted: 05/07/2021] [Indexed: 11/17/2022]
Abstract
G:T mismatches, the major mispairs generated during DNA metabolism, are repaired in part by mismatch-specific DNA glycosylases such as methyl-CpG-binding domain 4 (MBD4) and thymine DNA glycosylase (TDG). Mismatch-specific DNA glycosylases must discriminate the mismatches against million-fold excess correct base pairs. MBD4 efficiently removes thymine opposite guanine but not opposite adenine. Previous studies have revealed that the substrate thymine is flipped out and enters the catalytic site of the enzyme, while the estranged guanine is stabilized by Arg468 of MBD4. To gain further insights into the mismatch discrimination mechanism of MBD4, we assessed the glycosylase activity of MBD4 toward various base pairs. In addition, we determined a crystal structure of MBD4 bound to T:O6-methylguanine-containing DNA, which suggests the O6 and N2 of purine and the O4 of pyrimidine are required to be a substrate for MBD4. To understand the role of the Arg468 finger in catalysis, we evaluated the glycosylase activity of MBD4 mutants, which revealed the guanidinium moiety of Arg468 may play an important role in catalysis. D560N/R468K MBD4 bound to T:G mismatched DNA shows that the side chain amine moiety of the Lys stabilizes the flipped-out thymine by a water-mediated phosphate pinching, while the backbone carbonyl oxygen of the Lys engages in hydrogen bonds with N2 of the estranged guanine. Comparison of various DNA glycosylase structures implies the guanidinium and amine moieties of Arg and Lys, respectively, may involve in discriminating between substrate mismatches and nonsubstrate base pairs.
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18
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Marima R, Hull R, Penny C, Dlamini Z. Mitotic syndicates Aurora Kinase B (AURKB) and mitotic arrest deficient 2 like 2 (MAD2L2) in cohorts of DNA damage response (DDR) and tumorigenesis. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2021; 787:108376. [PMID: 34083040 DOI: 10.1016/j.mrrev.2021.108376] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 03/05/2021] [Accepted: 04/20/2021] [Indexed: 12/31/2022]
Abstract
Aurora Kinase B (AURKB) and Mitotic Arrest Deficient 2 Like 2 (MAD2L2) are emerging anticancer therapeutic targets. AURKB and MAD2L2 are the least well studied members of their protein families, compared to AURKA and MAD2L1. Both AURKB and MAD2L2 play a critical role in mitosis, cell cycle checkpoint, DNA damage response (DDR) and normal physiological processes. However, the oncogenic roles of AURKB and MAD2L2 in tumorigenesis and genomic instability have also been reported. DDR acts as an arbitrator for cell fate by either repairing the damage or directing the cell to self-destruction. While there is strong evidence of interphase DDR, evidence of mitotic DDR is just emerging and remains largely unelucidated. To date, inhibitors of the DDR components show effective anti-cancer roles. Contrarily, long-term resistance towards drugs that target only one DDR target is becoming a challenge. Targeting interactions between protein-protein or protein-DNA holds prominent therapeutic potential. Both AURKB and MAD2L2 play critical roles in the success of mitosis and their emerging roles in mitotic DDR cannot be ignored. Small molecule inhibitors for AURKB are in clinical trials. A few lead compounds towards MAD2L2 inhibition have been discovered. Targeting mitotic DDR components and their interaction is emerging as a potent next generation anti-cancer therapeutic target. This can be done by developing small molecule inhibitors for AURKB and MAD2L2, thereby targeting DDR components as anti-cancer therapeutic targets and/or targeting mitotic DDR. This review focuses on AURKB and MAD2L2 prospective synergy to deregulate the p53 DDR pathway and promote favourable conditions for uncontrolled cell proliferation.
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Affiliation(s)
- Rahaba Marima
- SA-MRC/UP Precision Prevention and Novel Drug Targets for HIV-Associated Cancers Extramural Unit, Pan African Cancer Research Institute, Faculty of Health Sciences, University of Pretoria, Hatfield, 0028, South Africa.
| | - Rodney Hull
- SA-MRC/UP Precision Prevention and Novel Drug Targets for HIV-Associated Cancers Extramural Unit, Pan African Cancer Research Institute, Faculty of Health Sciences, University of Pretoria, Hatfield, 0028, South Africa
| | - Clement Penny
- Department of Internal Medicine, School of Clinical Medicine, Faculty of Health Sciences, University of the Witwatersrand, Parktown, 2193, South Africa
| | - Zodwa Dlamini
- SA-MRC/UP Precision Prevention and Novel Drug Targets for HIV-Associated Cancers Extramural Unit, Pan African Cancer Research Institute, Faculty of Health Sciences, University of Pretoria, Hatfield, 0028, South Africa
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19
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Belyeu JR, Brand H, Wang H, Zhao X, Pedersen BS, Feusier J, Gupta M, Nicholas TJ, Brown J, Baird L, Devlin B, Sanders SJ, Jorde LB, Talkowski ME, Quinlan AR. De novo structural mutation rates and gamete-of-origin biases revealed through genome sequencing of 2,396 families. Am J Hum Genet 2021; 108:597-607. [PMID: 33675682 PMCID: PMC8059337 DOI: 10.1016/j.ajhg.2021.02.012] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 02/12/2021] [Indexed: 01/05/2023] Open
Abstract
Each human genome includes de novo mutations that arose during gametogenesis. While these germline mutations represent a fundamental source of new genetic diversity, they can also create deleterious alleles that impact fitness. Whereas the rate and patterns of point mutations in the human germline are now well understood, far less is known about the frequency and features that impact de novo structural variants (dnSVs). We report a family-based study of germline mutations among 9,599 human genomes from 33 multigenerational CEPH-Utah families and 2,384 families from the Simons Foundation Autism Research Initiative. We find that de novo structural mutations detected by alignment-based, short-read WGS occur at an overall rate of at least 0.160 events per genome in unaffected individuals, and we observe a significantly higher rate (0.206 per genome) in ASD-affected individuals. In both probands and unaffected samples, nearly 73% of de novo structural mutations arose in paternal gametes, and we predict most de novo structural mutations to be caused by mutational mechanisms that do not require sequence homology. After multiple testing correction, we did not observe a statistically significant correlation between parental age and the rate of de novo structural variation in offspring. These results highlight that a spectrum of mutational mechanisms contribute to germline structural mutations and that these mechanisms most likely have markedly different rates and selective pressures than those leading to point mutations.
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Affiliation(s)
- Jonathan R Belyeu
- Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA
| | - Harrison Brand
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA; Program in Medical and Population Genetics and Stanley Center for Psychiatric Research, Broad Institute of Harvard and MIT, Cambridge, MA 02114, USA
| | - Harold Wang
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA; Program in Medical and Population Genetics and Stanley Center for Psychiatric Research, Broad Institute of Harvard and MIT, Cambridge, MA 02114, USA
| | - Xuefang Zhao
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA; Program in Medical and Population Genetics and Stanley Center for Psychiatric Research, Broad Institute of Harvard and MIT, Cambridge, MA 02114, USA
| | - Brent S Pedersen
- Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA
| | - Julie Feusier
- Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112, USA
| | - Meenal Gupta
- Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA
| | - Thomas J Nicholas
- Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA
| | - Joseph Brown
- Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA
| | - Lisa Baird
- Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA
| | - Bernie Devlin
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Stephan J Sanders
- Department of Psychiatry, UCSF Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA 94143, USA; Institute for Human Genetics, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Lynn B Jorde
- Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA; Utah Center for Genetic Discovery, University of Utah, Salt Lake City, UT 84112, USA
| | - Michael E Talkowski
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA; Program in Medical and Population Genetics and Stanley Center for Psychiatric Research, Broad Institute of Harvard and MIT, Cambridge, MA 02114, USA.
| | - Aaron R Quinlan
- Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA; Department of Biomedical Informatics, University of Utah, Salt Lake City, UT 84112, USA; Utah Center for Genetic Discovery, University of Utah, Salt Lake City, UT 84112, USA.
