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Wang X, Zhao X, Yu Z, Fan T, Guo Y, Liang J, Wang Y, Zhan J, Chen G, Zhou C, Zhang X, Li X, Chen X. Rtt105 stimulates Rad51-ssDNA assembly and orchestrates Rad51 and RPA actions to promote homologous recombination repair. Proc Natl Acad Sci U S A 2024; 121:e2402262121. [PMID: 39145931 PMCID: PMC11348298 DOI: 10.1073/pnas.2402262121] [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: 02/02/2024] [Accepted: 07/09/2024] [Indexed: 08/16/2024] Open
Abstract
Homologous recombination (HR) is essential for the maintenance of genome stability. During HR, Replication Protein A (RPA) rapidly coats the 3'-tailed single-strand DNA (ssDNA) generated by end resection. Then, the ssDNA-bound RPA must be timely replaced by Rad51 recombinase to form Rad51 nucleoprotein filaments that drive homology search and HR repair. How cells regulate Rad51 assembly dynamics and coordinate RPA and Rad51 actions to ensure proper HR remains poorly understood. Here, we identified that Rtt105, a Ty1 transposon regulator, acts to stimulate Rad51 assembly and orchestrate RPA and Rad51 actions during HR. We found that Rtt105 interacts with Rad51 in vitro and in vivo and restrains the adenosine 5' triphosphate (ATP) hydrolysis activity of Rad51. We showed that Rtt105 directly stimulates dynamic Rad51-ssDNA assembly, strand exchange, and D-loop formation in vitro. Notably, we found that Rtt105 physically regulates the binding of Rad51 and RPA to ssDNA via different motifs and that both regulations are necessary and epistatic in promoting Rad51 nucleation, strand exchange, and HR repair. Consequently, disrupting either of the interactions impaired HR and conferred DNA damage sensitivity, underscoring the importance of Rtt105 in orchestrating the actions of Rad51 and RPA. Our work reveals additional layers of mechanisms regulating Rad51 filament dynamics and the coordination of HR.
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Affiliation(s)
- Xuejie Wang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Department of Radiation Oncology, Renmin Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan430072, China
| | - Xiaocong Zhao
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Department of Radiation Oncology, Renmin Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan430072, China
| | - Zhengshi Yu
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Department of Radiation Oncology, Renmin Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan430072, China
| | - Tianai Fan
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Department of Radiation Oncology, Renmin Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan430072, China
| | - Yunjing Guo
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Department of Radiation Oncology, Renmin Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan430072, China
| | - Jianqiang Liang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Department of Radiation Oncology, Renmin Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan430072, China
| | - Yanyan Wang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Department of Radiation Oncology, Renmin Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan430072, China
| | - Jingfei Zhan
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Department of Radiation Oncology, Renmin Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan430072, China
| | - Guifang Chen
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Department of Radiation Oncology, Renmin Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan430072, China
| | - Chun Zhou
- School of Public Health, Zhejiang University School of Medicine, Hangzhou310058, China
| | - Xinghua Zhang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Department of Radiation Oncology, Renmin Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan430072, China
| | - Xiangpan Li
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Department of Radiation Oncology, Renmin Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan430072, China
| | - Xuefeng Chen
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Department of Radiation Oncology, Renmin Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan430072, China
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2
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Wysong BC, Schuck PL, Sridharan M, Carrison S, Murakami Y, Balakrishnan L, Stewart JA. Human CST Stimulates Base Excision Repair to Prevent the Accumulation of Oxidative DNA Damage. J Mol Biol 2024; 436:168672. [PMID: 38908783 DOI: 10.1016/j.jmb.2024.168672] [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: 02/14/2024] [Revised: 06/14/2024] [Accepted: 06/17/2024] [Indexed: 06/24/2024]
Abstract
CTC1-STN1-TEN1 (CST) is a single-stranded DNA binding protein vital for telomere length maintenance with additional genome-wide roles in DNA replication and repair. While CST was previously shown to function in double-strand break repair and promote replication restart, it is currently unclear whether it has specialized roles in other DNA repair pathways. Proper and efficient repair of DNA is critical to protecting genome integrity. Telomeres and other G-rich regions are strongly predisposed to oxidative DNA damage in the form of 8-oxoguanines, which are typically repaired by the base-excision repair (BER) pathway. Moreover, recent studies suggest that CST functions in the repair of oxidative DNA lesions. Therefore, we tested whether CST interacts with and regulates BER protein activity. Here, we show that CST robustly stimulates proteins involved in BER, including OGG1, Pol β, APE1, and LIGI, on both telomeric and non-telomeric DNA substrates. Biochemical reconstitution of the pathway indicates that CST stimulates BER. Finally, knockout of STN1 or CTC1 leads to increased levels of 8-oxoguanine, suggesting defective BER in the absence of CST. Combined, our results define an undiscovered function of CST in BER, where it acts as a stimulatory factor to promote efficient genome-wide oxidative repair.
