Inhibition of the action of Escherichia coli transcription termination protein ϱ by poly(C) and heparin

Abstract

Poly(C) and heparin at low concentrations (1 μg/ml) prevent the RNA synthesis termination protein ϱ from functioning during the biosynthesis of RNA from bacteriophage T7 DNA catalyzed by Escherichia coli RNA polymerase. Both of these polyanions inhibit the binding of ϱ to isolated T7 RNA. Heparin also inhibits ϱATPase when isolated RNA transcripts are used as cofactors. It is concluded that the polyanions inhibit termination by binding to the site on ϱ that is normally used for the initial interaction with a nascent RNA transcript in the ϱ-mediated release of RNA. Since one of the inhibitors, poly(C), is itself a potent activator for ϱATPase, it is also concluded that the ATP hydrolysis step that is required for ϱ termination has to be coupled to an action of ϱ on the RNA molecule to be released from the transcription complex.