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Zhang X, Xu J, Hu J, Zhang S, Hao Y, Zhang D, Qian H, Wang D, Fu XD. Cockayne Syndrome Linked to Elevated R-Loops Induced by Stalled RNA Polymerase II during Transcription Elongation. Nat Commun 2024; 15:6031. [PMID: 39019869 PMCID: PMC11255242 DOI: 10.1038/s41467-024-50298-w] [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: 04/07/2023] [Accepted: 07/04/2024] [Indexed: 07/19/2024] Open
Abstract
Mutations in the Cockayne Syndrome group B (CSB) gene cause cancer in mice, but premature aging and severe neurodevelopmental defects in humans. CSB, a member of the SWI/SNF family of chromatin remodelers, plays diverse roles in regulating gene expression and transcription-coupled nucleotide excision repair (TC-NER); however, these functions do not explain the distinct phenotypic differences observed between CSB-deficient mice and humans. During investigating Cockayne Syndrome-associated genome instability, we uncover an intrinsic mechanism that involves elongating RNA polymerase II (RNAPII) undergoing transient pauses at internal T-runs where CSB is required to propel RNAPII forward. Consequently, CSB deficiency retards RNAPII elongation in these regions, and when coupled with G-rich sequences upstream, exacerbates genome instability by promoting R-loop formation. These R-loop prone motifs are notably abundant in relatively long genes related to neuronal functions in the human genome, but less prevalent in the mouse genome. These findings provide mechanistic insights into differential impacts of CSB deficiency on mice versus humans and suggest that the manifestation of the Cockayne Syndrome phenotype in humans results from the progressive evolution of mammalian genomes.
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Affiliation(s)
- Xuan Zhang
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA, USA
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, USA
| | - Jun Xu
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA
- Genetics and Metabolism Department, The Children's Hospital, School of Medicine, Zhejiang University, National Clinical Research Center for Child Health, Hangzhou, China
- The Institute of Translational Medicine, School of Medicine, Zhejiang University, Hangzhou, China
| | - Jing Hu
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
| | - Sitao Zhang
- National Institute of Biological Sciences,7 Science Park Road, Beijing, China
| | - Yajing Hao
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA, USA
- China National Center for Bioinformation, Beijing, China
- Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Dongyang Zhang
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, USA
| | - Hao Qian
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
| | - Dong Wang
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA, USA.
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, USA.
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA.
| | - Xiang-Dong Fu
- Westlake Laboratory of Life Sciences and Biomedicine, School of Life Sciences and School of Medicine, Westlake University, Hangzhou, Zhejiang, China.
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Abstract
In anaphase, any unresolved DNA entanglements between the segregating sister chromatids can give rise to chromatin bridges. To prevent genome instability, chromatin bridges must be resolved prior to cytokinesis. The SNF2 protein PICH has been proposed to play a direct role in this process through the remodeling of nucleosomes. However, direct evidence of nucleosome remodeling by PICH has remained elusive. Here, we present an in vitro single-molecule assay that mimics chromatin under tension, as is found in anaphase chromatin bridges. Applying a combination of dual-trap optical tweezers and fluorescence imaging of PICH and histones bound to a nucleosome-array construct, we show that PICH is a tension- and ATP-dependent nucleosome remodeler that facilitates nucleosome unwrapping and then subsequently slides remaining histones along the DNA. This work elucidates the role of PICH in chromatin-bridge dissolution, and might provide molecular insights into the mechanisms of related SNF2 proteins.
