title: Ubiquitin-specific protease 7 regulates nucleotide excision repair through deubiquitinating XPC protein and preventing XPC protein from undergoing ultraviolet light-induced and VCP/p97 protein-regulated proteolysis.
abstract: Ubiquitin specific protease 7 (USP7) is a known deubiquitinating enzyme for tumor suppressor p53 and its downstream regulator, E3 ubiquitin ligase Mdm2. Here we report that USP7 regulates nucleotide excision repair (NER) via deubiquitinating xeroderma pigmentosum complementation group C (XPC) protein, a critical damage recognition factor that binds to helix-distorting DNA lesions and initiates NER. XPC is ubiquitinated during the early stage of NER of UV light-induced DNA lesions. We demonstrate that transiently compromising cellular USP7 by siRNA and chemical inhibition leads to accumulation of ubiquitinated forms of XPC, whereas complete USP7 deficiency leads to rapid ubiquitin-mediated XPC degradation upon UV irradiation. We show that USP7 physically interacts with XPC in vitro and in vivo. Overexpression of wild-type USP7, but not its catalytically inactive or interaction-defective mutants, reduces the ubiquitinated forms of XPC. Importantly, USP7 efficiently deubiquitinates XPC-ubiquitin conjugates in deubiquitination assays in vitro. We further show that valosin-containing protein (VCP)/p97 is involved in UV light-induced XPC degradation in USP7-deficient cells. VCP/p97 is readily recruited to DNA damage sites and colocalizes with XPC. Chemical inhibition of the activity of VCP/p97 ATPase causes an increase in ubiquitinated XPC on DNA-damaged chromatin. Moreover, USP7 deficiency severely impairs the repair of cyclobutane pyrimidine dimers and, to a lesser extent, affects the repair of 6-4 photoproducts. Taken together, our findings uncovered an important role of USP7 in regulating NER via deubiquitinating XPC and by preventing its VCP/p97-regulated proteolysis.
authors.affiliation: Department of Radiology, The Ohio State University, Columbus, Ohio 43210.
authors.forename: Jinshan
authors.initials: J
authors.lastname: He
authors.affiliation: Department of Radiology, The Ohio State University, Columbus, Ohio 43210. Electronic address: zhu.49@osu.edu.
authors.forename: Qianzheng
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: Department of Radiology, The Ohio State University, Columbus, Ohio 43210.
authors.forename: Gulzar
authors.initials: G
authors.lastname: Wani
authors.affiliation: Department of Radiology, The Ohio State University, Columbus, Ohio 43210.
authors.forename: Nidhi
authors.initials: N
authors.lastname: Sharma
authors.affiliation: Department of Radiology, The Ohio State University, Columbus, Ohio 43210.
authors.forename: Chunhua
authors.initials: C
authors.lastname: Han
authors.affiliation: Department of Radiology, The Ohio State University, Columbus, Ohio 43210.
authors.forename: Jiang
authors.initials: J
authors.lastname: Qian
authors.affiliation: Department of Radiology, The Ohio State University, Columbus, Ohio 43210.
authors.forename: Kyle
authors.initials: K
authors.lastname: Pentz
authors.affiliation: Department of Radiology, The Ohio State University, Columbus, Ohio 43210.
authors.forename: Qi-En
authors.initials: QE
authors.lastname: Wang
authors.affiliation: Department of Radiology, The Ohio State University, Columbus, Ohio 43210; Department of Molecular and Cellular Biochemistry, and The Ohio State University, Columbus, Ohio 43210; James Cancer Hospital and Solove Research Institute, The Ohio State University, Columbus, Ohio 43210. Electronic address: wani.2@osu.edu.
authors.forename: Altaf A
authors.initials: AA
authors.lastname: Wani
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage; D004260:DNA Repair / Q000235:genetics / Q000528:radiation effects*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D009154:Mutation; D059748:Proteolysis / Q000528:radiation effects*; D011740:Pyrimidine Dimers / Q000235:genetics / Q000378:metabolism; D043222:Ubiquitin Thiolesterase / Q000235:genetics / Q000378:metabolism*; D000076084:Ubiquitin-Specific Peptidase 7; D054875:Ubiquitination / Q000235:genetics / Q000528:radiation effects*; D014466:Ultraviolet Rays; D000074405:Valosin Containing Protein
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D011740:Pyrimidine Dimers; C086984:XPC protein, human; C464569:USP7 protein, human; D043222:Ubiquitin Thiolesterase; D000076084:Ubiquitin-Specific Peptidase 7; D000251:Adenosine Triphosphatases; C000614178:VCP protein, human; D000074405:Valosin Containing Protein
keywords: DNA Damage Response; DNA Repair; Deubiquitylation (Deubiquitination); Nucleotide Excision Repair; Ubiquitin-specific Protease 7; Ubiquitylation (Ubiquitination); Valosin-containing Protein; Xeroderma Pigmentosum Complementation Group C Protein