Amino Acid Regulation of the Rates of Synthesis and Chain Elongation of Ribonucleic Acid in Escherichia coli

Abstract

Abstract The rates of synthesis and chain elongation of RNA in stringent (CP 78) and relaxed (CP 79) strains of Escherichia coli have been measured at 27° in the presence and in the absence of a required amino acid. The following observations have been made. 1. Although the rate of uptake of uracil by CP 78 is reduced 200-fold by amino acid starvation, the rate of synthesis of RNA obtained from the specific activity of the intracellular UTP pool is reduced only 9-fold. The rate of synthesis of RNA in CP 79 is unaffected by amino acid deprivation. 2. The number of nascent RNA chains is approximately the same for CP 78 and CP 79, and is unchanged by amino acid starvation. 3. The rates of RNA chain elongation are 23 and 3 nucleotides per sec for unstarved and starved cultures of CP 78, respectively. The rate for CP 79 is virtually unchanged by starvation: 24 and 21 nucleotides per sec for unstarved and starved cultures, respectively. 4. The results are inconsistent with a purely noncoordinate mode of RNA regulation, and suggest that the synthesis of both stable RNA and messenger RNA is restricted, although the relative degree of restriction on the synthetic rates of the two classes cannot be evaluated from these data.