Abstract
Transcription coupled nucleotide excision repair (TCR) is a major pathway responsible for removal of helix distorting DNA lesions from transcriptionally active regions of the genome. Rad26, a key factor of the TCR pathway, is known to play a role during early steps of TCR. Here, we show that Rad26-mediated TCR is not absolutely dependent on active transcription elongation in budding yeast. As per our results, RAD26-deleted cells show enhanced UV sensitivity compared to wild type cells under conditions where transcription elongation is inhibited. The increased UV sensitivity observed in RAD26-deleted cells, however, is not due to reduced expression of the major NER-responsive genes. Interestingly, transcription of the constitutively expressed RPB2 gene is adversely affected in RAD26-deleted cells during UV-induced DNA damage repair. In consonance, chromatin immunoprecipitation analysis showed that unlike in wild type, in RAD26-deleted cells no significant reduction in RNA polymerase II occupancy occurs during nucleotide excision repair in the transcriptionally active loci like, RPB2, PYK1 and RPL2B. These results collectively indicate that removal of RNAPII during DNA damage repair following UV irradiation is dependent on Rad26.
Highlights
Stability of the eukaryotic and prokaryotic genome is continually challenged by various exogenous and endogenous sources that can damage DNA
Sin mutants are Swi/Snf Independent mutants and repair studies have shown that the Sin mutant H4 R45H is more resistant to UV irradiations and have faster nucleotide excision repair rate compared to wild type cells [26]
We have earlier shown that Transcription coupled nucleotide excision repair (TCR) forms a major part of nucleotide excision repair (NER) in Sin (Swi/Snf-independent) mutant H4 R45H cells, which have a distinctly faster NER rate compared to wild type
Summary
Stability of the eukaryotic and prokaryotic genome is continually challenged by various exogenous and endogenous sources that can damage DNA. While damage recognition is known to be the rate-limiting step of NER, TCR is initiated when the RNA polymerase II complex stalls at a DNA lesion and the subsequent repair machinery acts rapidly to remove lesions from the transcribed strand [5,6,7,8]. On encountering CPD lesions the conformation of RNA Pol II does not change [10] Following such encounter of DNA damage with RNA Pol II, TCR requires an additional mechanism to render the DNA lesion accessible to the NER factors
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