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20
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Zhou Z, Xie X, Wang X, Zhang X, Li W, Sun T, Cai Y, Wu J, Dang C, Zhang H. Correlations Between Tumor Mutation Burden and Immunocyte Infiltration and Their Prognostic Value in Colon Cancer. Front Genet 2021; 12:623424. [PMID: 33664769 PMCID: PMC7921807 DOI: 10.3389/fgene.2021.623424] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 01/21/2021] [Indexed: 12/12/2022] Open
Abstract
Background Colon cancer has a huge incidence and mortality worldwide every year. Immunotherapy could be a new therapeutic option for patients with advanced colon cancer. Tumor mutation burden (TMB) and immune infiltration are considered critical in immunotherapy but their characteristics in colon cancer are still controversial. Methods The somatic mutation, transcriptome, and clinical data of patients with colon cancer were obtained from the TCGA database. Patients were divided into low or high TMB groups using the median TMB value. Somatic mutation landscape, differentially expressed genes, and immune-related hub genes, Gene Ontology and KEGG, gene set enrichment, and immune infiltration analyses were investigated between the two TMB groups. Univariate and multivariate Cox analyses were utilized to construct a prognostic gene signature. The differences in immune infiltration, and the expression of HLA-related genes and checkpoint genes were investigated between the two immunity groups based on single sample gene set enrichment analysis. Finally, a nomogram of the prognostic prediction model integrating TMB, immune infiltration, and clinical parameters was established. Calibration plots and receiver operating characteristic curves (ROC) were drawn, and the C-index was calculated to assess the predictive ability. Results Missense mutations and single nucleotide polymorphisms were the major variant characteristics in colon cancer. The TMB level showed significant differences in N stage, M stage, pathological stage, and immune infiltration. CD8+ T cells, activated memory CD4+ T cells, activated NK cells, and M1 macrophages infiltrated more in the high-TMB group. The antigen processing and presentation signaling pathway was enriched in the high-TMB group. Two immune related genes (CHGB and SCT) were identified to be correlated with colon cancer survival (HR = 1.39, P = 0.01; HR = 1.26, P = 0.02, respectively). Notably, the expression of SCT was identified as a risk factor in the immune risk model, in which high risk patients showed poorer survival (P = 0.04). High immunity status exhibited significant correlations with immune response pathways, HLA-related genes, and immune checkpoint genes. Finally, including nine factors, our nomogram prediction model showed better calibration (C-index = 0.764) and had an AUC of 0.737. Conclusion In this study, we investigated the patterns and prognostic roles of TMB and immune infiltration in colon cancer, which provided new insights into the tumor microenvironment and immunotherapies and the development of a novel nomogram prognostic prediction model for patients with colon cancer.
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Affiliation(s)
- Zhangjian Zhou
- Department of Oncology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Xin Xie
- Department of Surgical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Xuan Wang
- Department of Surgical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Xin Zhang
- Department of Surgical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Wenxin Li
- Department of Surgical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Tuanhe Sun
- Department of Surgical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Yifan Cai
- Department of Oncology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Jianhua Wu
- Department of Oncology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Chengxue Dang
- Department of Surgical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Hao Zhang
- Department of Surgical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
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Monakhova MV, Milakina MA, Trikin RM, Oretskaya TS, Kubareva EA. Functional Specifics of the MutL Protein of the DNA Mismatch Repair System in Different Organisms. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2020. [DOI: 10.1134/s1068162020060217] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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22
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Catalytic mechanism of the mismatch-specific DNA glycosylase methyl-CpG-binding domain 4. Biochem J 2020; 477:1601-1612. [PMID: 32297632 DOI: 10.1042/bcj20200125] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 04/09/2020] [Accepted: 04/14/2020] [Indexed: 12/15/2022]
Abstract
Thymine:guanine base pairs are major promutagenic mismatches occurring in DNA metabolism. If left unrepaired, these mispairs can cause C to T transition mutations. In humans, T:G mismatches are repaired in part by mismatch-specific DNA glycosylases such as methyl-CpG-binding domain 4 (hMBD4) and thymine-DNA glycosylase. Unlike lesion-specific DNA glycosylases, T:G-mismatch-specific DNA glycosylases specifically recognize both bases of the mismatch and remove the thymine but only from mispairs with guanine. Despite the advances in biochemical and structural characterizations of hMBD4, the catalytic mechanism of hMBD4 remains elusive. Herein, we report two structures of hMBD4 processing T:G-mismatched DNA. A high-resolution crystal structure of Asp560Asn hMBD4-T:G complex suggests that hMBD4-mediated glycosidic bond cleavage occurs via a general base catalysis mechanism assisted by Asp560. A structure of wild-type hMBD4 encountering T:G-containing DNA shows the generation of an apurinic/apyrimidinic (AP) site bearing the C1'-(S)-OH. The inversion of the stereochemistry at the C1' of the AP-site indicates that a nucleophilic water molecule approaches from the back of the thymine substrate, suggesting a bimolecular displacement mechanism (SN2) for hMBD4-catalyzed thymine excision. The AP-site is stabilized by an extensive hydrogen bond network in the MBD4 catalytic site, highlighting the role of MBD4 in protecting the genotoxic AP-site.
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Huyghe N, Baldin P, Van den Eynde M. Immunotherapy with immune checkpoint inhibitors in colorectal cancer: what is the future beyond deficient mismatch-repair tumours? Gastroenterol Rep (Oxf) 2020; 8:11-24. [PMID: 32104582 PMCID: PMC7034232 DOI: 10.1093/gastro/goz061] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 09/25/2019] [Accepted: 10/22/2019] [Indexed: 12/17/2022] Open
Abstract
Following initial success in melanoma and lung tumours, immune checkpoint inhibitors (ICIs) are now well recognized as a major immunotherapy treatment modality for multiple types of solid cancers. In colorectal cancer (CRC), the small subset that is mismatch-repair-deficient and microsatellite-instability-high (dMMR/MSI-H) derive benefit from immunotherapy; however, the vast majority of patients with proficient MMR (pMMR) or with microsatellite stable (MSS) CRC do not. Immunoscore and the consensus molecular subtype classifications are promising biomarkers in predicting therapeutic efficacy in selected CRC. In pMRR/MSS CRC, biomarkers are also needed to understand the molecular mechanisms governing immune reactivity and to predict their relationship to treatment. The continuous development of such biomarkers would offer new perspectives and more personalized treatments by targeting oncological options, including ICIs, which modify the tumour-immune microenvironment. In this review, we focus on CRC and discuss the current status of ICIs, the role of biomarkers to predict response to immunotherapy, and the approaches being explored to render pMMR/MSS CRC more immunogenic through the use of combined therapies.
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Affiliation(s)
- Nicolas Huyghe
- Institut de Recherche Clinique et Expérimentale (Pole MIRO), UCLouvain, Brussels, Belgium
| | - Paméla Baldin
- Department of Pathology, Cliniques Universitaires St-Luc, Institut Roi Albert II, Brussels, Belgium
| | - Marc Van den Eynde
- Institut de Recherche Clinique et Expérimentale (Pole MIRO), UCLouvain, Brussels, Belgium
- Department of Medical Oncology, Cliniques Universitaires St-Luc, Institut Roi Albert II, Brussels, Belgium
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24
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Williams GM, Petrides AK, Balakrishnan L, Surtees JA. Tracking Expansions of Stable and Threshold Length Trinucleotide Repeat Tracts In Vivo and In Vitro Using Saccharomyces cerevisiae. Methods Mol Biol 2020; 2056:25-68. [PMID: 31586340 DOI: 10.1007/978-1-4939-9784-8_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] [Indexed: 06/10/2023]
Abstract
Trinucleotide repeat (TNR) tracts are inherently unstable during DNA replication, leading to repeat expansions and/or contractions. Expanded tracts are the cause of over 40 neurodegenerative and neuromuscular diseases. In this chapter, we focus on the (CAG)n and (CTG)n repeat sequences that, when expanded, lead to Huntington's disease (HD) and myotonic dystrophy type 1 (DM1), respectively, as well as a number of other neurodegenerative diseases. TNR tracts in most individuals are relatively small and stable in terms of length. However, TNR tracts become increasingly prone to expansion as tract length increases, eventually leading to very long tracts that disrupt coding (e.g. HD) or noncoding (e.g., DM1) regions of the genome. It is important to understand the early stages in TNR expansions, that is, the transition from small, stable lengths to susceptible threshold lengths. We describe PCR-based in vivo assays, using the model system Saccharomyces cerevisiae, to determine and characterize the dynamic behavior of TNR tracts in the stable and threshold ranges. We also describe a simple in vitro system to assess tract dynamics during 5' single-stranded DNA (ssDNA) flap processing and to assess the role of different DNA metabolism proteins in these dynamics. These assays can ultimately be used to determine factors that influence the early stages of TNR tract expansion.
