Maspin increases Ku70 acetylation and Bax-mediated cell death in cancer cells.

Ku70, a DNA repair protein, was recently identified as a critical anti-apoptotic protein that inhibits Bax translocation to mitochondria. The dissociation of Bax from Ku70 is essential for the apoptotic activity of Bax. Here, we show that maspin, a tumor suppressor protein frequently lost in cancer, regulates this process. Maspin increased cell death in a Ku70 acetylation-dependent manner. Maspin inhibited histone deacetylase 1 (HDAC1) and thus increased the acetylation of Ku70 and the dissociation of Bax from Ku70, which led to the induction of apoptosis. These results reveal maspin as a Ku70-interacting molecule and provide the basis for a new endogenous acetylation-based control mechanism that reduces Ku70-mediated sequestration of Bax from mitochondria.