Control of late messenger RNA synthesis during λ phage development

Abstract

In order to study the role of protein and DNA synthesis in the late gene expression of phage λ, the effects of chloramphenicol and thymidine deprivation on λ mRNA synthesis were investigated. After λ phage infection, normal transcription of late genes, as RNA hybridizable with imm 80 h λ DNA, started 8–10 min after infection, and the rate of synthesis continued to increase almost linearly until lysis. Chloramphenicol, added at or before phage infection, virtually inhibited late transcription. When chloramphenicol was added at various stages of the late phase (after onset of late transcription), the increase of late transcription normally observed was slowed down, and afterwards the rate of late transcription decreased gradually. Similar inhibition of late transcription was also observed when DNA synthesis was inhibited by thymidine deprivation. Under the conditions of the present experiments, chloramphenicol permitted considerable synthesis of λ DNA, whereas thymidine deprivation inhibited DNA synthesis to below 5 % of the control. These results seem to suggest that normal continuation of late transcription requires both replication of phage DNA and protein synthesis continuously throughout λ phage development. Such processes relating to the regulatory mechanism of late transcription are discussed.