USP39 promotes non-homologous end-joining repair by poly(ADP-ribose)-induced liquid demixing
Jae Jin Kim, Seo Yun Lee, Yiseul Hwang, Soyeon Kim, Jee Min Chung, Sangwook Park, Junghyun Yoon, Hansol Yun, Jae‐Hoon Ji, Sunyoung Chae, Hyeseong Cho, Chan Gil Kim, Ted M. Dawson, Hongtae Kim, Valina L. Dawson, Ho Chul Kang
Abstract
Mutual crosstalk among poly(ADP-ribose) (PAR), activated PAR polymerase 1 (PARP1) metabolites, and DNA repair machinery has emerged as a key regulatory mechanism of the DNA damage response (DDR). However, there is no conclusive evidence of how PAR precisely controls DDR. Herein, six deubiquitinating enzymes (DUBs) associated with PAR-coupled DDR were identified, and the role of USP39, an inactive DUB involved in spliceosome assembly, was characterized. USP39 rapidly localizes to DNA lesions in a PAR-dependent manner, where it regulates non-homologous end-joining (NHEJ) via a tripartite RG motif located in the N-terminus comprising 46 amino acids (N46). Furthermore, USP39 acts as a molecular trigger for liquid demixing in a PAR-coupled N46-dependent manner, thereby directly interacting with the XRCC4/LIG4 complex during NHEJ. In parallel, the USP39-associated spliceosome complex controls homologous recombination repair in a PAR-independent manner. These findings provide mechanistic insights into how PAR chains precisely control DNA repair processes in the DDR.