科研之友
微信
新浪微博
Facebook
分享链接
摘要
The process of base excision repair (BER) recognizes and repairs small lesions or inappropriate bases on DNA through either a short-patch or long-patch pathway. The enzymes involved in BER have been well-characterized on DNA substrates, and, somewhat surprisingly, many of these enzymes, including several DNA glycosylases, AP endonuclease (APE), FEN1 endonuclease, and DNA ligases, have been shown to have activity on DNA substrates within nucleosomes. DNA polymerase beta (Pol beta), however, exhibits drastically reduced or no activity on nucleosomal DNA. Interestingly, acetylation of Pol beta, by the acetyltransferase p300, inhibits its 5' dRP-lyase activity and presumably pushes repair of DNA substrates through the long-patch base excision repair (LP-BER) pathway. In addition to the major enzymes involved in BER, a chromatin architectural factor, HMGB1, was found to directly interact with and enhance the activity of APE1 and FEN1, and thus may aid in altering the structure of the nucleosome to be more accessible to BER factors. In this work, we investigated whether acetylation of Pol beta, either alone or in conjunction with HMGB1, facilitates its activity on nucleosome substrates. We find acetylated Pol beta exhibits enhanced strand displacement synthesis activity on DNA substrates, but, similar to the unmodified enzyme, has little or no activity on nucleosomes. Preincubation of DNA templates with HMGB1 has little or no stimulatory effect on Pol beta and even is inhibitory at higher concentrations. In contrast, preincubation of nucleosomes with HMGB1 rescues Pol beta gap-filling activity in nucleosomes, suggesting that this factor may help overcome the repressive effects of chromatin.
- 出版日期2017-1-31
