Kinetics of P22 early gene expression suggests a cro-like regulatory function.

Analysis of phage-specified protein synthesis after phage infection of UV-irradiated cells shows a turn-off of early gene expression, a regulatory event that is independent of the known P22 regulatory functions. This supports the suggestion of a cro lambda-like function in P22. We have identified the products of genes 18 and int as contributing to the complex 40,000 dalton band in our SDS-polyacrylamide gels. Both gene products appear to be subject to regulation by the cro-like function of P22. Proteins of 33,000, 29,000, 27,000, 25,000, and 24,000 MW, specified by as yet unidentified P22 genes of the early leftward operon, are regulated by the same function. Our data suggest that the cro-like function is expressed from the early rightward operon.