Abstract
There are multiple pathways of DNA repairs. Short patch BER, a pathway to repair many damaged bases, is initiated by damage-pecific DNA glycosylase that removes the damaged base. The arising apurinic/apyrimidinic site (AP site) is recognized by AP endonuclease (APE) that incises the phosphodiester bond 5' next to the AP site, followed by addition of one nucleotide to the 3'-OH end of the incised AP site and excision of the 5'-deoxyribosephosphate by DNA polymerase β (pol β). Finally, DNA ligase completes repair by sealing the DNA ends. XRCC1 has no known enzymatic activity and is thought to act as a scaffold protein of this pathway. We have shown that methylpurine glycosylase (MPG) interacts with APE, APE interacts with pol β, and that DNA glycosylase activities are reduced in pol β deficient cell.
In this study, we examined the effect of APE and pol β on MPG activity under single-turnover condition, where the numbers of oligodeoxyribonucleotides including Hypoxanthine and MPG molecules are nearly equal. About 1.53- and 1.43-fold higher of MPG enzymatic activity was observed in the presence of APE and pol &beta, respectively. Moreover, in the presence of both APE and pol β, MPG activity was more significantly enhanced than in the presence of either APE or pol β. These data indicate the possibility that pol β directly influences enzymatic activity of MPG.