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Affiliation(s)
- Gregory M Williams
- Centre for Chromosome Biology, National University of Ireland, Galway, Galway, Ireland
- Galway Neuroscience Centre, National Universityof Ireland, Galway, Galway, Ireland
| | | | - Lata Balakrishnan
- Department of Biology, Indiana University Purdue University Indianapolis, Indianapolis, IN, USA
| | - Jennifer A Surtees
- Department of Biochemistry, JacobsSchool of Medicine and BiomedicalSciences, State University of New York atBuffalo, Buffalo, NY, USA.
- Genetics, Genomics and Bioinformatics Program, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, USA.
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25
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Mardis ER. Neoantigens and genome instability: impact on immunogenomic phenotypes and immunotherapy response. Genome Med 2019; 11:71. [PMID: 31747945 PMCID: PMC6865009 DOI: 10.1186/s13073-019-0684-0] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 11/05/2019] [Indexed: 12/13/2022] Open
Abstract
The resurgence of immune therapies in cancer medicine has elicited a corresponding interest in understanding the basis of patient response or resistance to these treatments. One aspect of patient response clearly lies in the genomic alterations that are associated with cancer onset and progression, including those that contribute to genomic instability and the resulting creation of novel peptide sequences that may present as neoantigens. The immune reaction to these unique ‘non-self’ peptides is frequently suppressed by the tumor itself, but the use of checkpoint blockade therapies, personalized vaccines, or a combination of these treatments may elicit a tumor-specific immune response that results in cell death. Massively parallel sequencing, coupled with different computational analyses, provides unbiased identification of the germline and somatic alterations that drive cancer development, and of those alterations that lead to neoantigens. These range from simple point mutations that change single amino acids to complex alterations, such as frameshift insertion or deletion mutations, splice-site alterations that lead to exon skipping, structural alterations that lead to the formation of fusion proteins, and other forms of collateral damage caused by genome instability that result in new protein sequences unique to the cancer. The various genome instability phenotypes can be identified as alterations that impact DNA replication or mismatch repair pathways or by their genomic signatures. This review provides an overview of current knowledge regarding the fundamentals of genome replication and of both germline and somatic alterations that disrupt normal replication, leading to various forms of genomic instability in cancers, to the resulting generation of neoantigens and, ultimately, to immune-responsive and resistant phenotypes.
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Affiliation(s)
- Elaine R Mardis
- Institute for Genomic Medicine at Nationwide Children's Hospital, The Ohio State University College of Medicine, Children's Drive, Colombus, OH, 43205, USA.
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26
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27
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Abstract
Primordial germ cells (PGCs) must complete a complex and dynamic developmental program during embryogenesis to establish the germline. This process is highly conserved and involves a diverse array of tasks required of PGCs, including migration, survival, sex differentiation, and extensive epigenetic reprogramming. A common theme across many organisms is that PGC success is heterogeneous: only a portion of all PGCs complete all these steps while many other PGCs are eliminated from further germline contribution. The differences that distinguish successful PGCs as a population are not well understood. Here, we examine variation that exists in PGCs as they navigate the many stages of this developmental journey. We explore potential sources of PGC heterogeneity and their potential implications in affecting germ cell behaviors. Lastly, we discuss the potential for PGC development to function as a multistage selection process that assesses heterogeneity in PGCs to refine germline quality.
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Affiliation(s)
- Daniel H Nguyen
- Department of Obstetrics, Gynecology and Reproductive Science, Center for Reproductive Sciences, Eli and Edythe Broad Center for Regeneration Medicine and Stem Cell Research, University of California, San Francisco, CA, United States
| | - Rebecca G Jaszczak
- Department of Obstetrics, Gynecology and Reproductive Science, Center for Reproductive Sciences, Eli and Edythe Broad Center for Regeneration Medicine and Stem Cell Research, University of California, San Francisco, CA, United States
| | - Diana J Laird
- Department of Obstetrics, Gynecology and Reproductive Science, Center for Reproductive Sciences, Eli and Edythe Broad Center for Regeneration Medicine and Stem Cell Research, University of California, San Francisco, CA, United States.
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28
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Ohno M. Spontaneous de novo germline mutations in humans and mice: rates, spectra, causes and consequences. Genes Genet Syst 2019; 94:13-22. [DOI: 10.1266/ggs.18-00015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Affiliation(s)
- Mizuki Ohno
- Department of Medical Biophysics and Radiation Biology, Faculty of Medical Science, Kyushu University
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29
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Hendriks LE, Rouleau E, Besse B. Clinical utility of tumor mutational burden in patients with non-small cell lung cancer treated with immunotherapy. Transl Lung Cancer Res 2018; 7:647-660. [PMID: 30505709 PMCID: PMC6249615 DOI: 10.21037/tlcr.2018.09.22] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 09/25/2018] [Indexed: 12/14/2022]
Abstract
Anti-programmed death (ligand)-1 [anti-PD-(L)1] therapies such as pembrolizumab, nivolumab or atezolizumab have become standard of care for non-small cell lung cancer (NSCLC) patients either in first line or beyond. PD-L1 expression level allows enriching the treated population with responders, but it is still not an optimal biomarker. Even in patients with PD-L1 tumor proportion score (TPS) levels of ≥50% treated with first line pembrolizumab overall response rate (ORR) is only 44.8% and overall survival at one year is 70%. Moreover, in combination trials with chemotherapy and anti-PD-(L)1 therapy, a significant proportion of patients does not respond (ORR ranges from 45.3% to 64.0%), regardless of PD-L1 expression. Furthermore, PD-L1 expression level is not associated with improved benefit in patients treated with combinations of anti-PD-(L)1 and anti-cytotoxic T-lymphocyte-associated antigen (anti-CTLA4) therapy. One of the new promising biomarkers is tumor mutational burden (TMB). It has been discovered that especially tumor types with a known high mutation rate such as NSCLC and melanoma respond best to immune checkpoint inhibitors (ICIs). An explanation is that this high mutation rate makes it more likely that neoantigens arise that are targeted by activated immune cells, but it is not feasible to determine neoantigen load in daily practice. However, TMB of a certain tumor type is associated with neoantigen load and outcome on ICIs. In this comprehensive review, we discuss the TMB analysis methods, the rationale to use TMB as a predictive biomarker and the clinical utility of TMB in NSCLC patients treated with ICIs.
