ATM mediates repression of DNA end-degradation in an ATP-dependent manner

作者：Rahal Elias A; Henricksen Leigh A; Li Yuling; Turchi John J; Pawelczak Katherine S; Dixon Kathleen^*

来源：DNA Repair, 2008, 7(3): 464-475.

DOI：10.1016/j.dnarep.2007.12.003

• ATM
• DNA degradation
• double-strand break repair
• microhomology-mediated end-joining
• PI-3-kinase-like kinases

Ataxia telangiectasia mutated (ATM) is a PI3-kinase-like kinase (PIKK) associated with DNA double-strand break (DSB) repair and cell cycle control. We have previously reported comparable efficiencies of DSB repair in nuclear extracts from both ATM deficient (A-T) and control (ATM(+)) cells; however, the repair products from the A-T nuclear extracts contained deletions encompassing longer stretches of DNA compared to controls. These deletions appeared to result from end-joining at sites of microhomology. These data suggest that ATM hinders error-prone repair pathways that depend on degradation of DNA ends at a break. Such degradation may account for the longer deletions we formerly observed in A-T cell extracts. To address this possibility we assessed the degradation of DNA duplex substrates in A-T and control nuclear extracts under DSB repair conditions. We observed a marked shift in signal intensity from full-length products to shorter products in A-T nuclear extracts, and addition of purified ATM to A-T nuclear extracts restored full-length product detection. This repression of degradation by ATM was both ATP-dependent and inhibited by the PIKK inhibitors wortmannin and caffeine. Addition of pre-phosphorylated ATM to an A-T nuclear extract in the presence of PIKK inhibitors was insufficient in repressing degradation, indicating that kinase activities are required. These results demonstrate a role for ATM in preventing the degradation of DNA ends possibly through repressing nucleases implicated in microhomology-mediated end-joining.

• 出版日期2008-3-1