title: Modulation of nucleotide excision repair by mammalian SWI/SNF chromatin-remodeling complex.
abstract: Accessibility within chromatin is an important factor in the prompt removal of UV-induced DNA damage by nucleotide excision repair (NER). Chromatin remodeling by the SWI/SNF complex has been shown to play an important modulating role in NER in vitro and yeast in vivo. Nevertheless, the molecular basis of cross-talk between SWI/SNF and NER in mammalian cells is not fully understood. Here, we show that knockdown of Brg1, the ATPase subunit of SWI/SNF, negatively affects the elimination of cyclobutane pyrimidine dimers (CPD), but not of pyrimidine (6, 4)pyrimidone photoproducts (6-4PP) following UV irradiation of mammalian cells. Brg1-deficient cells exhibit a lower chromatin relaxation as well as impaired recruitment of downstream NER factors, XPG and PCNA, to UV lesions. However, the assembly of upstream NER factors, DDB2 and XPC, at the damage site was unaffected by Brg1 knockdown. Interestingly, Brg1 interacts with XPC within chromatin and is recruited to UV-damaged sites in a DDB2- and XPC-dependent manner. Also, postirradiation decrease of XPC levels occurred more rapidly in Brg1-deficient than normal cells. Conversely, XPC transcription remained unaltered upon Brg1 knockdown indicating that Brg1 affects the stability of XPC protein following irradiation. Thus, Brg1 facilitates different stages of NER by initially modulating UV-induced chromatin relaxation and stabilizing XPC at the damage sites, and subsequently stimulating the recruitment of XPG and PCNA to successfully culminate the repair.
authors.affiliation: Department of Radiology, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Qun
authors.initials: Q
authors.lastname: Zhao
authors.forename: Qi-En
authors.initials: QE
authors.lastname: Wang
authors.forename: Alo
authors.initials: A
authors.lastname: Ray
authors.forename: Gulzar
authors.initials: G
authors.lastname: Wani
authors.forename: Chunhua
authors.initials: C
authors.lastname: Han
authors.forename: Keisha
authors.initials: K
authors.lastname: Milum
authors.forename: Altaf A
authors.initials: AA
authors.lastname: Wani
mesh_terms: D002460:Cell Line; D042002:Chromatin Assembly and Disassembly; D002868:Chromosomal Proteins, Non-Histone / Q000502:physiology; D004249:DNA Damage; D004265:DNA Helicases / Q000502:physiology*; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004720:Endonucleases / Q000378:metabolism*; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism* / Q000502:physiology*; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism*; D021381:Protein Transport; D011740:Pyrimidine Dimers / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism* / Q000502:physiology*; D014466:Ultraviolet Rays / Q000009:adverse effects; D000099250:DNA Excision Repair Protein ERCC-5
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D004265:DNA Helicases; D004268:DNA-Binding Proteins; D004720:Endonucleases; D009687:Nuclear Proteins; D018809:Proliferating Cell Nuclear Antigen; D011740:Pyrimidine Dimers; D014157:Transcription Factors; D000099250:DNA Excision Repair Protein ERCC-5; C445179:SWI-SNF-B chromatin-remodeling complex; C086984:XPC protein, human; C084108:SMARCA4 protein, human