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Affiliation(s)
- Lizza E. Hendriks
- Department of Cancer Medicine, Gustave Roussy, Institut d’Oncologie Thoracique (IOT), Gustave Roussy, Villejuif, France
- Department of Pulmonary Diseases, GROW - School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Etienne Rouleau
- Department of Medical Biology and Pathology, Gustave Roussy, Cancer Genetics Laboratory, Gustave Roussy, Villejuif, France
| | - Benjamin Besse
- Department of Cancer Medicine, Gustave Roussy, Institut d’Oncologie Thoracique (IOT), Gustave Roussy, Villejuif, France
- Paris-Sud University, Orsay, France
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30
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Fedeles BI, Essigmann JM. Impact of DNA lesion repair, replication and formation on the mutational spectra of environmental carcinogens: Aflatoxin B 1 as a case study. DNA Repair (Amst) 2018; 71:12-22. [PMID: 30309820 DOI: 10.1016/j.dnarep.2018.08.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
In a multicellular organism, somatic mutations represent a permanent record of the past chemical and biochemical perturbations experienced by a cell in its local microenvironment. Akin to a perpetual recording device, with every replication, genomic DNA accumulates mutations in patterns that reflect: i) the sequence context-dependent formation of DNA damage, due to environmental or endogenous reactive species, including spontaneous processes; ii) the activity of DNA repair pathways, which, depending on the type of lesion, can erase, ignore or exacerbate the mutagenic consequences of that DNA damage; and iii) the choice of replication machinery that synthesizes the nascent genomic copy. These three factors result in a richly contoured sequence context-dependent mutational spectrum that, from appearances, is distinct for most individual forms of DNA damage. Such a mutagenic legacy, if appropriately decoded, can reveal the local history of genome-altering events such as chemical or pathogen exposures, metabolic stress, and inflammation, which in turn can provide an indication of the underlying causes and mechanisms of genetic disease. Modern tools have positioned us to develop a deep mechanistic understanding of the cellular factors and pathways that modulate a mutational process and, in turn, provide opportunities for better diagnostic and prognostic biomarkers, better exposure risk assessment and even actionable therapeutic targets. The goal of this Perspective is to present a bottom-up, lesion-centric framework of mutagenesis that integrates the contributions of lesion replication, lesion repair and lesion formation to explain the complex mutational spectra that emerge in the genome following exposure to mutagens. The mutational spectra of the well-studied hepatocarcinogen aflatoxin B1 are showcased here as specific examples, but the implications are meant to be generalizable.
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Affiliation(s)
- Bogdan I Fedeles
- Departments of Biological Engineering, Chemistry and The Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
| | - John M Essigmann
- Departments of Biological Engineering, Chemistry and The Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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31
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Szwajczak E, Fijalkowska IJ, Suski C. The importance of an interaction network for proper DNA polymerase ζ heterotetramer activity. Curr Genet 2018; 64:575-580. [PMID: 29189894 PMCID: PMC5948306 DOI: 10.1007/s00294-017-0789-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 11/23/2017] [Accepted: 11/27/2017] [Indexed: 12/22/2022]
Abstract
Precisely controlled mechanisms have been evolved to rescue impeded DNA replication resulting from encountered obstacles and involve a set of low-fidelity translesion synthesis (TLS) DNA polymerases. Studies in recent years have brought new insights into those TLS polymerases, especially concerning the structure and subunit composition of DNA polymerase zeta (Pol ζ). Pol ζ is predominantly involved in induced mutagenesis as well as the bypass of noncanonical DNA structures, and it is proficient in extending from terminal mismatched nucleotides incorporated by major replicative DNA polymerases. Two active forms of Pol ζ, heterodimeric (Pol ζ2) and heterotetrameric (Pol ζ4) ones, have been identified and studied. Here, in the light of recent publications regarding induced and spontaneous mutagenesis and diverse interactions within Pol ζ holoenzyme, combined with Pol ζ binding to the TLS polymerase Rev1p, we discuss the subunit composition of Pol ζ in various cellular physiological conditions. Available data show that it is the heterotetrameric form of Pol ζ that is involved both during spontaneous and induced mutagenesis, and underline the importance of interactions within Pol ζ when an increased Pol ζ recruitment occurs. Understanding Pol ζ function in the bypass of DNA obstacles would give a significant insight into cellular tolerance of DNA damage, genetic instability and the onset of cancer progression.
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Affiliation(s)
- Ewa Szwajczak
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106, Warszawa, Poland
| | - Iwona J Fijalkowska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106, Warszawa, Poland
| | - Catherine Suski
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106, Warszawa, Poland.
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32
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Abstract
Microsatellite instability (MSI) refers to the hypermutator phenotype secondary to frequent polymorphism in short repetitive DNA sequences and single nucleotide substitution, as consequence of DNA mismatch repair (MMR) deficiency. MSI secondary to germline mutation in DNA MMR proteins is the molecular fingerprint of Lynch syndrome (LS), while epigenetic inactivation of these genes is more commonly found in sporadic MSI tumors. MSI occurs at different frequencies across malignancies, although original methods to assess MSI or MMR deficiency have been developed mostly in LS related cancers. Here we will discuss the current methods to detect MSI/MMR deficiency with a focus of new tools which are emerging as highly sensitive detector for MSI across multiple tumor types. Due to high frequencies of non-synonymous mutations, the presence of frameshift-mutated neoantigens, which can trigger a more robust and long-lasting immune response and strong TIL infiltration with tumor eradication, MSI has emerged as an important predictor of sensitivity for immunotherapy-based strategies, as showed by the recent FDA's first histology agnostic-accelerated approval to immune checkpoint inhibitors for refractory, adult and pediatric, MMR deficient (dMMR) or MSI high (MSI-H) tumors. Moreover, it is known that MSI status may predict cancer response/resistance to certain chemotherapies. Here we will describe the complex interplay between the genetic and clinical-pathological features of MSI/dMMR tumors and the cancer immunotherapy, with a focus on the predictive and prognostic role of MMR status for immune checkpoint inhibitors (ICIs) and providing some suggestions on how to conceive better predictive markers for immunotherapy in the next future.
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Affiliation(s)
- Marina Baretti
- The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins Hospital, United States
| | - Dung T Le
- The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins Hospital, United States.
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33
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López-Lázaro M. Cancer etiology: Variation in cancer risk among tissues is poorly explained by the number of gene mutations. Genes Chromosomes Cancer 2018; 57:281-293. [PMID: 29377495 DOI: 10.1002/gcc.22530] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 01/24/2018] [Accepted: 01/25/2018] [Indexed: 12/24/2022] Open
Abstract
Recent evidence indicates that the risk of being diagnosed with cancer in a tissue is strongly correlated (0.80) with the number of stem cell divisions accumulated by the tissue. Since cell division can generate random mutations during DNA replication, this correlation has been used to propose that cancer is largely caused by the accumulation of unavoidable mutations in driver genes. However, no correlation between the number of gene mutations and cancer risk across tissues has been reported. Because many somatic mutations in cancers originate prior to tumor initiation and the number of cell divisions occurring during tumor growth is similar among tissues, I use whole genome sequencing information from 22 086 cancer samples and incidence data from the largest cancer registry in each continent to study the relationship between the number of gene mutations and the risk of cancer across 33 tissue types. Results show a weak positive correlation (mean = 0.14) between these 2 parameters in each of the 5 cancer registries. The correlation became stronger (mean = 0.50) when gender-related cancers were excluded. Results also show that 1003 samples from 29 cancer types have zero mutations in genes. These data suggest that cancer etiology can be better explained by the accumulation of stem cell divisions than by the accumulation of gene mutations. Possible mechanisms by which the accumulation of cell divisions in stem cells increases the risk of cancer are discussed.
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Affiliation(s)
- Miguel López-Lázaro
- Department of Pharmacology, Faculty of Pharmacy, University of Seville, Spain
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34
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Williams GM, Surtees JA. Measuring Dynamic Behavior of Trinucleotide Repeat Tracts In Vivo in Saccharomyces cerevisiae. Methods Mol Biol 2018; 1672:439-470. [PMID: 29043641 DOI: 10.1007/978-1-4939-7306-4_30] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Trinucleotide repeat (TNR) tracts are inherently unstable during DNA replication, leading to repeat expansions and/or contractions. Expanded tracts are the cause of over 40 neurodegenerative and neuromuscular diseases. In this chapter, we focus on the (CNG)n repeat sequences that, when expanded, lead to Huntington's disease (HD), myotonic dystrophy type 1 (DM1), and a number of other neurodegenerative diseases. We describe a series of in vivo assays, using the model system Saccharomyces cerevisiae, to determine and characterize the dynamic behavior of TNR tracts that are in the early stages of expansion, i.e., the so-called threshold range. Through a series of time courses and PCR-based assays, dynamic changes in tract length can be observed as a function of time. These assays can ultimately be used to determine how genetic factors influence the process of tract expansion in these early stages.
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Affiliation(s)
- Gregory M Williams
- Department of Biochemistry, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, 14214, USA
| | - Jennifer A Surtees
- Department of Biochemistry, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, 14214, USA. .,Genetics, Genomics and Bioinformatics Program, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, 14214, USA.
