TRANSCRIPTION ANALYSIS OF THE STREPTOMYCES-COELICOLOR A3(2) RIBOSOMAL-RNA OPERON

Transcription start sites and processing sites of the Streptomyces coe licolor A3(2) rrnA operon have been investigated by a combination of i n vivo and in vitro transcription analyses. The data from these approa ches are consistent with the existence of four in vivo transcription s ites, corresponding to the promoters P1-P4. The transcription start si tes are located at -597, -416, -334 and -254 relative to the start of the 165 rRNA gene, Two putative processing sites were identified, one of which is similar to a sequence reported earlier in S. coelicolor an d other eubacteria. The pi promoter is likely to be recognized by the RNA polymerase holoenzyme containing sigma(hrdB), the principal sigma factor in S. coelicolor. P2 also shares homology with the consensus fo r vegetative promoters, but has a sequence overlapping the consensus - 35 region that is also present in the -35 regions of P3 and P4. The -3 5 sequence common to P2, P3 and P4 is not similar to any other known c onsensus promoter sequence. In fast-growing mycelium, P2 appears to be the most frequently used promoter. Transcription from all of the rrnA promoters decreased during the transition from exponential to station ary phase, although transcription from pi and P2 ceased several hours before that from P3 and P4.