ZDHHC20-mediated S-palmitoylation of KAP1/TRIM28 promotes DNA damage repair.

S-palmitoylation mediated by the zinc finger aspartate-histidine-histidine-cysteine (ZDHHC) protein acyltransferases (PATs) modulates protein localization, stability, interactions and signal transduction. In this study, we screened the 23 ZDHHC family members and identified ZDHHC20 as one of the major PATs involved in the DNA damage response (DDR). Inhibition of ZDHHC20 expression impaired cellular DNA damage repair capabilities. Meanwhile, data from ZDHHC20 knock-out mice, human tumor cell lines and xenograft tumor models showed that knock-out of ZDHHC20 significantly enhanced radiosensitivity. Using palmitoylation label-free quantitative proteomics, we found that over 600 proteins were palmitoylated in a ZDHHC20-dependent manner. Via the acyl-biotin exchange (ABE) assay, we revealed that KRAB-associated protein 1 (KAP1), also known as tripartite motif-containing protein 28 (Trim28), was palmitoylated at cysteine 232 by ZDHHC20. Notably, ZDHHC20-dependent KAP1 palmitoylation increased the chromatin binding of phosphorylated KAP1, which facilitated chromatin accessibility and subsequent recruitment of the DDR components BRCA1 and 53BP1. Further, we demonstrated that Ataxia-Telangiectasia Mutated (ATM)-dependent phosphorylation of ZDHHC20 at serine 339 increased KAP1 palmitoylation. Taken together, our findings elucidate the role and mechanism of the ATM-ZDHHC20-KAP1 axis in the DDR and provide a novel sensitizing strategy for radiotherapy and chemotherapy.