DNA-dependent protein kinase promotes DNA end processing by MRN and CtIP
Rajashree A. Deshpande, Logan R. Myler, Michael M. Soniat, Nodar Makharashvili, Linda Lee, Susan P. Lees‐Miller, Ilya J. Finkelstein, Tanya T. Paull
Abstract
The repair of DNA double-strand breaks occurs through nonhomologous end joining or homologous recombination in vertebrate cells-a choice that is thought to be decided by a competition between DNA-dependent protein kinase (DNA-PK) and the Mre11/Rad50/Nbs1 (MRN) complex but is not well understood. Using ensemble biochemistry and single-molecule approaches, here, we show that the MRN complex is dependent on DNA-PK and phosphorylated CtIP to perform efficient processing and resection of DNA ends in physiological conditions, thus eliminating the competition model. Endonucleolytic removal of DNA-PK-bound DNA ends is also observed at double-strand break sites in human cells. The involvement of DNA-PK in MRN-mediated end processing promotes an efficient and sequential transition from nonhomologous end joining to homologous recombination by facilitating DNA-PK removal.