EFFECTS OF AMINO ACID STARVATION UPON CONSTITUTIVE TRYPTOPHAN MESSENGER RNA SYNTHESIS

The effect of amino acid starvation upon the level and rate of synthesis of tryptophan messenger RNA has been studied in RCstr and RCrel Escherichia coli strains. Tryptophan mRNA was assayed by hybridization with DNA from a non-defective tryptophan transducing phage (φ80pt190). In both stringent and relaxed strains, starvation for arginine decreases the level of tryptophan mRNA appreciably (fivefold and sevenfold). Tryptophan mRNA synthesis, as reflected in the rate of labeling by [3H]uridine, is also greatly decreased by arginine starvation in both strains. Apparently tryptophan mRNA is subject to a type of amino acid control which is distinct from the RCstr system described by Stent & Brenner (1961). Hybridization experiments with E. coli DNA show that other species of mRNA do not respond to amino acid starvation in the same way as tryptophan messenger. These experiments, carried out with the same RNA preparations used to measure tryptophan mRNA synthesis, gave results much like those obtained by Friesen (1966). Arginine starvation reduced total mRNA labeling 1.6-fold in the RCrel strains and 4.3-fold in the RCstr strain. © 1968.