Poly(ADP-ribose) polymerase (PARP)-1 may act in an error-prone pathway called alternative end joining (Alt-EJ) for DNA double-strand break (DSB) repair when nonhomologous end joining is defective. We examined the recruitment of PARP-1 to chromatin in response to radiomimetic agents and the effects of PARP-1 inhibition on DSB repair and recruitment of the meiotic recombination (MRE)-11-double-strand break repair (RAD50) protein-Nijmegen breakage syndrome (NSB)-1 (MRN) complex to the chromatin in Ku70-deficient breast cancer cells. The chromatin-binding affinity of PARP-1 was enhanced in response to neocarzinostatin (NCS) or calicheamicin treatment in the absence of Ku70. PARP-1 inhibition impaired the repair of both NCS-induced DSBs and intron-encoded endonuclease from Physarum polycephalum-induced site-specific DSB. Both fractionation and chromatin immunoprecipitation assays demonstrated that chromatin recruitment of MRN was PARP-1 dependent. These data suggest that PARP-1 is vital for DSB repair in breast cancer cells when Alt-EJ is activated.-Huang, Y., Shao, Q., Luo, X., Yang, D., Zeng, B., Xiang, T., Ren, G., Cheng, Q. Poly(ADP-ribose) polymerase-1 promotes recruitment of meiotic recombination-11 to chromatin and DNA double-strand break repair in Ku70-deficient breast cancer cells.
Keywords: Alt-EJ; MRN complex; NHEJ; PARP inhibition.