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Affiliation(s)
- Brandon C Wysong
- Department of Biology, School of Science, Indiana University, Indianapolis, IN, USA
| | - P Logan Schuck
- Department of Biological Sciences, University of South Carolina, Columbia, USA
| | - Madhumita Sridharan
- Department of Biology, School of Science, Indiana University, Indianapolis, IN, USA
| | - Sophie Carrison
- Department of Biology, School of Science, Indiana University, Indianapolis, IN, USA
| | - Yuichihiro Murakami
- Department of Biology, School of Science, Indiana University, Indianapolis, IN, USA
| | - Lata Balakrishnan
- Department of Biology, School of Science, Indiana University, Indianapolis, IN, USA.
| | - Jason A Stewart
- Department of Biological Sciences, University of South Carolina, Columbia, USA; Department of Biology, Western Kentucky University, Bowling Green, KY, USA.
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3
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Sang PB, Jaiswal RK, Lyu X, Chai W. Human CST complex restricts excessive PrimPol repriming upon UV induced replication stress by suppressing p21. Nucleic Acids Res 2024; 52:3778-3793. [PMID: 38348929 DOI: 10.1093/nar/gkae078] [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: 09/05/2023] [Revised: 01/18/2024] [Accepted: 01/26/2024] [Indexed: 04/25/2024] Open
Abstract
DNA replication stress, caused by various endogenous and exogenous agents, halt or stall DNA replication progression. Cells have developed diverse mechanisms to tolerate and overcome replication stress, enabling them to continue replication. One effective strategy to overcome stalled replication involves skipping the DNA lesion using a specialized polymerase known as PrimPol, which reinitiates DNA synthesis downstream of the damage. However, the mechanism regulating PrimPol repriming is largely unclear. In this study, we observe that knockdown of STN1 or CTC1, components of the CTC1/STN1/TEN1 complex, leads to enhanced replication progression following UV exposure. We find that such increased replication is dependent on PrimPol, and PrimPol recruitment to stalled forks increases upon CST depletion. Moreover, we find that p21 is upregulated in STN1-depleted cells in a p53-independent manner, and p21 depletion restores normal replication rates caused by STN1 deficiency. We identify that p21 interacts with PrimPol, and STN1 depletion stimulates p21-PrimPol interaction and facilitates PrimPol recruitment to stalled forks. Our findings reveal a previously undescribed interplay between CST, PrimPol and p21 in promoting repriming in response to stalled replication, and shed light on the regulation of PrimPol repriming at stalled forks.
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Affiliation(s)
- Pau Biak Sang
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
- Department of Microbiology, University of Delhi South Campus, New Delhi, India
| | - Rishi K Jaiswal
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA
| | - Xinxing Lyu
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Weihang Chai
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA
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4
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Knowles S, Chai W. Conditional Depletion of STN1 in Mouse Embryonic Fibroblasts. Bio Protoc 2024; 14:e4977. [PMID: 38686350 PMCID: PMC11056013 DOI: 10.21769/bioprotoc.4977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 03/20/2024] [Accepted: 03/21/2024] [Indexed: 05/02/2024] Open
Abstract
The CTC1-STN1-TEN1 (CST) complex is a single-strand DNA-binding protein complex that plays an important role in genome maintenance in various model eukaryotes. Dysfunction of CST is the underlying cause of the rare genetic disorder known as Coats plus disease. In addition, down regulation of STN1 promotes colorectal cancer development in mice. While prior studies have utilized RNAi to knock down CST components in mammalian cells, this approach is associated with off-target effects. Attempts to employ CRISPR/Cas9-based knockout of CST components in somatic cell lines have been unsuccessful due to CST's indispensable role in DNA replication and cell proliferation. To address these challenges, we outline a novel approach utilizing a Cre-loxP-based conditional knockout in mouse embryonic fibroblasts (MEFs). This method offers an alternative means to investigate the function and characteristics of the CST complex in mammalian systems, potentially shedding new light on its roles in genome maintenance. Key features • Conditional depletion of mammalian STN1 using mouse embryonic fibroblast (MEFs). • Analysis of oxidative damage sensitivity using STN1-depleted MEFs. • This protocol requires Stn1flox/flox mice.