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35
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Lada AG, Stepchenkova EI, Zhuk AS, Kliver SF, Rogozin IB, Polev DE, Dhar A, Pavlov YI. Recombination Is Responsible for the Increased Recovery of Drug-Resistant Mutants with Hypermutated Genomes in Resting Yeast Diploids Expressing APOBEC Deaminases. Front Genet 2017; 8:202. [PMID: 29312434 PMCID: PMC5733079 DOI: 10.3389/fgene.2017.00202] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2017] [Accepted: 11/22/2017] [Indexed: 12/11/2022] Open
Abstract
DNA editing deaminases (APOBECs) are implicated in generation of mutations in somatic cells during tumorigenesis. APOBEC-dependent mutagenesis is thought to occur during transient exposure of unprotected single-stranded DNA. Mutations frequently occur in clusters (kataegis). We investigated mechanisms of mutant generation in growing and resting diploid yeast expressing APOBEC from sea lamprey, PmCDA1, whose kataegistic effect was previously shown to be associated with transcription. We have found that the frequency of canavanine-resistant mutants kept raising after growth cessation, while the profile of transcription remained unchanged. Surprisingly, the overall number of mutations in the genomes did not elevate in resting cells. Thus, mutations were accumulated during vigorous growth stage with both intense replication and transcription. We found that the elevated recovery of can1 mutant clones in non-growing cells is the result of loss of heterozygosity (LOH) leading to clusters of homozygous mutations in the chromosomal regions distal to the reporter gene. We confirmed that recombination frequency in resting cells was elevated by orders of magnitude, suggesting that cells were transiently committed to meiotic levels of recombination, a process referred to in yeast genetics as return-to-growth. In its extreme, on day 6 of starvation, a few mutant clones were haploid, likely resulting from completed meiosis. Distribution of mutations along chromosomes indicated that PmCDA1 was active during ongoing recombination events and sometimes produced characteristic kataegis near initial breakpoints. AID and APOBEC1 behaved similar to PmCDA1. We conclude that replication, transcription, and mitotic recombination contribute to the recovered APOBEC-induced mutations in resting diploids. The mechanism is relevant to the initial stages of oncogenic transformation in terminally differentiated cells, when recombination may lead to the LOH exposing recessive mutations induced by APOBECs in cell's history and to acquisition of new mutations near original break.
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Affiliation(s)
- Artem G Lada
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, United States.,Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, CA, United States
| | - Elena I Stepchenkova
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, United States.,Department of Genetics and Biotechnology, Saint Petersburg State University, Saint Petersburg, Russia.,Vavilov Institute of General Genetics, Russian Academy of Sciences, Saint Petersburg, Russia
| | - Anna S Zhuk
- Department of Genetics and Biotechnology, Saint Petersburg State University, Saint Petersburg, Russia.,Vavilov Institute of General Genetics, Russian Academy of Sciences, Saint Petersburg, Russia
| | - Sergei F Kliver
- Department of Genetics and Biotechnology, Saint Petersburg State University, Saint Petersburg, Russia
| | - Igor B Rogozin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, United States.,Institute of Cytology and Genetics, Novosibirsk, Russia
| | - Dmitrii E Polev
- Research Resource Center "Biobank", Research Park, Saint-Petersburg State University, Saint Petersburg, Russia
| | - Alok Dhar
- Department of Genetics, Cell Biology and Anatomy and Vice Chancellor of Research Core, University of Nebraska Medical Center, Omaha, NE, United States
| | - Youri I Pavlov
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, United States.,Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, United States.,Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE, United States.,Department of Genetics Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE, United States
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36
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Sobinoff AP, Pickett HA. Alternative Lengthening of Telomeres: DNA Repair Pathways Converge. Trends Genet 2017; 33:921-932. [DOI: 10.1016/j.tig.2017.09.003] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2017] [Revised: 08/30/2017] [Accepted: 09/08/2017] [Indexed: 02/08/2023]
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37
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Garcia-Exposito L, Bournique E, Bergoglio V, Bose A, Barroso-Gonzalez J, Zhang S, Roncaioli JL, Lee M, Wallace CT, Watkins SC, Opresko PL, Hoffmann JS, O'Sullivan RJ. Proteomic Profiling Reveals a Specific Role for Translesion DNA Polymerase η in the Alternative Lengthening of Telomeres. Cell Rep 2017; 17:1858-1871. [PMID: 27829156 PMCID: PMC5406014 DOI: 10.1016/j.celrep.2016.10.048] [Citation(s) in RCA: 112] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2016] [Revised: 09/18/2016] [Accepted: 10/14/2016] [Indexed: 11/22/2022] Open
Abstract
Cancer cells rely on the activation of telomerase or the alternative lengthening of telomeres (ALT) pathways for telomere maintenance and survival. ALT involves homologous recombination (HR)-dependent exchange and/or HR-associated synthesis of telomeric DNA. Utilizing proximity-dependent biotinylation (BioID), we sought to determine the proteome of telomeres in cancer cells that employ these distinct telomere elongation mechanisms. Our analysis reveals that multiple DNA repair networks converge at ALT telomeres. These include the specialized translesion DNA synthesis (TLS) proteins FANCJ-RAD18-PCNA and, most notably, DNA polymerase eta (Polη). We observe that the depletion of Polη leads to increased ALT activity and late DNA polymerase δ (Polδ)-dependent synthesis of telomeric DNA in mitosis. We propose that Polη fulfills an important role in managing replicative stress at ALT telomeres, maintaining telomere recombination at tolerable levels and stimulating DNA synthesis by Polδ.
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Affiliation(s)
- Laura Garcia-Exposito
- Department of Pharmacology and Chemical Biology, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Elodie Bournique
- CRCT, Université de Toulouse, Inserm, CNRS, UPS Equipe Labellisée Ligue Contre le Cancer, Laboratoire d'Excellence Toulouse Cancer, 2 Avenue Hubert Curien, 31037 Toulouse, France
| | - Valérie Bergoglio
- CRCT, Université de Toulouse, Inserm, CNRS, UPS Equipe Labellisée Ligue Contre le Cancer, Laboratoire d'Excellence Toulouse Cancer, 2 Avenue Hubert Curien, 31037 Toulouse, France
| | - Arindam Bose
- Department of Environmental and Occupational Health, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Jonathan Barroso-Gonzalez
- Department of Pharmacology and Chemical Biology, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Sufang Zhang
- Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595, USA
| | - Justin L Roncaioli
- Department of Pharmacology and Chemical Biology, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Marietta Lee
- Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595, USA
| | - Callen T Wallace
- Department of Cell Biology, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Simon C Watkins
- Department of Cell Biology, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Patricia L Opresko
- Department of Environmental and Occupational Health, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Jean-Sébastien Hoffmann
- CRCT, Université de Toulouse, Inserm, CNRS, UPS Equipe Labellisée Ligue Contre le Cancer, Laboratoire d'Excellence Toulouse Cancer, 2 Avenue Hubert Curien, 31037 Toulouse, France
| | - Roderick J O'Sullivan
- Department of Pharmacology and Chemical Biology, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA.
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Paschalis V, Le Chatelier E, Green M, Nouri H, Képès F, Soultanas P, Janniere L. Interactions of the Bacillus subtilis DnaE polymerase with replisomal proteins modulate its activity and fidelity. Open Biol 2017; 7:170146. [PMID: 28878042 PMCID: PMC5627055 DOI: 10.1098/rsob.170146] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 08/01/2017] [Indexed: 01/09/2023] Open
Abstract
During Bacillus subtilis replication two replicative polymerases function at the replisome to collectively carry out genome replication. In a reconstituted in vitro replication assay, PolC is the main polymerase while the lagging strand DnaE polymerase briefly extends RNA primers synthesized by the primase DnaG prior to handing-off DNA synthesis to PolC. Here, we show in vivo that (i) the polymerase activity of DnaE is essential for both the initiation and elongation stages of DNA replication, (ii) its error rate varies inversely with PolC concentration, and (iii) its misincorporations are corrected by the mismatch repair system post-replication. We also found that the error rates in cells encoding mutator forms of both PolC and DnaE are significantly higher (up to 15-fold) than in PolC mutants. In vitro, we showed that (i) the polymerase activity of DnaE is considerably stimulated by DnaN, SSB and PolC, (ii) its error-prone activity is strongly inhibited by DnaN, and (iii) its errors are proofread by the 3' > 5' exonuclease activity of PolC in a stable template-DnaE-PolC complex. Collectively our data show that protein-protein interactions within the replisome modulate the activity and fidelity of DnaE, and confirm the prominent role of DnaE during B. subtilis replication.
