Multiple ATP-dependent steps in RNA polymerase II promoter melting and initiation.

Permanganate probing and abortive initiation assays were used to investigate the role of ATP in several successive stages of transcription initiation at the activated adeno E4 and mouse DHFR promoters. Removal of ATP at several points along the multi-step pathway blocked further progress towards its completion. Most strikingly, even if the DNA transcription start site is opened using ATP, the subsequent removal of ATP disallows formation of the first phosphodiester bond of the RNA. After ATP-dependent formation of a short RNA, a new transcription complex forms, which is more stable and has a longer open region. Both RNA and ATP appear to play roles in the formation of this complex. The need for ATP throughout this multi-step initiation pathway leads to new and unexpected possibilities for the use of energy and ATPases in transcription initiation.