Attenuation and processing of RNA from the rplJL--rpoBC transcription unit of Escherichia coli.

Abstract

Attenuation and processing of the mRNA from the ribosomal protein-RNA polymerase operon rplJL-rpoBC were demonstrated by the analysis of nuclease Sl-resistant RNA.cntdot.DNA hybrids. These hybrids were formed between RNA produced in vivo and specific DNA restriction fragments which span the rplL-rpoB intercistronic region. The 3'' end of the predominant attenuated RNA lies 69 nucleotides beyond the end of the rplL gene following sequence features that are similar to those of other known attenuators. The nonattenuated transcript is normally cleaved in the intercistronic region. In an RNase III mutant strain, the hybrids corresponding to the cleaved nonattenuated mRNA disappear and the expected full-sized hydrid is seen. The cleavage was localized to an area of possible secondary structure in the transcript approximately 200 nucleotides beyond the end of the rplL gene. This demonstrates RNase III processing of E. coli mRNA. The methods used in this study permit the examination of specific ends of large and complex polycistronic mRNA. Such experiments should help in understanding how posttranscriptional events influence gene expression.