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Affiliation(s)
- Vasileios Paschalis
- Centre for Biomolecular Sciences, School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Emmanuelle Le Chatelier
- Institut National de la Recherche Agronomique, Génétique Microbienne, 78350 Jouy-en-Josas, France
| | - Matthew Green
- Centre for Biomolecular Sciences, School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Hamid Nouri
- iSSB, Genopole, CNRS, Univ EVRY, Université Paris-Saclay, Génopole Campus 1, Genavenir 6, 5 rue Henri Desbruères, 91030 Evry, France
| | - François Képès
- iSSB, Genopole, CNRS, Univ EVRY, Université Paris-Saclay, Génopole Campus 1, Genavenir 6, 5 rue Henri Desbruères, 91030 Evry, France
| | - Panos Soultanas
- Centre for Biomolecular Sciences, School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Laurent Janniere
- iSSB, Genopole, CNRS, Univ EVRY, Université Paris-Saclay, Génopole Campus 1, Genavenir 6, 5 rue Henri Desbruères, 91030 Evry, France
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Hypermutated tumours in the era of immunotherapy: The paradigm of personalised medicine. Eur J Cancer 2017; 84:290-303. [PMID: 28846956 DOI: 10.1016/j.ejca.2017.07.026] [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] [Received: 07/14/2017] [Accepted: 07/19/2017] [Indexed: 12/13/2022]
Abstract
Immune checkpoint inhibitors have demonstrated unprecedented clinical activity in a wide range of cancers. Significant therapeutic responses have recently been observed in patients presenting mismatch repair-deficient (MMRD) tumours. MMRD cancers exhibit a remarkably high rate of mutations, which can result in the formation of neoantigens, hypothesised to enhance the antitumour immune response. In addition to MMRD tumours, cancers mutated in the exonuclease domain of the catalytic subunit of the DNA polymerase epsilon (POLE) also exhibit an ultramutated genome and are thus likely to benefit from immunotherapy. In this review, we provide an overview of recent data on hypermutated tumours, including MMRD and POLE-mutated cancers, with a focus on their distinctive clinicopathological and molecular characteristics as well as their immune environment. We also discuss the emergence of immune therapy to treat these hypermutated cancers, and we comment on the recent Food and Drug Administration approval of an immune checkpoint inhibitor, the programmed cell death 1 antibody (pembrolizumab, Keytruda), for the treatment of patients with metastatic MMRD cancers regardless of the tumour type. This breakthrough represents a turning point in the management of these hypermutated tumours and paves the way for broader strategies in immunoprecision medicine.
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Chatterjee N, Walker GC. Mechanisms of DNA damage, repair, and mutagenesis. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2017; 58:235-263. [PMID: 28485537 PMCID: PMC5474181 DOI: 10.1002/em.22087] [Citation(s) in RCA: 1185] [Impact Index Per Article: 148.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 03/16/2017] [Indexed: 05/08/2023]
Abstract
Living organisms are continuously exposed to a myriad of DNA damaging agents that can impact health and modulate disease-states. However, robust DNA repair and damage-bypass mechanisms faithfully protect the DNA by either removing or tolerating the damage to ensure an overall survival. Deviations in this fine-tuning are known to destabilize cellular metabolic homeostasis, as exemplified in diverse cancers where disruption or deregulation of DNA repair pathways results in genome instability. Because routinely used biological, physical and chemical agents impact human health, testing their genotoxicity and regulating their use have become important. In this introductory review, we will delineate mechanisms of DNA damage and the counteracting repair/tolerance pathways to provide insights into the molecular basis of genotoxicity in cells that lays the foundation for subsequent articles in this issue. Environ. Mol. Mutagen. 58:235-263, 2017. © 2017 Wiley Periodicals, Inc.
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Mutation tendency of mutator Plasmodium berghei with proofreading-deficient DNA polymerase δ. Sci Rep 2016; 6:36971. [PMID: 27845384 PMCID: PMC5109483 DOI: 10.1038/srep36971] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Accepted: 10/21/2016] [Indexed: 12/05/2022] Open
Abstract
In this study, we investigated the mutation tendency of a mutator rodent malaria parasite, Plasmodium berghei, with proofreading-deficient DNA polymerase δ. Wild-type and mutator parasites were maintained in mice for over 24 weeks, and the genome-wide accumulated mutations were determined by high-throughput sequencing. The mutator P. berghei had a significant preference for C/G to A/T substitutions; thus, its genome had a trend towards a higher AT content. The mutation rate was influenced by the sequence context, and mutations were markedly elevated at TCT. Some genes mutated repeatedly in replicate passage lines. In particular, knockout mutations of the AP2-G gene were frequent, which conferred strong growth advantages on parasites during the blood stage but at the cost of losing the ability to form gametocytes. This is the first report to demonstrate a biased mutation tendency in malaria parasites, and its results help to promote our basic understanding of Plasmodium genetics.
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Smith MT, Guyton KZ, Gibbons CF, Fritz JM, Portier CJ, Rusyn I, DeMarini DM, Caldwell JC, Kavlock RJ, Lambert PF, Hecht SS, Bucher JR, Stewart BW, Baan RA, Cogliano VJ, Straif K. Key Characteristics of Carcinogens as a Basis for Organizing Data on Mechanisms of Carcinogenesis. ENVIRONMENTAL HEALTH PERSPECTIVES 2016; 124:713-21. [PMID: 26600562 PMCID: PMC4892922 DOI: 10.1289/ehp.1509912] [Citation(s) in RCA: 427] [Impact Index Per Article: 47.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 11/13/2015] [Indexed: 05/10/2023]
Abstract
BACKGROUND A recent review by the International Agency for Research on Cancer (IARC) updated the assessments of the > 100 agents classified as Group 1, carcinogenic to humans (IARC Monographs Volume 100, parts A-F). This exercise was complicated by the absence of a broadly accepted, systematic method for evaluating mechanistic data to support conclusions regarding human hazard from exposure to carcinogens. OBJECTIVES AND METHODS IARC therefore convened two workshops in which an international Working Group of experts identified 10 key characteristics, one or more of which are commonly exhibited by established human carcinogens. DISCUSSION These characteristics provide the basis for an objective approach to identifying and organizing results from pertinent mechanistic studies. The 10 characteristics are the abilities of an agent to 1) act as an electrophile either directly or after metabolic activation; 2) be genotoxic; 3) alter DNA repair or cause genomic instability; 4) induce epigenetic alterations; 5) induce oxidative stress; 6) induce chronic inflammation; 7) be immunosuppressive; 8) modulate receptor-mediated effects; 9) cause immortalization; and 10) alter cell proliferation, cell death, or nutrient supply. CONCLUSION We describe the use of the 10 key characteristics to conduct a systematic literature search focused on relevant end points and construct a graphical representation of the identified mechanistic information. Next, we use benzene and polychlorinated biphenyls as examples to illustrate how this approach may work in practice. The approach described is similar in many respects to those currently being implemented by the U.S. EPA's Integrated Risk Information System Program and the U.S. National Toxicology Program. CITATION Smith MT, Guyton KZ, Gibbons CF, Fritz JM, Portier CJ, Rusyn I, DeMarini DM, Caldwell JC, Kavlock RJ, Lambert P, Hecht SS, Bucher JR, Stewart BW, Baan R, Cogliano VJ, Straif K. 2016. Key characteristics of carcinogens as a basis for organizing data on mechanisms of carcinogenesis. Environ Health Perspect 124:713-721; http://dx.doi.org/10.1289/ehp.1509912.
