Evidence for a diffusible T4 bacteriophage protein governing the initiation of delayed early RNA synthesis

Two forms of prereplicative phage RNA can be discerned in Escherichia coli early after infection with bacteriophage T4, immediate early and delayed early RNA. The transition from immediate early to delayed early RNA synthesis is inhibited by chloramphenicol. The present work presents evidence for the existence of a phage-specific protein, which effects this transition. Delayed early RNA formation was measured by a cistron-specific enzyme-forming-capacity method, in which RNA synthesized in the presence of chloramphenicol was allowed to express itself into enzyme activity after (i) the addition of rifampin to inhibit further transcription and (ii) subsequent removal of chloramphenicol. As representatives of delayed early transcription, the two phage-specific enzymes dCTPase and deoxynucleotide kinase were chosen. Primary infection with a phage mutant defective in one of these two enzymes was found to induce a diffusible factor, which in the presence of chloramphenicol could effect the formation of delayed early RNA corresponding to the missing enzyme, upon superinfection with wild-type phage. The activity of this factor, acting in trans, was abolished by the amino acid analogue ethionine. Mutation in the suA gene of the host did not relieve phage of the apparent need for protein synthesis in the transition from immediate early to delayed early phage RNA synthesis.