The relationship of DNA replication to the control of protein synthesis in protoplasts of T4-infected Escherichia coli B.

The relationship of DNA replication to the control of early enzyme synthesis and the formation of late proteins was studied in protoplasts of E. coli B cells infected with an amber mutant, T4am130. In this phage-host system the bacterial DNA is not completely degraded, and the onset and the extent of phage DNA synthesis could be regulated by use of 5-fluorodeoxyuridine and thymidine. It was found that DNA replication is necessary for the transcription of "late" regions of the phage genome and, thus, for the synthesis of late proteins. In addition, the sustained synthesis of late RNA and the tail-fiber protein was shown to require the continued replication of DNA. Furthermore, the mechanism regulating the cessation of early enzyme synthesis appeared to become operative shortly after the onset of DNA replication and required a limited amount of DNA synthesis for its full expression.