The use of RNAs complementary to specific mRNAs to regulate the expression of individual bacterial genes.

A naturally occurring small RNA molecule ( micF RNA), complementary to the region encompassing the Shine-Dalgarno sequence and initiation codon of the ompF mRNA, is known to block the expression of that mRNA in E. coli. We have constructed a plasmid that produces a complementary RNA to the E. coli lpp mRNA (mic[Ipp] RNA). Induction of the mic(Ipp) gene efficiently blocked lipoprotein production and reduced the amount of lpp mRNA. Two mic(ompC) genes were similarly engineered and their expression was found to inhibit drastically production of OmpC. Analysis of several types of mic(ompA) genes suggests that micRNAs complementary to regions of the mRNA likely to come in contact with ribosomes were most effective. The novel capabilities of this artificial mic system provide great potential for application in both procaryotic and eucaryotic cells.