Genome-wide distribution of Rad26 and Rad1-Rad10 reveals their relationship with Mediator and RNA polymerase II

Transcription is coupled with DNA repair, especially within nucleotide excision repair (NER). Mediator is a conserved coregulator playing a key role in RNA polymerase (Pol) II transcription. Mediator also links transcription and NER via a direct contact with Rad2/XPG endonuclease. In this work, we analyzed the genome-wide distribution of Rad26/CSB and that of Rad1-Rad10/XPF-ERCC1, addressing the question on a potential interplay of these proteins with Mediator and Pol II in yeast Saccharomyces cerevisiae. Our genome-wide analyses show that Rad1-Rad10 and Rad26 are present on the yeast genome in the absence of genotoxic stress, especially on highly transcribed regions, with Rad26 binding strongly correlating with that of Pol II. Moreover, we revealed that Rad1-Rad10 and Rad26 colocalize with Mediator on intergenic regions and physically interact with this complex. Using kin28 TFIIH mutant, we showed that Mediator stabilization on core promoters lead to an increase in Rad1-Rad10 chromatin binding, whereas Rad26 occupancy is less impacted by Mediator and follows mainly a decrease in Pol II transcription. Combined with multivariate analyses, our results reveal the interplay between Rad1-Rad10, Rad26, Mediator and Pol II, modulated by the binding dynamics of Mediator and Pol II transcription. In conclusion, we extend the Mediator link to Rad1-Rad10 and Rad26 NER proteins and reveal important differences in Mediator relationships with Rad2, Rad1-Rad10 and Rad26. Our work thus contributes to new concepts of the functional interplay between transcription and DNA repair, relevant for human diseases including cancer and XP/CS syndromes.