Abundance of BER-related proteins depends on cell proliferation status and the presence of DNA polymerase β

In mammalian cells,murine n-methylpurine dna glycosylase (mpg) removes bases damaged spontaneously or by chemical agents through the process called base excision repair (ber). in this study,we investigated the influence of pol β deficiency on mpg-initiated ber efficiency and the expression levels of ber-related proteins in log-phase and growth-arrested (g0) mouse embryonic fibroblasts (mefs). g0 wild-type (wt) or pol β-deficient (pol β-ko) cells showed greater resistance to methyl methanesulfonate than did log-phase cells,and repair of methylated bases was less efficient in the g0 cells. apex1 mrna expression was significantly lower in pol β-ko or g0 wt mefs than in log-phase wt mefs. moreover,although mpg mrna levels did not differ significantly among cell types,mpg protein levels were significantly higher in log-phase wt cells than in log-phase pol β-ko cells or either type of g0 cells. additionally,proliferating cell nuclear antigen protein levels were also reduced in log-phase pol β-ko cells or either type of g0 cells. these results indicated that mpg-initiated ber functions mainly in proliferating cells,but less so in g0 cells,and that pol β may be involved in regulation of the amount of intracellular repair proteins. © the author 2015.