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

Elias A. Rahal, Leigh A. Henricksen, Yuling Li, John J. Turchi, Katherine S. Pawelczak, Kathleen Dixon

Research output: Contribution to journalArticle

12 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)464-475
Number of pages12
JournalDNA Repair
Issue number3
StatePublished - Mar 1 2008


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

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology

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    Rahal, E. A., Henricksen, L. A., Li, Y., Turchi, J. J., Pawelczak, K. S., & Dixon, K. (2008). ATM mediates repression of DNA end-degradation in an ATP-dependent manner. DNA Repair, 7(3), 464-475.