RIBOSOMAL-RNA TRANSCRIPTION AND GROWTH RATE-DEPENDENT REGULATION OF RIBOSOME SYNTHESIS IN ESCHERICHIA-COLI

The synthesis of ribosomal RNA is the rate-limiting step in ribosome s ynthesis in bacteria. There are multiple mechanisms that determine the rate of rRNA synthesis, Ribosomal RNA promoter sequences have evolved for exceptional strength and for regulation in response to nutritiona l conditions and amino acid availibility. Strength derives in part fro m an extended RNA polymerase (RNAP) recognition region involving at le ast two RNAP subunits, in part from activation by a transcription fact or and in part from modification of the transcript by a system that pr events premature termination. Regulation derives from at least two mec hanistically distinct systems, growth rate-dependent control and strin gent control. The mechanisms contributing to rRNA transcription work t ogether and compensate for one another when individual systems are ren dered inoperative.