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Cui S, Walker JR, Batenburg NL, Zhu XD. Cockayne syndrome group B protein uses its DNA translocase activity to promote mitotic DNA synthesis. DNA Repair (Amst) 2022; 116:103354. [PMID: 35738143 DOI: 10.1016/j.dnarep.2022.103354] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 04/30/2022] [Accepted: 06/07/2022] [Indexed: 11/24/2022]
Abstract
Mitotic DNA synthesis, also known as MiDAS, has been suggested to be a form of RAD52-dependent break-induced replication (BIR) that repairs under-replicated DNA regions of the genome in mitosis prior to chromosome segregation. Cockayne syndrome group B (CSB) protein, a chromatin remodeler of the SNF2 family, has been implicated in RAD52-dependent BIR repair of stalled replication forks. However, whether CSB plays a role in MiDAS has not been characterized. Here, we report that CSB functions epistatically with RAD52 to promote MiDAS at common fragile sites in response to replication stress, and prevents genomic instability associated with defects in MiDAS. We show that CSB is dependent upon the conserved phenylalanine at position 796 (F796), which lies in the recently-reported pulling pin that is required for CSB's translocase activity, to mediate MiDAS, suggesting that CSB uses its DNA translocase activity to promote MiDAS. Structural analysis reveals that CSB shares with a subset of SNF2 family proteins a translocase regulatory region (TRR), which is important for CSB's function in MiDAS. We further demonstrate that phosphorylation of S1013 in the TRR regulates the function of CSB in MiDAS and restart of stalled forks but not in fork degradation in BRCA2-deficient cells and UV repair. Taken together, these results suggest that the DNA translocase activity of CSB in vivo is likely to be highly regulated by post-translational modification in a context-specific manner.
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Affiliation(s)
- Shixin Cui
- Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada
| | - John R Walker
- Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada
| | - Nicole L Batenburg
- Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada
| | - Xu-Dong Zhu
- Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
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Selvam K, Plummer DA, Mao P, Wyrick JJ. Set2 histone methyltransferase regulates transcription coupled-nucleotide excision repair in yeast. PLoS Genet 2022; 18:e1010085. [PMID: 35263330 PMCID: PMC8936446 DOI: 10.1371/journal.pgen.1010085] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Revised: 03/21/2022] [Accepted: 02/08/2022] [Indexed: 12/17/2022] Open
Abstract
Helix-distorting DNA lesions, including ultraviolet (UV) light-induced damage, are repaired by the global genomic-nucleotide excision repair (GG-NER) and transcription coupled-nucleotide excision repair (TC-NER) pathways. Previous studies have shown that histone post-translational modifications (PTMs) such as histone acetylation and methylation can promote GG-NER in chromatin. Whether histone PTMs also regulate the repair of DNA lesions by the TC-NER pathway in transcribed DNA is unknown. Here, we report that histone H3 K36 methylation (H3K36me) by the Set2 histone methyltransferase in yeast regulates TC-NER. Mutations in Set2 or H3K36 result in UV sensitivity that is epistatic with Rad26, the primary TC-NER factor in yeast, and cause a defect in the repair of UV damage across the yeast genome. We further show that mutations in Set2 or H3K36 in a GG-NER deficient strain (i.e., rad16Δ) partially rescue its UV sensitivity. Our data indicate that deletion of SET2 rescues UV sensitivity in a GG-NER deficient strain by activating cryptic antisense transcription, so that the non-transcribed strand (NTS) of yeast genes is repaired by TC-NER. These findings indicate that Set2 methylation of H3K36 establishes transcriptional asymmetry in repair by promoting canonical TC-NER of the transcribed strand (TS) and suppressing cryptic TC-NER of the NTS.
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Affiliation(s)
- Kathiresan Selvam
- School of Molecular Biosciences, Washington State University, Pullman, Washington, United States of America
| | - Dalton A. Plummer
- School of Molecular Biosciences, Washington State University, Pullman, Washington, United States of America
| | - Peng Mao
- Department of Internal Medicine, Program in Cellular and Molecular Oncology, University of New Mexico Comprehensive Cancer Center, Albuquerque, New Mexico, United States of America
| | - John J. Wyrick
- School of Molecular Biosciences, Washington State University, Pullman, Washington, United States of America
- Center for Reproductive Biology, Washington State University, Pullman, Washington, United States of America
- * E-mail:
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Yan C, Dodd T, Yu J, Leung B, Xu J, Oh J, Wang D, Ivanov I. Mechanism of Rad26-assisted rescue of stalled RNA polymerase II in transcription-coupled repair. Nat Commun 2021; 12:7001. [PMID: 34853308 PMCID: PMC8636621 DOI: 10.1038/s41467-021-27295-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 11/10/2021] [Indexed: 12/22/2022] Open
Abstract
Transcription-coupled repair is essential for the removal of DNA lesions from the transcribed genome. The pathway is initiated by CSB protein binding to stalled RNA polymerase II. Mutations impairing CSB function cause severe genetic disease. Yet, the ATP-dependent mechanism by which CSB powers RNA polymerase to bypass certain lesions while triggering excision of others is incompletely understood. Here we build structural models of RNA polymerase II bound to the yeast CSB ortholog Rad26 in nucleotide-free and bound states. This enables simulations and graph-theoretical analyses to define partitioning of this complex into dynamic communities and delineate how its structural elements function together to remodel DNA. We identify an allosteric pathway coupling motions of the Rad26 ATPase modules to changes in RNA polymerase and DNA to unveil a structural mechanism for CSB-assisted progression past less bulky lesions. Our models allow functional interpretation of the effects of Cockayne syndrome disease mutations.
