The helicase of TFIIH hydrolyzes the β-γ bond of ATP to catalyze open complex formation at Pol II promoters. ATP hydrolysis is also required by a step subsequent to transcription initiation, most likely promoter clearance. Transcriptional activation by TFIIH was assayed on linear and circular templates either in the presence of ATP and GTP or the nonhydrolyzable nucleotide analogs AMP-PNP and GMP-PNP with RNA Polymerase I. The following results were obtained. Choose plausible explanation for these results. A. ATP is required under conditions where TFIIH is indispensable for initiation. These conditions include transcription from promoters containing a short stretch of mismatched base pairs surrounding the transcriptional start site as well as on negatively supercoiled templates. B. As Pol I transcription on linear templates requires neither ATP hydrolysis nor protein phosphorylation C. in contrast to Pol II, the topology of the template does not affect the requirement for TFIIH and neither the ATPase, helicase, nor protein kinase activity of TFIIH are required for Pol I transcription activation. -triyambak.org