Identification and characterization of the alc gene product of bacteriophage T4

Bacteriophage T4 infection rapidly and almost completely inhibits transcription of host and other phage DNAs. Two processes have been implicated to date in this inhibition: (1) ADP ribosylation of the alpha subunits of the RNA polymerase, involving gpalt (which is injected with the phage DNA) and, later, gpmod; and (2) the action of the T4 alc/unf gene product, synthesized immediately after infection. The latter unfolds the host genome and also blocks transcription of cytosine-containing DNA. Here, we describe the identification on two-dimensional polyacrylamide gels of gpalc/unf, the more precise mapping of the gene and the identification and analysis of the appropriate DNA sequence from an Unf+ alc mutant.