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Affiliation(s)
- Chunli Yan
- grid.256304.60000 0004 1936 7400Department of Chemistry, Georgia State University, Atlanta, GA USA ,grid.256304.60000 0004 1936 7400Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA USA
| | - Thomas Dodd
- grid.256304.60000 0004 1936 7400Department of Chemistry, Georgia State University, Atlanta, GA USA ,grid.256304.60000 0004 1936 7400Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA USA
| | - Jina Yu
- grid.256304.60000 0004 1936 7400Department of Chemistry, Georgia State University, Atlanta, GA USA ,grid.256304.60000 0004 1936 7400Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA USA
| | - Bernice Leung
- grid.266100.30000 0001 2107 4242Division of Pharmaceutical Sciences, Skaggs School of Pharmacy & Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093 USA
| | - Jun Xu
- grid.266100.30000 0001 2107 4242Division of Pharmaceutical Sciences, Skaggs School of Pharmacy & Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093 USA
| | - Juntaek Oh
- grid.266100.30000 0001 2107 4242Division of Pharmaceutical Sciences, Skaggs School of Pharmacy & Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093 USA
| | - Dong Wang
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy & Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, 92093, USA. .,Department of Cellular & Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, CA, 92093, USA. .,Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, 92093, USA.
| | - Ivaylo Ivanov
- Department of Chemistry, Georgia State University, Atlanta, GA, USA. .,Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, USA.
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Ghit A. Immunofluorescence studies to dissect the impact of Cockayne syndrome A alterations on the protein interaction and cellular localization. J Genet Eng Biotechnol 2021; 19:88. [PMID: 34132928 PMCID: PMC8208330 DOI: 10.1186/s43141-021-00190-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 06/08/2021] [Indexed: 11/24/2022]
Abstract
Background Cockayne syndrome (CS), which was discovered by Alfred Cockayne nearly 75 years ago, is a rare autosomal recessive disorder characterized by growth failure, neurological dysfunction, premature aging, and other clinical features including microcephaly, ophthalmologic abnormalities, dental caries, and cutaneous photosensitivity. These alterations are caused by mutations in the CSA or CSB genes, both of which are involved in transcription-coupled nucleotide excision repair (TC-NER), the sub-pathway of NER that rapidly removes UV-induced DNA lesions which block the progression of the transcription machinery in the transcribed strand of active genes. Several studies assumed that CSA and CSB genes can play additional roles outside TC-NER, due to the wide variations in type and severity of the CS phenotype and the lack of a clear relationship between genotype and phenotype. To address this issue, our lab generated isogenic cell lines expressing wild type as well as different versions of mutated CSA proteins, fused at the C-terminus with the Flag and HA epitope tags (CSAFlag-HA). In unpublished data, the identity of the CSA-interacting proteins was determined by mass spectrometry. Among which three subunits (namely, CCT3, CCT8, and TCP1) of the TRiC/CCT complex appeared as novel interactors. TRiC is a chaperonin involved in the folding of newly synthesized or unfolded proteins. The aim of this study is directed to investigate by immunofluorescence analysis the impact of the selected CSA mutations on the subcellular localization of the CSA protein itself as well as on its novel interactors CCT3, CCT8, and TCP1. Results We showed that specific CSA mutations impair the proper cellular localization of the protein, but have no impact on the cellular distribution of the TRiC subunits or CSA/TRiC co-localization. Conclusion We suggested that the activity of the TRiC complex does not rely on the functionality of CSA. Supplementary Information The online version contains supplementary material available at 10.1186/s43141-021-00190-7.
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Affiliation(s)
- Amr Ghit
- Department of Biology and Biotechnology, University of Pavia, Pavia, Italy. .,Department of Biotechnology, Institute of Graduate Studies and Research (IGSR), Alexandria University, Alexandria, Egypt.
