ATPase activity required for termination of transcription by the Escherichia coli protein factor rho

Abstract

The relationship between the RNA-dependent beta-gamma ATPase in purified rho preparations and rho-mediated termination of transcription has been investigated. In a purified in vitro system, transcription from lambdagal DNA has been carried out using either ribonucleoside triphosphates (NTPs) or four ribonucleoside 5'-(beta-gamma-imino)triphosphates (NMP-P(NH)Ps) as RNA precursors. In the presence of NTPs, rho termination activity results in (a) the synthesis of rho-dependent transcripts which are of discrete size by polyacrylamide gel analysis and (b) a marked reduction by hybridization assay in RNA transcribed distal to the rho-sensitive termination site tR. In the presence of four NMP-P(NH)Ps, which are not substrates for the beta-gamma ATPase, termination by rho is completely abolished, whereas rho-independent termination occurs normally. Addition of ATP to transcription reactions containing four NMP-P(NH)Ps restores termination, ruling out the possibility that the termination activity of rho is nonspecifically inhibited by the analog preparations. We interpret our data as strongly suggesting that the RNA-dependent beta-gamma ATPase activity of rho is required for rho-mediated termination of transcription.