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Affiliation(s)
- Sara Knowles
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA
| | - Weihang Chai
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA
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5
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Olson CL, Wuttke DS. Guardians of the Genome: How the Single-Stranded DNA-Binding Proteins RPA and CST Facilitate Telomere Replication. Biomolecules 2024; 14:263. [PMID: 38540683 PMCID: PMC10968030 DOI: 10.3390/biom14030263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 02/02/2024] [Accepted: 02/20/2024] [Indexed: 04/26/2024] Open
Abstract
Telomeres act as the protective caps of eukaryotic linear chromosomes; thus, proper telomere maintenance is crucial for genome stability. Successful telomere replication is a cornerstone of telomere length regulation, but this process can be fraught due to the many intrinsic challenges telomeres pose to the replication machinery. In addition to the famous "end replication" problem due to the discontinuous nature of lagging strand synthesis, telomeres require various telomere-specific steps for maintaining the proper 3' overhang length. Bulk telomere replication also encounters its own difficulties as telomeres are prone to various forms of replication roadblocks. These roadblocks can result in an increase in replication stress that can cause replication forks to slow, stall, or become reversed. Ultimately, this leads to excess single-stranded DNA (ssDNA) that needs to be managed and protected for replication to continue and to prevent DNA damage and genome instability. RPA and CST are single-stranded DNA-binding protein complexes that play key roles in performing this task and help stabilize stalled forks for continued replication. The interplay between RPA and CST, their functions at telomeres during replication, and their specialized features for helping overcome replication stress at telomeres are the focus of this review.
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Affiliation(s)
- Conner L. Olson
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Deborah S. Wuttke
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO 80309, USA
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6
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Liu MY, Lin KR, Chien YL, Yang BZ, Tsui LY, Chu HP, Wu CSP. ATR phosphorylates DHX9 at serine 321 to suppress R-loop accumulation upon genotoxic stress. Nucleic Acids Res 2024; 52:204-222. [PMID: 37930853 PMCID: PMC10783509 DOI: 10.1093/nar/gkad973] [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: 07/13/2023] [Revised: 09/19/2023] [Accepted: 10/16/2023] [Indexed: 11/08/2023] Open
Abstract
Aberrant DNA/RNA hybrids (R-loops) formed during transcription and replication disturbances pose threats to genome stability. DHX9 is an RNA helicase involved in R-loop resolution, but how DHX9 is regulated in response to genotoxic stress remains unclear. Here we report that DHX9 is phosphorylated at S321 and S688, with S321 phosphorylation primarily induced by ATR after DNA damage. Phosphorylation of DHX9 at S321 promotes its interaction with γH2AX, BRCA1 and RPA, and is required for its association with R-loops under genotoxic stress. Inhibition of ATR or expression of the non-phosphorylatable DHX9S321A prevents DHX9 from interacting with RPA and R-loops, leading to the accumulation of stress-induced R-loops. Furthermore, depletion of RPA reduces the association between DHX9 and γH2AX, and in vitro binding analysis confirms a direct interaction between DHX9 and RPA. Notably, cells with the non-phosphorylatable DHX9S321A variant exhibit hypersensitivity to genotoxic stress, while those expressing the phosphomimetic DHX9S321D variant prevent R-loop accumulation and display resistance to DNA damage agents. In summary, we uncover a new mechanism by which ATR directly regulates DHX9 through phosphorylation to eliminate stress-induced R-loops.
