YEAST RNA-POLYMERASE-II TRANSCRIPTION IN-VITRO IS INHIBITED IN THE PRESENCE OF NUCLEOTIDE EXCISION-REPAIR - COMPLEMENTATION OF INHIBITION BY HOLO-TFIIH AND REQUIREMENT FOR RAD26

The Saccharomyces cerevisiae transcription factor IIH (TFIIH) is essen tial both for transcription by RNA polymerase II (RNAP II) and for nuc leotide excision repair (NER) of damaged DNA we have established cell extracts which support RNAP II transcription from the yeast CYC1 promo ter or NER of transcriptionally silent damaged DNA on independent plas mid templates and substrates. When plasmid templates and substrates fo r both processes are simultaneously incubated with these extracts, tra nscription is significantly inhibited. This inhibition is strictly dep endent on active NER and can be complemented with purified holo-TFIIH. These results suggest that in the presence of active NER, TFIIH is pr eferentially mobilized from the basal transcription machinery for use in NER. Inhibition of transcription in the presence of active NER requ ires the RAD26 gene, the yeast homolog of the human Cockayne syndrome group B gene (CSB).