Transcriptional organization of the S10, spc and alpha operons of Escherichia coli.

We have investigated the transcription patterns at the inter-operon regions between the S10 and spc, and spc and alpha ribosomal protein operons of Escherichia coli. Newly synthesized transcripts were characterized by RNase T1 protection experiments, and accumulated transcripts were mapped with S1 nuclease. With both techniques we found that about 75% of the RNA polymerases transcribing the S10 operon terminated at the position of a typical rho-independent terminator. In contrast, most or all RNA polymerases transcribing the spc operon continued into the alpha operon. Nevertheless, we observed that about 30% of the transcripts of the alpha operon were initiated at the alpha operon promoter.