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Affiliation(s)
- Mei-Yin Liu
- Department and Graduate Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei 100233, Taiwan
| | - Keng-Ru Lin
- Department and Graduate Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei 100233, Taiwan
| | - Yuh-Ling Chien
- Department and Graduate Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei 100233, Taiwan
| | - Bing-Ze Yang
- Department and Graduate Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei 100233, Taiwan
| | - Li-Yu Tsui
- Department and Graduate Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei 100233, Taiwan
| | | | - Ching-Shyi Peter Wu
- Department and Graduate Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei 100233, Taiwan
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7
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Amritha PP, Shah JM. Essential role of the BRCA2B gene in somatic homologous recombination in Arabidopsis thaliana. BIOTECHNOLOGIA 2023; 104:371-380. [PMID: 38213474 PMCID: PMC10777725 DOI: 10.5114/bta.2023.132773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 06/15/2023] [Accepted: 08/29/2023] [Indexed: 01/13/2024] Open
Abstract
Constant exposure to various environmental and endogenous stresses can cause structural DNA damage, resulting in genome instability. Higher eukaryotic cells deploy conserved DNA repair systems, which include various DNA repair pathways, to maintain genome stability. Homologous recombination (HR), one of these repair pathways, involves multiple proteins. BRCA2, one of the proteins in the HR pathway, is of substantial research interest in humans because it is an oncogene. However, the study of this gene is limited due to the lack of availability of homozygous BRCA2-knockout mutants in mammals, which results in embryonic lethality. Arabidopsis thaliana has two copies of the BRCA2 homologs: BRCA2A and BRCA2B . Therefore, the single mutants remain nonlethal and fertile in Arabidopsis. The BRCA2A homolog, which plays a significant role in the HR pathway of germline cells and during the defense response, is well-studied in Arabidopsis. Our study focuses on the functional characterization of the BRCA2B homolog in the somatic cells of Arabidopsis, using the homozygous ΔBRCA2B mutant line. The phenotypic differences of ΔBRCA2B mutants were characterized and compared with wild Arabidopsis plants. The role of BRCA2B in spontaneous somatic HR (SHR) was studied using the ΔBRCA2B-gus detector line. ΔBRCA2B plants have a 6.3-fold lower SHR frequency than the control detector plants. Expression of four other HR pathway genes, including BRE, BRCC36A, RAD50, and RAD54, was significantly reduced in ΔBRCA2B mutants. Thus, our findings convey that the BRCA2B homolog plays an important role in maintaining spontaneous SHR rates and has a direct or indirect regulatory effect on the expression of other HR-related genes.
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Affiliation(s)
| | - Jasmine M. Shah
- Department of Plant Science, Central University of Kerala, Kasaragod, Kerala, India
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8
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Jaiswal RK, Lei KH, Chastain M, Wang Y, Shiva O, Li S, You Z, Chi P, Chai W. CaMKK2 and CHK1 phosphorylate human STN1 in response to replication stress to protect stalled forks from aberrant resection. Nat Commun 2023; 14:7882. [PMID: 38036565 PMCID: PMC10689503 DOI: 10.1038/s41467-023-43685-2] [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: 04/19/2023] [Accepted: 11/16/2023] [Indexed: 12/02/2023] Open
Abstract
Keeping replication fork stable is essential for safeguarding genome integrity; hence, its protection is highly regulated. The CTC1-STN1-TEN1 (CST) complex protects stalled forks from aberrant MRE11-mediated nascent strand DNA degradation (NSD). However, the activation mechanism for CST at forks is unknown. Here, we report that STN1 is phosphorylated in its intrinsic disordered region. Loss of STN1 phosphorylation reduces the replication stress-induced STN1 localization to stalled forks, elevates NSD, increases MRE11 access to stalled forks, and decreases RAD51 localization at forks, leading to increased genome instability under perturbed DNA replication condition. STN1 is phosphorylated by both the ATR-CHK1 and the calcium-sensing kinase CaMKK2 in response to hydroxyurea/aphidicolin treatment or elevated cytosolic calcium concentration. Cancer-associated STN1 variants impair STN1 phosphorylation, conferring inability of fork protection. Collectively, our study uncovers that CaMKK2 and ATR-CHK1 target STN1 to enable its fork protective function, and suggests an important role of STN1 phosphorylation in cancer development.
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Affiliation(s)
- Rishi Kumar Jaiswal
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Kai-Hang Lei
- Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
| | - Megan Chastain
- Office of Research, Washington State University, Spokane, WA, USA
| | - Yuan Wang
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, USA
| | - Olga Shiva
- Office of Research, Washington State University, Spokane, WA, USA
| | - Shan Li
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Zhongsheng You
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Peter Chi
- Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Weihang Chai
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA.
