A GENETIC LOCUS FOR THE REGULATION OF RIBONUCLEIC ACID SYNTHESIS

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Abstract
The methionine-requiring strain 58-161 of E. coli K12 continues to synthesize ribosomal RNA during methionine starvation, in contrast to amino acid auxotrophs of other E. coli lines, which stop synthesis when deprived of the required amino acid. Study of mulitple auxotrophic derivatives of strain 58-161 requiring additional amino acids for growth revealed that in this strain the normally stringent control of ribosomal RNA synthesis by amino acids is relaxed. Conjugation experiments in which Hfr variants of strain 58-161 were crossed to F- bacteria subject to normal, stringent amino acid control showed that there exists a locus, RC, on the bacterial chromosome that in its "relaxed" RCrel allelic state of the 58-161 line produces less stringent amino acid control of ribosomal RNA synthesis than its normal "stringent" RCst allele. The RC locus could be either a regulator gene concerning the synthesis of repressors of RNA synthesis or an operator gene governing the function of an operon that serves as the direct chromosomal template of ribosomal RNA or generates an ephemeral cytoplasmic product whose continual replenishment is required for RNA synthesis.