Abstract
The genes for the beta (rpoB) and beta' (rpoC) subunits of Escherichia coli RNA polymerase are the distal members of a complex transcriptional unit that contains four upstream ribosomal protein genes. The RNA polymerase subunit genes are transcribed at a lower frequency than the ribosomal protein genes as a result of termination at an attenuator preceding rpoB. A purified in vitro transcription system was developed using linear DNA templates that carry the attenuator. The ability of known termination and antitermination proteins to modulate termination at the attenuator was tested. Both NusA and NusG increase the frequency of transcriptional readthrough at the attenuator whereas NusB, S10, and Rho had no significant effect in this system.
Highlights
The NusA and NusGProteins of Escherichia coli Increase the in Vitro Readthrough Frequencyof a Transcriptional AttenuatorPreceding the Gene forthe,6 Subunit of RNA Polymerase*
A series of ancillary factors has been identified in E. coli which are involved in termination and antiterminationreactions in the host itself and during X infection
The concentration of RNA polymerase is closely regulated in Escherichia coli
Summary
From the $Departmentof Microbiology and Immunology, Faculty of Medicine, University of Western Ontario, London, Ontario N6A 5C1, Canada andthe llBanting and Best Departmentof Medical Research, University of Toronto, Toronto, Ontario M5G 1L6, Canuda. The ability of known termination and antitermination proteins to modulate termination at the attenuator was tested Both NusA and NusG increase the frequency of transcriptional readthroughat the attenuator whereas NusB, S10, and Rho had no significant effect in this system. The nusB andnusEmutations did not significantly alter the transcript ratio, implying that they do not function in the transcription of this region From these resultswe tentatively concluded that eitherrpoBa itself was responsive to Rho and NusA even though it had the structuorfea simple terminator or therewas an additional factor-dependent terminator(s) in the intercistronic region downstream of rpoBa. be hereby marked “aduertisement” in accordance with 18 U.S.C. Section 1734 solelyto indicate this fact. MM Tris acetate (pH 7.9), 100 mM KC1, 4 mM magnesium acetate, 0.1 mM EDTA, 0.1 mM dithiothreitol, 500 pM CpC, 2 p~ ATP, 2 p~ CTP, 0.1 pmol of DNA template, 0.5 pmol of RNA polymerase, and additional purified proteinsasindicated at 37 "C for min.This
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