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Hara T, Nakaoka H, Miyoshi T, Ishikawa F. The CST complex facilitates cell survival under oxidative genotoxic stress. PLoS One 2023; 18:e0289304. [PMID: 37590191 PMCID: PMC10434909 DOI: 10.1371/journal.pone.0289304] [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: 03/22/2023] [Accepted: 07/15/2023] [Indexed: 08/19/2023] Open
Abstract
Genomic DNA is constantly exposed to a variety of genotoxic stresses, and it is crucial for organisms to be equipped with mechanisms for repairing the damaged genome. Previously, it was demonstrated that the mammalian CST (CTC1-STN1-TEN1) complex, which was originally identified as a single-stranded DNA-binding trimeric protein complex essential for telomere maintenance, is required for survival in response to hydroxyurea (HU), which induces DNA replication fork stalling. It is still unclear, however, how the CST complex is involved in the repair of diverse types of DNA damage induced by oxidizing agents such as H2O2. STN1 knockdown (KD) sensitized HeLa cells to high doses of H2O2. While H2O2 induced DNA strand breaks throughout the cell cycle, STN1 KD cells were as resistant as control cells to H2O2 treatment when challenged in the G1 phase of the cell cycle, but they were sensitive when exposed to H2O2 in S/G2/M phase. STN1 KD cells showed a failure of DNA synthesis and RAD51 foci formation upon H2O2 treatment. Chemical inhibition of RAD51 in shSTN1 cells did not exacerbate the sensitivity to H2O2, implying that the CST complex and RAD51 act in the same pathway. Collectively, our results suggest that the CST complex is required for maintaining genomic stability in response to oxidative DNA damage, possibly through RAD51-dependent DNA repair/protection mechanisms.
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Affiliation(s)
- Tomohiko Hara
- Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
- Radiation Biology Center, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Hidenori Nakaoka
- Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
- Radiation Biology Center, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Tomoicihiro Miyoshi
- Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
- Radiation Biology Center, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
- Laboratory for Retrotransposon Dynamics, RIKEN Center for Integrative Medical Sciences, Yokohama, Japan
| | - Fuyuki Ishikawa
- Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
- Radiation Biology Center, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
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10
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Olson CL, Barbour AT, Wieser TA, Wuttke DS. RPA engages telomeric G-quadruplexes more effectively than CST. Nucleic Acids Res 2023; 51:5073-5086. [PMID: 37140062 PMCID: PMC10250233 DOI: 10.1093/nar/gkad315] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Revised: 04/11/2023] [Accepted: 04/21/2023] [Indexed: 05/05/2023] Open
Abstract
G-quadruplexes (G4s) are a set of stable secondary structures that form within guanine-rich regions of single-stranded nucleic acids that pose challenges for DNA maintenance. The G-rich DNA sequence at telomeres has a propensity to form G4s of various topologies. The human protein complexes Replication Protein A (RPA) and CTC1-STN1-TEN1 (CST) are implicated in managing G4s at telomeres, leading to DNA unfolding and allowing telomere replication to proceed. Here, we use fluorescence anisotropy equilibrium binding measurements to determine the ability of these proteins to bind various telomeric G4s. We find that the ability of CST to specifically bind G-rich ssDNA is substantially inhibited by the presence of G4s. In contrast, RPA tightly binds telomeric G4s, showing negligible changes in affinity for G4 structure compared to linear ssDNAs. Using a mutagenesis strategy, we found that RPA DNA-binding domains work together for G4 binding, and simultaneous disruption of these domains reduces the affinity of RPA for G4 ssDNA. The relative inability of CST to disrupt G4s, combined with the greater cellular abundance of RPA, suggests that RPA could act as a primary protein complex responsible for resolving G4s at telomeres.
