PMID:16631197
| Citation |
Kim, HC, Washburn, RS and Gottesman, ME (2006) Role of E.coli NusA in phage HK022 Nun-mediated transcription termination. J. Mol. Biol. 359:10-21 |
|---|---|
| Abstract |
The 109 amino acid residue Nun protein expressed from prophage HK022 excludes superinfecting phage lambda by arresting transcription on the lambda chromosome near the lambdanut sites. In vitro, the Nun N terminus binds to nascent lambdanutRNA, whereas the C terminus interacts with RNA polymerase and DNA template. Escherichia coli host factors, NusA, NusB, NusE (S10), and NusG, stimulate Nun-arrest. NusA binds the Nun C terminus and enhances formation of the Nun-nutRNA complex. Because of these in vitro activities of NusA, and since a nusA mutation (nusAE136K) blocked Nun in vivo, we assumed that NusA was required for Nun activity. However, using a nusAts strain, we find that NusA is required for termination at nutR but not at nutL. Furthermore, nusAE136K is dominant to nusA(+) for Nun-arrest, both in vitro and in vivo. NusAE136K shows increased affinity for Nun and, unlike NusA(+), can readily be recovered in a ternary complex with Nun and nutRNA. We propose NusAE136K suppresses Nun-arrest when it is a component of the transcription elongation complex, perhaps, in part, by blocking interactions between the Nun C terminus and RNA polymerase and DNA. We also find that in contrast to Nun-arrest, antitermination by lambda N requires NusA. |
| Links |
PubMed Online version:10.1016/j.jmb.2006.02.081 |
| Keywords |
Bacteriophage HK022/genetics; Bacteriophage HK022/metabolism; Bacteriophage lambda/genetics; Bacteriophage lambda/metabolism; DNA-Directed RNA Polymerases/metabolism; Escherichia coli Proteins/genetics; Escherichia coli Proteins/metabolism; Macromolecular Substances; Models, Genetic; Mutation; Peptide Elongation Factors/genetics; Peptide Elongation Factors/metabolism; Terminator Regions, Genetic; Transcription Factors/genetics; Transcription Factors/metabolism; Transcription, Genetic; Viral Proteins/genetics; Viral Proteins/metabolism |
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