XRCC1 deficiency increased the DNA damage induced by γ-ray in HepG2 cell: Involvement of DSB repair and cell cycle arrest

Abstract

γ-ray irradiation can induce DNA damages which include base damages, single-strand breaks and double-strand breaks in various type cells. The DNA repair protein XRCC1, as a part of the BER pathway, forms complexes with DNA polymerase beta, DNA ligase III and poly-ADP-ribose polymerase (PARP) in the repair of DNA single strand breaks and also affects the repair of double strand breaks. However, it is still not known well whether XRCC1 contributes to affect the irradiation sensitivity and DNA damage in HepG2 cell and the potential mechanism. Hence, the purpose of this study was to explore whether abrogation of XRCC1 gene expression by shRNA could reduce DNA repair and thus sensitize HepG2 cells to γ-ray. Cell viability was measured by Trypan blue staining and cloning efficiency assay. The DNA damage was detected by Comet assay. Apoptosis and cell cycle were detected by flow cytometry. The DNA-PKcs and gadd153 mRNA expression were determined by Real-time PCR. Our results showed that abrogation of XRCC 1 could sensitize HepG2 cells to γ-ray. This enhanced sensitivity could be attributed to the increased DNA damage and increased cell cycle arrest, which might be related with the increasing of DNA-PKcs and gadd153 mRNA expression. Therefore, our results suggested that the γ-ray irradiation sensitivity could be increased by targeting inhibition of XRCC1 in HepG2 cell.

Keywords: BER; DNA damage; DNA repair; DNA-PKcs; DNA-dependent protein kinase catalytic subunit; DSB; DSBR; Hepatocellular carcinoma cells; OTM; SSB; SSBR; X-ray repair cross-complementing gene 1; XRCC1; XRCC1 gene; base excision repair; double strand break; double strand break repair; gadd153; growth arrest and DNA damage-inducible gene 153; olive tail moment; shRNA; short hairpin RNA; single strand break; single strand break repair.; γ-ray irradiation.