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.

Carbon Isotopes↗

PubMed1969

Transient activation of RNA polymerase in Escherichia coli B after infection with bacteriophage T4.

Sköld and Buchanan(1) have reported that there is a rapid loss of RNA polymerase activity in Escherichia coli B after infection with T4 bacteriophage. More recent studies on the mechanism of this inactivation have been made in this(2) and other laboratories.(3, 4) In this communication, we report the observation of a transient stimulation of RNA polymerase activity when measurement is made immediately after infection and when cells are ruptured by a gentle lysis procedure. The increase in activity is independent of the synthesis of protein. The activity in the extracts of infected cells is lost by treatment of the extract with antibody to E. coli RNA polymerase and is refractive to the inhibitory action of the antibiotic rifamycin. Hybridization experiments indicate that an RNA transcribed almost exclusively from a T4 DNA template is the product of incubation of extracts of infected cells with a reaction mixture containing an exogenous primer (salmon sperm DNA). These findings are consistent with the hypothesis that one of the first steps in phage infection is the formation of a transcription complex containing T4 DNA and E. coli RNA polymerase.

Animals↗

PubMed1969

Patterns of RNA synthesis in T5-infected cells. I. As studied by the technique of DNA-RNA hybridization-competition.

The RNA-labeling patterns obtained after T5 infection of Escherichia coli F agree with the patterns of protein labeling published by McCorquodale and Buchanan.(1) Three distinct classes of RNA formed sequentially during the period of viral development can be recognized by the DNA-RNA hybridization-competition technique. Class I RNA is formed within 5 minutes after the beginning of viral metabolism and corresponds to the RNA synthesized in response to infection with the 8 per cent segment of T5 DNA. Protein synthesis directed by this 8 per cent segment is required in some capacity for the cessation of class I synthesis and the beginning of the synthesis of class II at 4 to 5 min after infection. Class III RNA synthesis begins between 9 and 12 minutes. Its appearance is prevented when chloramphenicol is added immediately after complete expression of class I functions.

Bacterial Proteins↗

PubMed1968