The bacteriophage lambdaQ anti-terminator protein regulates late gene expression as a stable component of the transcription elongation complex.
The Q protein of bacteriophage lambda (lambdaQ) is a transcription anti-terminator required for the expression of the phage's late genes under the control of promoter P(R'). To effect terminator read-through, lambdaQ must gain access to RNA polymerase (RNAP) via a promoter-restricted pathway. In particular, lambdaQ modifies RNAP by binding a specific DNA site embedded in P(R') and interacting with RNAP in the context of a specific paused early elongation complex. The resultant lambdaQ-modified transcription elongation complex is competent to read through downstream termination signals. Here we use a chromatin-immunoprecipitation assay to test the hypothesis that lambdaQ functions as a stable component of the transcription elongation complex. Our results indicate that, in vivo, the lambdaQ-modified transcription elongation complex contains Q as a stably associated subunit. Furthermore, we find that in the physiologically relevant context of an induced lambda lysogen, Q remains stably associated with RNAP as it transcribes at least 22 kb of the phage late operon. Thus, our findings suggest that the promoter-specific pathway leading to lambdaQ-mediated terminator read-through results in the formation of a highly stable lambdaQ-containing transcription elongation complex capable of traversing the entire late operon.
Deighan
Padraig
P
Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Ave., Boston, MA 02115, USA.
Hochschild
Ann
A
D010582:Bacteriophage lambda / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins; D015967:Gene Expression Regulation, Viral; D008242:Lysogeny / Q000235:genetics; D046912:Multiprotein Complexes / Q000378:metabolism; D011401:Promoter Regions, Genetic; D050436:Regulatory Elements, Transcriptional; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000378:metabolism*
D004268:DNA-Binding Proteins; D046912:Multiprotein Complexes; C066119:Q protein, Bacteriophage lambda; D014764:Viral Proteins