Abstract 5365: Cdt2-mediated XPG degradation promotes DNA repair synthesis following DNA damage excision in nucleotide excision repair

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Xeroderma pigmentosum group G (XPG) protein is a structure-specific repair endonuclease, which cleaves DNA strands on the 3′ side of the DNA damage during nucleotide excision repair (NER). In addition, XPG plays a crucial role in initiating DNA repair synthesis through recruitment of PCNA to the repair sites. However, the fate of XPG protein subsequent to the excision of DNA damage has remained unresolved. Here, we show that XPG is degraded through proteasome-mediated proteolysis upon induction of bulky lesions from exposures to UV irradiation and cisplatin. NER process is required for XPG degradation because both UV and cisplatin treatment-induced XPG degradation is compromised in NER-deficient XP-A, XP-B, XP-C, and XP-F cells. In addition, the NER-related XPG degradation requires Cdt2, a component of an E3 ubiquitin ligase, CRL4Cdt2. Micropore local UV irradiation and in situ Proximity Ligation assays demonstrated that Cdt2 is recruited to the UV-damage sites and interacts with XPG in the presence of PCNA. Importantly, Cdt2-mediated XPG degradation is crucial to the subsequent recruitment of DNA polymerase δ and DNA repair synthesis. Collectively, our data supports the idea of PCNA recruitment to damage sites in conjunction with XPG, recognition of the PCNA-bound XPG by CRL4Cdt2 for specific ubiquitylation and protein degradation. Thus, XPG removal clears the space needed at the damage site for the subsequent recruitment of DNA pol δ and initiation of DNA synthesis. (This work was supported by grants from NIH). Note: This abstract was not presented at the meeting. Citation Format: Chunhua Han, Ran Zhao, Jiang Qian, Nidhi Sharma, Gulzar Wani, Jinshan He, Qianzheng Zhu, Qi-En Wang, Altaf A. Wani. Cdt2-mediated XPG degradation promotes DNA repair synthesis following DNA damage excision in nucleotide excision repair. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5365. doi:10.1158/1538-7445.AM2014-5365