Antiterminator-dependent modulation of transcription elongation rates by NusB and NusG.
Ribosomal RNA is transcribed about twice as fast as messenger RNA in vivo, and this increased transcription rate requires the rrn boxA antitermination system. Because several Nus factors have been implicated in rrn antitermination, we have examined the role of NusB, NusE and NusG in controlling the rate of rrn boxA-mediated transcript elongation. In vivo RNA polymerase transcription rates were determined by measuring the rate of appearance of lacZ transcript using a plasmid that contained an inducible T7 promoter fused to the rrn boxA sequence followed by the lacZ gene. This plasmid was introduced into Escherichia coli mutant strains that can be conditionally depleted of NusG, or that carry a deficient nusB gene or a nusE mutation. We found that, in addition to the rrn boxA antiterminator sequence, both NusG and NusB were required to maintain the high transcription rate. The nusE mutation used in this study may be specific for lambda antitermination, as it did not influence the boxA-mediated increase in transcription rate.
Zellars
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Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA.
Squires
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D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D010445:Peptide Elongation Factors / Q000235:genetics / Q000502:physiology*; D012269:Ribosomal Proteins / Q000235:genetics / Q000502:physiology*; D013728:Terminator Regions, Genetic; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic; D019895:Transposases
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C074952:NusB protein, E coli; C070291:NusG protein, E coli; D010445:Peptide Elongation Factors; D012269:Ribosomal Proteins; D014157:Transcription Factors; C029537:ribosomal protein S10; C095509:IS10 transposase; D019895:Transposases