Identification of KIN (KIN17), a human gene encoding a nuclear DNA-binding protein, as a novel component of the TP53-independent response to ionizing radiation.

Ionizing radiation elicits a genetic response in human cells that allows cell survival. The human KIN (also known as KIN17) gene encodes a 45-kDa nuclear DNA-binding protein that participates in the response to UVC radiation and is immunologically related to the bacterial RecA protein. We report for the first time that ionizing radiation and bleomycin, a radiomimetic drug, which produce single- and double-strand breaks, increased expression of KIN in human cells established from tumors, including MeWo melanoma, MCF7 breast adenocarcinoma, and ATM+ GM3657 lymphoblast cells. KIN expression increased rapidly in a dose-dependent manner after irradiation. Under the same conditions, several genes controlled by TP53 were induced with kinetics similar to that of KIN. Using the CDKN1A gene as a marker of TP53 responsiveness, we analyzed the up-regulation of KIN and showed that is independent of the status of TP53 and ATM. In contrast, the presence of a dominant mutant for activating transcription factor 2 (ATF2) completely abolished the up-regulation of KIN. Our results suggest a role for ATF2 in the TP53-independent increase in KIN expression after gamma irradiation.