Functionally distinct nucleosome-free regions in yeast require Rad7 and Rad16 for nucleotide excision repair

In yeast, Rad7 and Rad16 are two proteins required for nucleotide excision repair (NER) of non-transcribed chromatin. They have roles in damage recognition, in the postincision steps of NER, and in ultraviolet-light-dependent histone H3 acetylation. Moreover, Rad16 is an ATP-ase of the SNF2 superfamily and therefore might facilitate chromatin repair by nucleosome remodelling. Here, we used yeast rad7Δ rad16Δ mutants and show that Rad7–Rad16 is also required for NER of UV-lesions in three functionally distinct nucleosome-free regions (NFRs), the promoter and 3′-end of the URA3 gene and the ARS1 origin of replication. Moreover, rapid repair of UV-lesions by photolyase confirmed that nucleosomes were absent and that neither UV-damage formation nor rad7Δ rad16Δ mutations altered chromatin accessibility in NFRs. The data are consistent with a role of Rad7–Rad16 in damage recognition and processing in absence of nucleosomes. An additional role in nucleosome remodelling is discussed.