Negative control of protein synthesis after infection with bacteriophage T7.

T7 phage induces two negative control mechanisms of protein synthesis: (a) Host-gene expression is repressed by a "T7 repressor," and (b) early T7 protein synthesis is inhibited by a late phage protein.(a) The repressor for host enzyme synthesis is an early T7 protein. Its gene is none of the known early genes; it is located promotor-proximal to gene 1. The repressor function of this protein can be demonstrated by DNA-dependent enzyme synthesis in vitro.(b) Expression of early phage gene is depressed by a late phage protein or by T7 RNA polymerase. Control takes place on the level of transcription.