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Affiliation(s)
- Martyn T. Smith
- Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, Berkeley, California, USA
| | | | - Catherine F. Gibbons
- Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC, USA, and Research Triangle Park, North Carolina, USA
| | - Jason M. Fritz
- Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC, USA, and Research Triangle Park, North Carolina, USA
| | | | - Ivan Rusyn
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | - David M. DeMarini
- Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC, USA, and Research Triangle Park, North Carolina, USA
| | - Jane C. Caldwell
- Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC, USA, and Research Triangle Park, North Carolina, USA
| | - Robert J. Kavlock
- Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC, USA, and Research Triangle Park, North Carolina, USA
| | - Paul F. Lambert
- McArdle Laboratory for Cancer Research, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Stephen S. Hecht
- Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota, USA
| | - John R. Bucher
- National Toxicology Program, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, USA
| | - Bernard W. Stewart
- Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia
| | - Robert A. Baan
- International Agency for Research on Cancer, Lyon, France
| | - Vincent J. Cogliano
- Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC, USA, and Research Triangle Park, North Carolina, USA
| | - Kurt Straif
- International Agency for Research on Cancer, Lyon, France
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Gening LV, Lakhin AV, Makarova IV, Nenasheva VV, Andreeva LE, Tarantul VZ. Alterations in Synthesis and Repair of DNA during the Development of Loach Misgurnus fossilis. J Dev Biol 2016; 4:jdb4010006. [PMID: 29615575 PMCID: PMC5831811 DOI: 10.3390/jdb4010006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 01/18/2016] [Accepted: 01/20/2016] [Indexed: 01/01/2023] Open
Abstract
Using a modified radiolabeled primer extension method (we named this modification misGvA—“misincorporation of G versus A”) we have investigated the DNA synthesis and repair at early and late stages of development of loach Misgurnus fossilis. The misincorporation activity of DNA polymerase iota (Pol ι) in wild-type loach could not be detected by this method at any stage of loach development. In transgenic loach overexpressing human Pol ι we have shown that the bypassing of DNA synthesis arrest after incorporation of mismatched nucleotide by Pol ι (the T-stop) was not associated with this enzyme. Non-transgenic loach larvae are virtually lacking the capacity for error correction of DNA duplex containing a mismatched nucleotide. Such repair activity develops only in the adult fish. It appears that the initial stages of development are characterized by more intensive DNA synthesis, while in terminal stages the repair activities become more prominent. The misGvA approach clearly indicates substantial changes in the DNA synthesis intensity, although the role of particular replicative and repair DNA polymerases in this process requires further study.
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Affiliation(s)
- Leonid V Gening
- Institute of Molecular Genetics, Russian Academy of Sciences, 2 Kurchatov Square, 123182 Moscow, Russia.
| | - Andrei V Lakhin
- Institute of Molecular Genetics, Russian Academy of Sciences, 2 Kurchatov Square, 123182 Moscow, Russia.
| | - Irina V Makarova
- Institute of Molecular Genetics, Russian Academy of Sciences, 2 Kurchatov Square, 123182 Moscow, Russia.
| | - Valentina V Nenasheva
- Institute of Molecular Genetics, Russian Academy of Sciences, 2 Kurchatov Square, 123182 Moscow, Russia.
| | - Ludmila E Andreeva
- Institute of Molecular Genetics, Russian Academy of Sciences, 2 Kurchatov Square, 123182 Moscow, Russia.
| | - Vyacheslav Z Tarantul
- Institute of Molecular Genetics, Russian Academy of Sciences, 2 Kurchatov Square, 123182 Moscow, Russia.
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Choi JS, Dasari A, Hu P, Benkovic SJ, Berdis AJ. The use of modified and non-natural nucleotides provide unique insights into pro-mutagenic replication catalyzed by polymerase eta. Nucleic Acids Res 2015; 44:1022-35. [PMID: 26717984 PMCID: PMC4756837 DOI: 10.1093/nar/gkv1509] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 12/10/2015] [Indexed: 12/25/2022] Open
Abstract
This report evaluates the pro-mutagenic behavior of 8-oxo-guanine (8-oxo-G) by quantifying the ability of high-fidelity and specialized DNA polymerases to incorporate natural and modified nucleotides opposite this lesion. Although high-fidelity DNA polymerases such as pol δ and the bacteriophage T4 DNA polymerase replicating 8-oxo-G in an error-prone manner, they display remarkably low efficiencies for TLS compared to normal DNA synthesis. In contrast, pol η shows a combination of high efficiency and low fidelity when replicating 8-oxo-G. These combined properties are consistent with a pro-mutagenic role for pol η when replicating this DNA lesion. Studies using modified nucleotide analogs show that pol η relies heavily on hydrogen-bonding interactions during translesion DNA synthesis. However, nucleobase modifications such as alkylation to the N2 position of guanine significantly increase error-prone synthesis catalyzed by pol η when replicating 8-oxo-G. Molecular modeling studies demonstrate the existence of a hydrophobic pocket in pol η that participates in the increased utilization of certain hydrophobic nucleotides. A model is proposed for enhanced pro-mutagenic replication catalyzed by pol η that couples efficient incorporation of damaged nucleotides opposite oxidized DNA lesions created by reactive oxygen species. The biological implications of this model toward increasing mutagenic events in lung cancer are discussed.
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Affiliation(s)
- Jung-Suk Choi
- Department of Chemistry, Cleveland State University, 2351 Euclid Avenue, Cleveland, OH 44115, USA
| | - Anvesh Dasari
- Department of Chemistry, Cleveland State University, 2351 Euclid Avenue, Cleveland, OH 44115, USA
| | - Peter Hu
- Department of Chemistry, The Pennsylvania State University, 413 Wartik Building, University Park, PA 16802, USA
| | - Stephen J Benkovic
- Department of Chemistry, The Pennsylvania State University, 413 Wartik Building, University Park, PA 16802, USA
| | - Anthony J Berdis
- Department of Chemistry, Cleveland State University, 2351 Euclid Avenue, Cleveland, OH 44115, USA Center for Gene Regulation in Health and Disease, Cleveland State University, 2351 Euclid Avenue, Cleveland, OH 44115, USA Case Comprehensive Cancer Center, 10900 Euclid Avenue, Cleveland OH 44106, USA
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Lujan SA, Williams JS, Kunkel TA. Eukaryotic genome instability in light of asymmetric DNA replication. Crit Rev Biochem Mol Biol 2015; 51:43-52. [PMID: 26822554 DOI: 10.3109/10409238.2015.1117055] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The eukaryotic nuclear genome is replicated asymmetrically, with the leading strand replicated continuously and the lagging strand replicated as discontinuous Okazaki fragments that are subsequently joined. Both strands are replicated with high fidelity, but the processes used to achieve high fidelity are likely to differ. Here we review recent studies of similarities and differences in the fidelity with which the three major eukaryotic replicases, DNA polymerases α, δ, and ɛ, replicate the leading and lagging strands with high nucleotide selectivity and efficient proofreading. We then relate the asymmetric fidelity at the replication fork to the efficiency of DNA mismatch repair, ribonucleotide excision repair and topoisomerase 1 activity.
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Affiliation(s)
- Scott A Lujan
- a Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences , Research Triangle Park , NC , USA
| | - Jessica S Williams
- a Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences , Research Triangle Park , NC , USA
| | - Thomas A Kunkel
- a Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences , Research Triangle Park , NC , USA
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Richter KS, Götz M, Winter S, Jeske H. The contribution of translesion synthesis polymerases on geminiviral replication. Virology 2015; 488:137-48. [PMID: 26638018 DOI: 10.1016/j.virol.2015.10.027] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 10/26/2015] [Accepted: 10/28/2015] [Indexed: 12/25/2022]
Abstract
Geminiviruses multiply primarily in the plant phloem, but never in meristems. Their Rep protein can activate DNA synthesis in differentiated cells. However, when their single-stranded DNA is injected into the phloem by insects, no Rep is present for inducing initial complementary strand replication. Considering a contribution of translesion synthesis (TLS) polymerases in plants, four of them (Polη, Polζ, Polκ, Rev1) are highly and constitutively expressed in differentiated tissues like the phloem. Two geminiviruses (Euphorbia yellow mosaic virus, Cleome leaf crumple virus), inoculated either biolistically or by whiteflies, replicated in Arabidopsis thaliana mutant lines of these genes to the same extent as in wild type plants. Comparative deep sequencing of geminiviral DNAs, however, showed a high exchange rate (10(-4)-10(-3)) similar to the phylogenetic variation described before and a significant difference in nucleotide substation rates if Polη and Polζ were absent, with a differential response to the viral DNA components.
