抄録
The genome as a carrier of genetic information in living cells is vulnerable to DNA-damaging agents of both endogenous and environmental origins. To remove DNA lesions, cells have two major repair pathways; nucleotide excision repair (NER) operating on bulky helix-distorting damage caused by environmental mutagens and base excision repair for non-bulky and non-helix-distorting DNA modifications caused by endogenous and some chemical carcinogen-induced damage. When RNA polymerase II in the elongation phase encounters DNA damage that blocks transcription, transcription-coupled repair (TCR), a specialized pathway that efficiently removes lesions on the transcribed strand, operates to counteract the immediate and cytotoxic response of the interference. The transcribed strand is repaired much faster by TCR than is the non-transcribed strand or inactive regions by global genome repair (GGR). The focus of this project is to investigate how the DNA lesion causes the stop of pol II during transcription elongation which is thought to be a trigger step of TCR. To analyze effect of DNA lesions on transcription elongation, purified pol II and oligo dC tailed template containing a DNA lesion were employed for transcription elongation assays. The results showed that pol II stalled at DNA lesions by incorporation of nucleotides and formed pol II/lesions/transcrips complexes. We discuss these observations together with the other properties of pol II and indicate that stalled-pol II itself has function as damage sensor.
