Hfq affects the length and the frequency of short oligo(A) tails at the 3' end of Escherichia coli rpsO mRNAs.

Polyadenylation plays an important role in RNA degradation in bacterial cells. In Escherichia coli, exoribonucleases, mostly RNase II and polynucleotide phosphorylase, antagonize the synthesis of poly(A) tails by poly(A) polymerase I (PAP I). In accordance with earlier observations showing that only a small fraction of bacterial RNA is polyadenylated, we demonstrate here that approximately 10% of rpsO mRNA harbors short oligo(A) tails ranging from one to five A residues in wild-type cells. We also compared the length, frequency and distribution of poly(A) tails at the 3'-end of rpsO transcripts in vivo in the presence and absence of Hfq, a host factor that in vitro stimulates the activity of PAP I, and found that Hfq affects all three parameters. In the hfq(+) strain the average length of oligo(A) tails and frequency of polyadenylated transcripts was higher than in the hfq(-) strain and a smaller proportion of tails was found at the 3' end of transcripts terminated at the Rho- independent terminator. Our data led us to the conclusion that Hfq is involved in the recognition of 3' RNA extremities by PAP I.