Helicobacter pylori virulence factor vacuolating cytotoxin A (VacA) promotes homologous recombination repair in GES-1 cells

Abstract

Objective To analyze the impact of Helicobacter pylori standard strain (Hp P12) and its virulence factor vacuolating cytotoxin A (VacA) on DNA damage and homologous recombination (HR) repair in a human gastric epithelial cell line (GES-1). Methods Strains of Hp P12 and vacA gene knockout Hp P12 (Hp P12 ΔvacA) were respectively used to infect GES-1 cells at a multiplicity of infection of 100. GES-1 cells treated with etoposide (50 μmol/L) or mitomycin (0.5 μg/ml) for 2 h were used as positive control. Western blot and immunofluorescence were performed to detect the expression of DNA damage marker protein γH2AX and key HR repair proteins (Rad51, pMRE11, CtIP and pCtIP) and the recruitment of them at DNA damage sites. Human embryonic kidney HEK-293 (DR-GFP) cells were infected with Hp P12 and Hp P12 ΔvacA strains to verify the impact of VacA on HR repair efficiency. Results The expression and recruitment of γH2AX and key HR repair proteins (Rad51, pMRE11, CtIP and pCtIP) were increased in Hp P12-infected cells as compared with that in uninfected and Hp P12 ΔvacA-infected cells (all P<0.05). To evaluate the HR repair efficiency, I-SceⅠ plasmid-transfected HEK-293 (DR-GFP) cells were infected with Hp P12 and Hp P12 ΔvacA and the results showed that green fluorescent protein (GFP)-positive cells were decreased after infection, especially in Hp P12 ΔvacA-infected cells (both P<0.05). Conclusions Hp P12 infection could cause DNA damage and promote HR repair in GES-1 cells, in which the virulence factor VacA played an important role. Key words: Helicobacter pylori; Homologous recombination repair; GES-1 cell; Vacuolating cytotoxin A (VacA)