Repair of 8-oxoguanine and Ogg1-incised apurinic sites in a CHO cell line.

The repair mechanisms involved in the removal of 8-oxo-7,8-dihydroguanine (8-oxoG) in damaged DNA have been investigated using cell-free extracts or purified proteins. However, in vivo repair assays are required to further dissect mechanisms involved in the repair of 8-oxoG in the cellular context. In this study, we analyzed the removal of 8-oxoG from plasmids that contain a single 8-oxoG.C base pair in a sequence that can be transcribed (TS) or nontranscribed (NTS) in a chinese hamster ovary (CHO) cell line. The results show that 8-oxoG located in a TS is removed faster than in a NTS, indicating transcription-coupled repair (TCR) of 8-oxoG in rodent cells. The results also show that CHO cells efficiently repair DNA molecules that contain an Ogg1-incised AP site, which is the first intermediate in the course of base excision repair of 8-oxoG.