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Affiliation(s)
- Kathrin S Richter
- Institute of Biomaterials and Biomolecular Systems, Department of Molecular Biology and Plant Virology, University of Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany
| | - Monika Götz
- Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Messeweg 11-12, D-38104 Braunschweig, Germany
| | - Stephan Winter
- Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Messeweg 11-12, D-38104 Braunschweig, Germany
| | - Holger Jeske
- Institute of Biomaterials and Biomolecular Systems, Department of Molecular Biology and Plant Virology, University of Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany.
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Donigan KA, Cerritelli SM, McDonald JP, Vaisman A, Crouch RJ, Woodgate R. Unlocking the steric gate of DNA polymerase η leads to increased genomic instability in Saccharomyces cerevisiae. DNA Repair (Amst) 2015; 35:1-12. [PMID: 26340535 PMCID: PMC4651834 DOI: 10.1016/j.dnarep.2015.07.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Revised: 07/18/2015] [Accepted: 07/21/2015] [Indexed: 11/26/2022]
Abstract
DNA polymerase η (pol η) is best characterized for its ability to perform accurate and efficient translesion DNA synthesis (TLS) through cyclobutane pyrimidine dimers (CPDs). To ensure accurate bypass the polymerase is not only required to select the correct base, but also discriminate between NTPs and dNTPs. Most DNA polymerases have a conserved "steric gate" residue which functions to prevent incorporation of NMPs during DNA synthesis. Here, we demonstrate that the Phe35 residue of Saccharomyces cerevisiae pol η functions as a steric gate to limit the use of ribonucleotides during polymerization both in vitro and in vivo. Unlike the related pol ι enzyme, wild-type pol η does not readily incorporate NMPs in vitro. In contrast, a pol η F35A mutant incorporates NMPs on both damaged and undamaged DNA in vitro with a high degree of base selectivity. An S.cerevisiae strain expressing pol η F35A (rad30-F35A) that is also deficient for nucleotide excision repair (rad1Δ) and the TLS polymerase, pol ζ (rev3Δ), is extremely sensitive to UV-light. The sensitivity is due, in part, to RNase H2 activity, as an isogenic rnh201Δ strain is roughly 50-fold more UV-resistant than its RNH201(+) counterpart. Interestingly the rad1Δ rev3Δ rad30-F35A rnh201Δ strain exhibits a significant increase in the extent of spontaneous mutagenesis with a spectrum dominated by 1bp deletions at runs of template Ts. We hypothesize that the increased mutagenesis is due to rA incorporation at these sites and that the short poly rA tract is subsequently repaired in an error-prone manner by a novel repair pathway that is specifically targeted to polyribonucleotide tracks. These data indicate that under certain conditions, pol η can compete with the cell's replicases and gain access to undamaged genomic DNA. Such observations are consistent with a role for pol η in replicating common fragile sites (CFS) in human cells.
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Affiliation(s)
- Katherine A Donigan
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, USA
| | - Susana M Cerritelli
- Program in Genomics of Differentiation, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - John P McDonald
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, USA
| | - Alexandra Vaisman
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, USA
| | - Robert J Crouch
- Program in Genomics of Differentiation, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Roger Woodgate
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, USA.
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Disruption of Transcriptional Coactivator Sub1 Leads to Genome-Wide Re-distribution of Clustered Mutations Induced by APOBEC in Active Yeast Genes. PLoS Genet 2015; 11:e1005217. [PMID: 25941824 PMCID: PMC4420506 DOI: 10.1371/journal.pgen.1005217] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 04/13/2015] [Indexed: 12/21/2022] Open
Abstract
Mutations in genomes of species are frequently distributed non-randomly, resulting in mutation clusters, including recently discovered kataegis in tumors. DNA editing deaminases play the prominent role in the etiology of these mutations. To gain insight into the enigmatic mechanisms of localized hypermutagenesis that lead to cluster formation, we analyzed the mutational single nucleotide variations (SNV) data obtained by whole-genome sequencing of drug-resistant mutants induced in yeast diploids by AID/APOBEC deaminase and base analog 6-HAP. Deaminase from sea lamprey, PmCDA1, induced robust clusters, while 6-HAP induced a few weak ones. We found that PmCDA1, AID, and APOBEC1 deaminases preferentially mutate the beginning of the actively transcribed genes. Inactivation of transcription initiation factor Sub1 strongly reduced deaminase-induced can1 mutation frequency, but, surprisingly, did not decrease the total SNV load in genomes. However, the SNVs in the genomes of the sub1 clones were re-distributed, and the effect of mutation clustering in the regions of transcription initiation was even more pronounced. At the same time, the mutation density in the protein-coding regions was reduced, resulting in the decrease of phenotypically detected mutants. We propose that the induction of clustered mutations by deaminases involves: a) the exposure of ssDNA strands during transcription and loss of protection of ssDNA due to the depletion of ssDNA-binding proteins, such as Sub1, and b) attainment of conditions favorable for APOBEC action in subpopulation of cells, leading to enzymatic deamination within the currently expressed genes. This model is applicable to both the initial and the later stages of oncogenic transformation and explains variations in the distribution of mutations and kataegis events in different tumor cells. Genomes of tumors are heavily enriched with mutations. Some of these mutations are distributed non-randomly, forming mutational clusters. Editing cytosine deaminases from APOBEC superfamily are responsible for the formation of many of these clusters. We have expressed APOBEC enzyme in diploid yeast cells and found that most of the mutations occur in the beginning of the active genes, where transcription starts. Clusters of mutations overlapped with promoters/transcription start sites. This is likely due to the weaker protection of ssDNA, an ultimate APOBEC deaminase enzyme target, in the beginning of the genes. This hypothesis was reinforced by the finding that inactivation of Sub1 transcription initiation factor, which is found predominantly in the regions of transcription initiation, leads to further increase in mutagenesis in the beginning of the genes. Interestingly, the total number of mutations in the genomes of Sub1-deficient clones did not change, despite the 100-fold decrease in frequency of mutants in a reporter gene. Thus, the drastic change in genome-wide distribution of mutations can be caused by inactivation of a single gene. We propose that the loss of ssDNA protection factors causes formation of mutation clusters in human cancer.
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Guarné A, Charbonnier JB. Insights from a decade of biophysical studies on MutL: Roles in strand discrimination and mismatch removal. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2015; 117:149-156. [PMID: 25701376 DOI: 10.1016/j.pbiomolbio.2015.02.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Revised: 01/31/2015] [Accepted: 02/09/2015] [Indexed: 11/18/2022]
Abstract
DNA mismatch repair (MMR) is a conserved pathway that safeguards genome integrity by correcting replication errors. The coordinated actions of two proteins (MutS and MutL) initiate the mismatch repair response and defects in the genes encoding for these proteins have been linked to sporadic and hereditary cancers. The basic steps to repair a mismatch include recognizing the mismatch, discriminating the newly synthesized from the parental strand, removing and re-synthesizing the erroneous strand. Although the DNA mismatch repair pathway has been extensively studied over the last four decades, the strand discrimination mechanism has remained elusive in most organisms. Work over the last decade has brought significant progress onto this step of the pathway, in turn ascribing new and critical roles to the MutL protein. In this review, we describe biochemical, biophysical and structural analyses that have clarified how MutL aids at discriminating the newly synthesized strand from its template and marking it for removal.
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Affiliation(s)
- Alba Guarné
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
| | - Jean-Baptiste Charbonnier
- CEA, IBITECS, Laboratoire de Biologie Structurale et Radiobiologie, CE-Saclay, F-91191 Gif sur Yvette, France; CNRS, URA 2096, F-91191 Gif sur Yvette, France.
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mTOR Signaling in Endometrial Cancer: From a Molecular and Therapeutic Point of View. CURRENT OBSTETRICS AND GYNECOLOGY REPORTS 2015. [DOI: 10.1007/s13669-014-0103-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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