TFIIH action in transcription initiation and promoter escape requires distinct regions of downstream promoter DNA

TFIIH is a multifunctional RNA polymerase II general initiation factor that includes two DNA helicases encoded by the Xeroderma pigmentosum complement ation group B (XPB) and D (XPD) genes and a cyclin-dependent protein kinase encoded by the CDK7 gene. Previous studies have shown that the TFIIH XPB D NA helicase plays critical roles not only in transcription initiation, wher e it catalyzes ATP-dependent formation of the open complex, but also in eff icient promoter escape, where it suppresses arrest of very early RNA polyme rase II elongation intermediates. In this report, we present evidence that ATP-dependent TFIIH action in transcription initiation and promoter escape requires distinct regions of the DNA template; these regions are well separ ated from the promoter region unwound by the XPB DNA helicase and extend, r espectively, approximate to 23-39 and approximate to 39-50 bp downstream fr om the transcriptional start site. Taken together, our findings bring to li ght a role for promoter DNA in TFIIH action and are consistent with the mod el that TFIIH translocates along promoter DNA ahead of the RNA polymerase I I elongation complex until polymerase has escaped the promoter.