Objective    To investigate the recruitment of base excision repair (BER) key factors

poly(ADP-ribose) polymerase 1 (PARP1)

ligase 3 and X-ray repair cross-complementing protein 1 (XRCC1) at chromatin with DNA double-strand break (DSB) after silencing Ku70

and the effect of PARP1 inhibition on the protein recruitment.     Methods    A cell line capable of inductively expressing Ku70 shRNA was treated with calicheamicin to induce DSB. Proteins recruited at the damaged chromatin after down-regulation of Ku70 expression were identified through stable isotope labeling by amino acids in cell culture (SILAC) and Western blotting

and the influence of PARP1 inhibitor

1

5-dihydroxyisoquinolin (DIQ)

on the protein recruitment was analyzed.     Results    Ku70 was down-regulated significantly by virtue of doxycycline

while the expression of other proteins was not influenced. The SILAC and Western blotting results showed that the recruitment of PARP1

ligase 3 and XRCC1 at the damaged chromatin increased after Ku70 down-regulation

and the recruitment of PARP1

ligase 3 and XRCC1 at the damaged chromatin increased with the increase of DSB degree. The recruitment of ligase 3 at the damaged chromatin decreased when the DIQ concentration increased.     Conclusion    Silencing Ku70 promotes the recruitment of PARP1

ligase 3 and XRCC1 at chromatin with DSB

and the protein recruitment is correlated positively to DSB degree. The recruitment of ligase 3 depends on PARP1 to some extent.