A role for ATP hydrolysis in vaccinia virus early gene transcription. Dissociation of the early transcription factor-promoter complex.

Vaccinia virus RNA polymerase requires the vaccinia early transcription factor, VETF, for the in vitro initiation of transcription at early gene promoters in a reaction requiring ATP hydrolysis. VETF binds specifically to early gene promoters and has an associated DNA-dependent ATPase activity. The effect of ATP on the interaction of VETF with the promoter for the vaccinia growth factor gene promoter has been examined. ATP had no marked effect on the steady-state level of promoter binding but dramatically affected the kinetics of dissociation of VETF from the promoter. The half-life of the VETF-promoter complex was greatly reduced in the presence of ATP. The destabilization of the complex was specific for ATP and dATP, consistent with the substrate specificity of the VETF-associated ATPase. ADP or the non-hydrolyzable ATP analog adenylyl-imidodiphosphate did not destabilize the complex suggesting that ATP hydrolysis is obligatory for dissociation. These findings provide a link between the promoter binding and ATPase activities associated with VETF and suggest that the ATP-dependent dissociation of the VETF-promoter complex is an important event in the transcription of vaccinia virus early genes.