Amino acid regulation of messenger ribonucleic acid synthesis in T4-infected Escherichia coli

Abstract

The effect of amino acid starvation on the synthesis of T4 messenger ribonucleic acid (mRNA) was studied by measuring the uptake of labeled precursors into Escherichia coli cells which were infected prior to amino acid starvation. The results indicated that the rate of uptake of labeled uracil and adenine into T4 mRNA was reduced by approximately 50% when amino acids were withheld from stringent K-12 strains, but not when they were withheld from a stringent strain B or a relaxed strain K-12. Chloramphenicol reversed the inhibition of precursor uptake resulting from amino acid starvation in the RC(str) K-12 strain. Pulse-labeling experiments reinforced these observations. Pulse-decay experiments in conjunction with actinomycin D indicated that the observed pattern of precursor uptake was probably not due to differences in mRNA decay rate. It is concluded that if amino acids exert any direct effect on the synthesis of T4 mRNA such an effect is much smaller than that observed for bulk RNA synthesis in the uninfected cell. These experiments also indicated that actual translation of the genetic message is not necessary for its transcription.