Abstract
The relationship of early transcriptive events to protein synthesis has been studied in protoplasts of bacteriophage T4-infected Escherichia coli by division of the infection cycle into a period of transcription and one of translation with inhibitors of RNA and protein synthesis. The accumulation of specific messengers during an initial incubation in the presence of 5-methyltryptophan or chloramphenicol was determined by the inhibition of further RNA synthesis with rifamycin and the measurement of the increase in the activity of various early enzymes after the restoration of protein synthesis. Three groups of early enzymes could be distinguished operationally according to the manner in which the respective messenger RNA accumulated during incubation with 5-methyltryptophan. In the case of one early enzyme, deoxynucleotide kinase, the messenger RNA did not accumulate in the presence of 5-methyltryptophan, a suggestion that the transcription of this region of the phage DNA requires the prior synthesis of a specific phage-induced protein. It was also shown that early viral transcription is severely limited when the synthesis of phage-induced proteins is inhibited with chloramphenicol. These studies suggest that early transcriptive events in viral development may be regulated by the synthesis of specific proteins.
Highlights
Three groups of early enzymes could be distinguished operationally according to the manner in which the respective messenger RNA accumulated during incubation with 5methyltryptophan
As an initial approach to the understanding of the mechanisms regulating the synthesis of the early enzymes in phage-infected cells, we have attempted to define the level of protein synthesis, either transcription or translation, at which these mechanisms are operative
We have utilized an experimental approach previously described by Guthrie and Buchanan, in which the processes of transcription and translation for the synthesis of early enzymes were separated by the use of inhibitors of RNA and protein synthesis [5]
Summary
Three groups of early enzymes could be distinguished operationally according to the manner in which the respective messenger RNA accumulated during incubation with 5methyltryptophan. In the case of one early enzyme, deoxynucleotide kinase, the messenger RNA did not accumulate in the presence of 5-methyltryptophan, a suggestion that the transcription of this region of the phage DNA requires the prior synthesis of a specific phage-induced protein. It was shown that early viral transcription is severely limited when the synthesis of phage-induced proteins is inhibited with chloramphenicol
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