Abstract
We investigated the effects of oxidative DNA lesion on transcription elongation by pol II using an oligo(dC)-tailed templates with a oxidative DNA lesion on the transcribed strand such as an 2-hydroxyadenie (2-OH A), 8-oxoadenine (8-oxoA), 8-oxoguanine (8-oxoG) or thymine glycorl (Tg). The results showed that pol II stalled at all types of oxidative DNA lesions. This indicates that pol II by itself stalls at the non-bulky and non-helix-distorting lesions without any factors.
Next, we purified TFIIS (SII) which is a transcription elongation factor that binds and assists pol II to stimulate the transcription elongation, and performed transcription elongation assays using oligo(dC)-tailed templates with an oxidative DNA lesion and the SII. Interestingly, there is no blockage of transcription elongation by pol II at 8-oxoG lesions in the presence of SII, while there is the blockage at 2-OH A, 8-oxoA or Tg lesions. It is suggested that polII with SII bypasses 8-oxoG lesions.
From these findings, here we propose two possible models for avoiding effects of oxidative DNA lesions. First, oxidative DNA lesions are subject to repair by the TCR pathway. Second, genes containing 8-oxoG lesions are transcribed by polII in the presence of SII.
