3'-Terminal polyadenylation of mRNA in procaryotes

Abstract

Studies in our laboratory have shown that polyadenylation of bacterial mRNA is a common phenomenon, in contrast to general belief. Poly(A)RNA constitutes a surprisingly large fraction of mRNA in Escherichia coli, Bacillus subtilis, and Bacillus brevis. eDNA can be synthesized from bactenal poly(A)RNA using reverse transcriptase only in the presence of oligo(dT) primer, thus providing independent evidence that bacterial rnRNA is poiyadenylated. This facilitated the construction of a cDNA library from poly(A)RNA of B. subtilis. The 3'-terminal sequences adjacent to the poty(A) moiety has been detennined in some clones. We have also examined the polyadenylation of specific E. coli mRNAs. They include the relatively stable mRNA for the outer membrane lipoprotein (lpp) as well as the mRNA for tryptophan synthase (trpA), which serves as paradigm for relatively unstable mRNAs encoding intracellular proteins. So far, all the specific gene transcripts we have probed in B. suhtilis and in E. coli were found to be polyadenylated.