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Abstract
As primary carriers of epigenetic information and gatekeepers of genomic DNA, nucleosomes are essential for proper growth and development of all eukaryotic cells. Although they are intrinsically dynamic, nucleosomes are actively reorganized by ATP-dependent chromatin remodelers. Chromatin remodelers contain helicase-like ATPase motor domains that can translocate along DNA, and a long-standing question in the field is how this activity is used to reposition or slide nucleosomes. In addition to ratcheting along DNA like their helicase ancestors, remodeler ATPases appear to dictate specific alternating geometries of the DNA duplex, providing an unexpected means for moving DNA past the histone core. Emerging evidence supports twist-based mechanisms for ATP-driven repositioning of nucleosomes along DNA. In this review, we discuss core experimental findings and ideas that have shaped the view of how nucleosome sliding may be achieved.
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Affiliation(s)
- Ilana M Nodelman
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland 21218, USA;
| | - Gregory D Bowman
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland 21218, USA;
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Oh J, Xu J, Chong J, Wang D. Molecular basis of transcriptional pausing, stalling, and transcription-coupled repair initiation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2020; 1864:194659. [PMID: 33271312 DOI: 10.1016/j.bbagrm.2020.194659] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 11/21/2020] [Accepted: 11/23/2020] [Indexed: 12/24/2022]
Abstract
Transcription elongation by RNA polymerase II (Pol II) is constantly challenged by numerous types of obstacles that lead to transcriptional pausing or stalling. These obstacles include DNA lesions, DNA epigenetic modifications, DNA binding proteins, and non-B form DNA structures. In particular, lesion-induced prolonged transcriptional blockage or stalling leads to genome instability, cellular dysfunction, and cell death. Transcription-coupled nucleotide excision repair (TC-NER) pathway is the first line of defense that detects and repairs these transcription-blocking DNA lesions. In this review, we will first summarize the recent research progress toward understanding the molecular basis of transcriptional pausing and stalling by different kinds of obstacles. We will then discuss new insights into Pol II-mediated lesion recognition and the roles of CSB in TC-NER.
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Affiliation(s)
- Juntaek Oh
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy & Pharmaceutical Sciences; University of California, San Diego, La Jolla, CA 92093, United States
| | - Jun Xu
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy & Pharmaceutical Sciences; University of California, San Diego, La Jolla, CA 92093, United States
| | - Jenny Chong
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy & Pharmaceutical Sciences; University of California, San Diego, La Jolla, CA 92093, United States
| | - Dong Wang
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy & Pharmaceutical Sciences; University of California, San Diego, La Jolla, CA 92093, United States; Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, United States; Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, United States.
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Xu J, Wang W, Xu L, Chen JY, Chong J, Oh J, Leschziner AE, Fu XD, Wang D. Cockayne syndrome B protein acts as an ATP-dependent processivity factor that helps RNA polymerase II overcome nucleosome barriers. Proc Natl Acad Sci U S A 2020; 117:25486-25493. [PMID: 32989164 PMCID: PMC7568279 DOI: 10.1073/pnas.2013379117] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
While loss-of-function mutations in Cockayne syndrome group B protein (CSB) cause neurological diseases, this unique member of the SWI2/SNF2 family of chromatin remodelers has been broadly implicated in transcription elongation and transcription-coupled DNA damage repair, yet its mechanism remains largely elusive. Here, we use a reconstituted in vitro transcription system with purified polymerase II (Pol II) and Rad26, a yeast ortholog of CSB, to study the role of CSB in transcription elongation through nucleosome barriers. We show that CSB forms a stable complex with Pol II and acts as an ATP-dependent processivity factor that helps Pol II across a nucleosome barrier. This noncanonical mechanism is distinct from the canonical modes of chromatin remodelers that directly engage and remodel nucleosomes or transcription elongation factors that facilitate Pol II nucleosome bypass without hydrolyzing ATP. We propose a model where CSB facilitates gene expression by helping Pol II bypass chromatin obstacles while maintaining their structures.
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Affiliation(s)
- Jun Xu
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093
| | - Wei Wang
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093
| | - Liang Xu
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093
| | - Jia-Yu Chen
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92093
| | - Jenny Chong
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093
| | - Juntaek Oh
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093
| | - Andres E Leschziner
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92093
- Section of Molecular Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093
| | - Xiang-Dong Fu
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92093
| | - Dong Wang
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093;
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92093
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