APLF is a forkhead associated (FHA)-containing protein with poly(ADP-ribose)-binding zinc finger (PBZ) domains, which undergoes ionizing radiaiton (IR)-induced and ATM-dependent phosphorylation at serine-116 (Ser116). Here we demonstrate that the phosphorylation of APLF at Ser116 in human U2OS cells by ATM is dependent on PARP3 levels and the APLF PBZ domains. The interaction of APLF at sites of DNA damage was diminished by the single substitution of APLF Ser116 to alanine, and the cellular depletion or chemical inhibition of ATM or PARP3 also altered the retention of APLF at sites of laser-induced DNA damage, and impaired the accumulation of Ser116-phosphorylated APLF at IR-induced γH2AX foci in human cells. The data further suggest that ATM and PARP3 participate in a common signaling pathway to facilitate APLF-Ser116 phosphorylation, which, in turn, appears to be required for efficient DNA double-strand break (DSB) repair kinetics and cell survival following IR. Collectively, these findings provide a more detailed understanding of the molecular pathway that leads to the phosphorylation of APLF following DNA damage, and suggest that Ser116-APLF phosphorylation facilitates APLF-dependent DSB repair.

Citation Format: Christine A. Koch, Amanda L. Fenton, Purnata Shirodkar, Li Meng. The PARP3- and ATM-dependent phosphorylation of APLF facilitates DNA double-strand break repair. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 623. doi:10.1158/1538-7445.AM2013-623