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Affiliation(s)
- Conner L Olson
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO80309, USA
| | - Alexandra T Barbour
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO80309, USA
| | - Thomas A Wieser
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO80309, USA
| | - Deborah S Wuttke
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO80309, USA
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11
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Liu G, Li J, He B, Yan J, Zhao J, Wang X, Zhao X, Xu J, Wu Y, Zhang S, Gan X, Zhou C, Li X, Zhang X, Chen X. Bre1/RNF20 promotes Rad51-mediated strand exchange and antagonizes the Srs2/FBH1 helicases. Nat Commun 2023; 14:3024. [PMID: 37230987 DOI: 10.1038/s41467-023-38617-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 05/10/2023] [Indexed: 05/27/2023] Open
Abstract
Central to homologous recombination (HR) is the assembly of Rad51 recombinase on single-strand DNA (ssDNA), forming the Rad51-ssDNA filament. How the Rad51 filament is efficiently established and sustained remains partially understood. Here, we find that the yeast ubiquitin ligase Bre1 and its human homolog RNF20, a tumor suppressor, function as recombination mediators, promoting Rad51 filament formation and subsequent reactions via multiple mechanisms independent of their ligase activities. We show that Bre1/RNF20 interacts with Rad51, directs Rad51 to ssDNA, and facilitates Rad51-ssDNA filament assembly and strand exchange in vitro. In parallel, Bre1/RNF20 interacts with the Srs2 or FBH1 helicase to counteract their disrupting effect on the Rad51 filament. We demonstrate that the above functions of Bre1/RNF20 contribute to HR repair in cells in a manner additive to the mediator protein Rad52 in yeast or BRCA2 in human. Thus, Bre1/RNF20 provides an additional layer of mechanism to directly control Rad51 filament dynamics.
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Affiliation(s)
- Guangxue Liu
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Department of Oncology, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
| | - Jimin Li
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Department of Oncology, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
| | - Boxue He
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Jiaqi Yan
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Department of Oncology, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
| | - Jingyu Zhao
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Department of Oncology, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
| | - Xuejie Wang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Department of Oncology, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
| | - Xiaocong Zhao
- The Institute for Advanced Studies, Wuhan University, Wuhan, China
| | - Jingyan Xu
- Department of Hematology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, China
| | - Yeyao Wu
- School of Public Health, Zhejiang University School of Medicine, Hangzhou, China
| | - Simin Zhang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Department of Oncology, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
| | - Xiaoli Gan
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Department of Oncology, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
| | - Chun Zhou
- School of Public Health, Zhejiang University School of Medicine, Hangzhou, China
| | - Xiangpan Li
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Department of Oncology, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
| | - Xinghua Zhang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Department of Oncology, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China
- The Institute for Advanced Studies, Wuhan University, Wuhan, China
| | - Xuefeng Chen
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Department of Oncology, Renmin Hospital of Wuhan University, Wuhan University, Wuhan, China.
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12
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Nguyen DD, Kim E, Le NT, Ding X, Jaiswal RK, Kostlan RJ, Nguyen TNT, Shiva O, Le MT, Chai W. Deficiency in mammalian STN1 promotes colon cancer development via inhibiting DNA repair. SCIENCE ADVANCES 2023; 9:eadd8023. [PMID: 37163605 PMCID: PMC10171824 DOI: 10.1126/sciadv.add8023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 04/05/2023] [Indexed: 05/12/2023]
Abstract
Despite the high lethality of colorectal cancers (CRCs), only a limited number of genetic risk factors are identified. The mammalian ssDNA-binding protein complex CTC1-STN1-TEN1 protects genome stability, yet its role in tumorigenesis is unknown. Here, we show that attenuated CTC1/STN1 expression is common in CRCs. We generated an inducible STN1 knockout mouse model and found that STN1 deficiency in young adult mice increased CRC incidence, tumor size, and tumor load. CRC tumors exhibited enhanced proliferation, reduced apoptosis, and elevated DNA damage and replication stress. We found that STN1 deficiency down-regulated multiple DNA glycosylases, resulting in defective base excision repair (BER) and accumulation of oxidative damage. Collectively, this study identifies STN1 deficiency as a risk factor for CRC and implicates the previously unknown STN1-BER axis in protecting colon tissues from oxidative damage, therefore providing insights into the CRC tumor-suppressing mechanism.
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Affiliation(s)
- Dinh Duc Nguyen
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Eugene Kim
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Nhat Thong Le
- School of Biotechnology, International University, Ho Chi Minh City, Vietnam
| | - Xianzhong Ding
- Department of Pathology, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Rishi Kumar Jaiswal
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Raymond Joseph Kostlan
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Thi Ngoc Thanh Nguyen
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Olga Shiva
- Office of Research, Washington State University-Spokane, Spokane, WA, USA
| | - Minh Thong Le
- School of Biotechnology, International University, Ho Chi Minh City, Vietnam
| | - Weihang Chai
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
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