Regulation of early gene expression of bacteriophage phi 80: transcriptional regulation by phi 80 gene 30.

The gene30sus620 mutation of bacteriophage phi 80 was mapped close to the left of the cI gene on the standard genetic map. The distance between the mutation (gene30sus620) and the cI gene was about 0.01%, as judged by recombination frequencies. The transcriptional pattern of the mutant showed two distinct differences from that of the wild type; late mRNAs were not synthesized, and early genes were preferentially transcribed rightward in contrast with the predominantly leftward transcription in the wild type. The synthesis of early proteins was also affected. Wild-type phi 80 permits synthesis of five major proteins (pE, pB, pA, pC, and pD) and two minor proteins (pU and pV) upon infection of ultraviolet-irradiated cells. Synthesis of the major proteins was significantly reduced in the mutant, while synthesis of the two minor proteins was enhanced several-fold in this mutant. These results indicate that the gene 30 product regulates the transcription of the two operons in the early region of phi 80, i.e., operon 1, which is transcribed to the left and codes for the five major proteins, and operon 2, which seems to be transcribed to the right and codes for the two minor proteins.