THE YEAST RAD7 AND RAD16 GENES ARE REQUIRED FOR POSTINCISION EVENTS DURING NUCLEOTIDE EXCISION-REPAIR - IN-VITRO AND IN-VIVO STUDIES WITH RAD7 AND RAD16 MUTANTS AND PURIFICATION OF A RAD7 RAD16-CONTAINING PROTEIN COMPLEX/

In eukaryotes, nucleotide excision repair (NER) is a complex reaction requiring multiple proteins. In the yeast Saccharomyces cerevisiae, tw o of these proteins, Rad7 and Rad16, are specifically involved in the removal of lesions from transcriptionally silent regions of the genome in vivo, Extracts prepared from rad7 or rad16 mutant cells are defici ent, but not totally defective, in both oligonucleotide excision and r epair synthesis of damaged plasmid DNA, We show that these extracts ar e, however, fully proficient in the incision step of the NER reaction in vitro. Furthermore, using a cdcs mutant to trap incision intermedia tes, we demonstrate that rad7 and rad16 mutants are proficient in NER- dependent DNA incision in vivo, A purified protein complex containing both Rad7 and Rad16 proteins complements the oligonucleotide excision and repair synthesis defects in rad7 and rad16 mutant extracts. We con clude that the products of the RAD7 and RAD16 genes are involved in a postincision event(s) during NER in yeast.