The alpha subunit of E. coli RNA polymerase activates RNA binding by NusA.
The Escherichia coli NusA protein modulates pausing, termination, and antitermination by associating with the transcribing RNA polymerase core enzyme. NusA can be covalently cross-linked to nascent RNA within a transcription complex, but does not bind RNA on its own. We have found that deletion of the 79 carboxy-terminal amino acids of the 495-amino-acid NusA protein allows NusA to bind RNA in gel mobility shift assays. The carboxy-terminal domain (CTD) of the alpha subunit of RNA polymerase, as well as the bacteriophage lambda N gene antiterminator protein, bind to carboxy-terminal regions of NusA and enable full-length NusA to bind RNA. Binding of NusA to RNA in the presence of alpha or N involves an amino-terminal S1 homology region that is otherwise inactive in full-length NusA. The interaction of the alpha-CTD with full-length NusA stimulates termination. N may prevent termination by inducing NusA to interact with N utilization (nut) site RNA rather than RNA near the 3' end of the nascent transcript. Sequence analysis showed that the alpha-CTD contains a modified helix-hairpin-helix motif (HhH), which is also conserved in the carboxy-terminal regions of some eubacterial NusA proteins. These HhH motifs may mediate protein-protein interactions in NusA and the alpha-CTD.
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Banting and Best Department of Medical Research and Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario M5G 1L6, Canada.
Kuznedelov
K
K
Mushegian
A
A
Severinov
K
K
Greenblatt
J
J
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D010445:Peptide Elongation Factors; D012329:RNA, Bacterial / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D035602:Transcriptional Elongation Factors
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D010445:Peptide Elongation Factors; D012329:RNA, Bacterial; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D035602:Transcriptional Elongation Factors; C064872:antiterminator proteins, Bacteria; C068727:nusA protein, E coli; D012321:DNA-Directed RNA Polymerases; C113275:RNA polymerase alpha subunit