Bacteriophage 82 gene Q and Q protein. Sequence, overproduction, and activity as a transcription antiterminator in vitro.

Phage 82 gene Q encodes a phage-specific positive regulator of late gene expression, thought, by analogy to the corresponding gene of phage lambda, to be a transcription antiterminator. We have cloned and sequenced the phage 82 gene Q and have overproduced and purified the 82 Q protein. We also have identified and sequenced DNA containing the phage 82 late gene promoter and terminator. We show that purified 82 Q protein is active and specific for DNA containing the 82 late gene promoter in a well defined in vitro transcription reaction: RNA polymerase initiating at the phage 82 late gene promoter and modified by 82 Q protein reads through a downstream transcriptional terminator. We used T1 RNase mapping to confirm that the putative readthrough RNA made in the presence of 82 Q protein is in fact an elongation product of the shorter RNA.