Nus A protein affects transcriptional pausing and termination in vitro by binding to different sites on the transcription complex.
We examined the in vitro concentration dependence of the effects of Nus A on transcription termination and pausing to determine if Nus A affects both pausing and termination in vitro by binding to a single site on the transcription complex. Nus A was shown to cause maximal increases of pausing at a concentration approximately equimolar to RNA polymerase. However, the effects of Nus A on termination require much higher Nus A concentrations than are required for pausing. It is therefore likely that the effects of Nus A on pausing and termination result from the binding of Nus A to different sites on the transcription complex. Since proteins that probably bind RNA nonspecifically were also shown to strongly reduce termination at a Rho-dependent terminator, Nus A may decrease Rho-dependent termination by binding nonspecifically to RNA. This proposal is consistent with most of the available data on the in vitro effects of Nus A and provides a mechanistic basis for previously unexplained details of Nus A caused decreases in Rho-dependent termination. We further speculate that most or all of the in vivo roles of Nus A may involve the enhancement of pausing.
Sigmund
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CD
Department of Experimental Biology, Roswell Park Memorial Institute, Buffalo, New York 14263.
Morgan
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EA
D001426:Bacterial Proteins / Q000502:physiology*; D004926:Escherichia coli / Q000235:genetics; D005809:Genes, Regulator; D066298:In Vitro Techniques; D012234:Rho Factor / Q000502:physiology; D013728:Terminator Regions, Genetic; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D012234:Rho Factor; D014157:Transcription Factors