RESUMEN
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.
Asunto(s)
Adenosina Trifosfatasas/metabolismo , Proteínas de Ciclo Celular/metabolismo , Reparación del ADN/efectos de la radiación , Proteínas de Unión al ADN/metabolismo , Proteolisis/efectos de la radiación , Ubiquitina Tiolesterasa/metabolismo , Ubiquitinación/efectos de la radiación , Rayos Ultravioleta , Adenosina Trifosfatasas/genética , Proteínas de Ciclo Celular/genética , Daño del ADN , Reparación del ADN/genética , Proteínas de Unión al ADN/genética , Células HeLa , Humanos , Mutación , Dímeros de Pirimidina/genética , Dímeros de Pirimidina/metabolismo , Ubiquitina Tiolesterasa/genética , Peptidasa Específica de Ubiquitina 7 , Ubiquitinación/genética , Proteína que Contiene ValosinaRESUMEN
CASE: Protein S deficiency, a hypercoagulable thrombophilia, often results in venous thromboembolism. Nontraumatic compartment syndrome in a patient with protein S deficiency has not been well publicized. Herein, we present a rare case of nontraumatic compartment syndrome of the hand and the thigh in a 48-year-old woman with a known history of protein S deficiency; emergency fasciotomies were needed. CONCLUSION: Based on our patient and a review of the current literature, we advocate for a heightened awareness of compartment syndrome in patients with protein S deficiency.