ESCHERICHIA-COLI CELL-DIVISION INHIBITOR DICF-RNA OF THE DICB OPERON - EVIDENCE FOR ITS GENERATION INVIVO BY TRANSCRIPTION TERMINATION AND BY RNASE-III AND RNASE E-DEPENDENT PROCESSING

We have established that the long non-coding intercistronic region of the dicB operon of Escherichia coli expresses a trans-acting division inhibitor specified by a region dicF, at most 65 nucleotides-long. The present study deals with the processing of dicBF operon mRNA in vivo, and identifies the dicF gene product as a 53 nucleotide RNA species. A sequence at the end of DicF resembles, and behaves as, a Rho-independent terminator, but further processing of readthrough transcripts, presumably by RNase III, followed by a limited 3′ to 5′ degradation, appears to generate additional DicF-RNA 3′ ends. For the 5′ end of DicF-RNA, our results show that a 190 nucleotide precursor DicF-RNA species is formed by cleavage at an RNase III site, while the 53 nucleotide minimal DicF-RNA is generated by further processing requiring the presence of an active form of RNase E in vivo. These data indicate that an untranslated product derived from an operon RNA can have a regulatory activity by affecting cell division. © 1990.