A cII-dependent promoter is located within the Q gene of bacteriophage lambda.
We have found a cII-dependent promoter, PaQ, within the Q gene of bacteriophage lambda. Transcription experiments and abortive initiation assays performed in vitro showed that the promoter strength and the cII affinity of PaQ were comparable to the other cII-dependent lambda promoters, PE and PI. The location and leftward direction of PaQ suggests a possible role in the delay of lambda late-gene expression by cII protein, a phenomenon that has been called cII-dependent inhibition. We have constructed a promoter down mutation, paq-1, by changing a single base pair in the putative cII binding site of the promoter by oligonucleotide site-directed mutagenesis. The paq-1 mutant promoter required about 4-fold higher cII concentrations for maximal activation compared to the wild-type PaQ. We tested the hypothesis that PaQ is responsible in part for the delay of lambda late-gene expression by recombining the paq-1 mutation into a phage showing severe cII-dependent inhibition. We found that the paq-1 mutation relieved the cII-dependent growth defect of this phage. The paq-1 mutation (in combination with lambda cI857) resulted in a clear-plaque phenotype at the permissive temperature of 32 degrees C. The role of the PaQ-initiated antisense transcript in the control of lambda development is discussed.
Hoopes
B C
BC
McClure
W R
WR
D010582:Bacteriophage lambda / Q000235:genetics*; D005786:Gene Expression Regulation; D005814:Genes, Viral; D008242:Lysogeny; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000235:genetics
D014157:Transcription Factors; D014764:Viral Proteins; C039000:cII protein, bacteriophage lambda