Bacteria are constantly challenged by changing environmental conditions.  They employ a number of post-transcriptional control mechanisms including trans-acting proteins, small regulatory RNAs (sRNAs) as well as features inherent to mRNA structure, which permit a fast adaptation to new environments or to different kinds of stress.

We are focusing on post-transcriptional control mechanisms exerted by the global regulatory protein Hfq in conjunction with sRNAs in Bacteria, with emphasis on the human pathogen Pseudomonas aeruginosa. These studies revealed novel molecular modes of sRNA-mediated regulation as well as Pseudomonas sRNAs contributing to pathogenicity. We have identified the P. aeruginosa regulatory RNA PhrS as an activator of PqsR synthesis, a key quorum sensing regulator involved in the production of the virulence factor pyocyanin. Genetic studies revealed a novel mode of regulation by a sRNA, whereby PhrS uses a base-pairing mechanism to activate a short upstream open reading frame to which the pqsR gene is translationally coupled. Expression of phrS requires the oxygen-responsive regulator ANR. Thus, PhrS is the first bacterial sRNA that provides a regulatory link between oxygen availability and quorum sensing, which may impact on oxygen-limited growth in P. aeruginosa biofilms.  

Other projects are directed towards a better understanding of post-transcriptional regulatory mechanisms in the model crenarchaeon Sulfolobus solfataricus (Sso) . These studies revealed the sequence of events in archaeal translation initiation as well as unprecedented function(s) of archaeal translation initiation factors. We have shown that the ?-subunit of translation initiation factor aIF2 exhibits –besides its requirement for initiator-tRNA binding- an additional function with resemblance to the eukaryotic cap-complex.  It binds to the 5´-triphosphate end of mRNAs and counteracts mRNA decay in Sso by a recently identified Sso RNAse with 5´->3´directionality. In addition, ongoing studies concentrate on the elucidation of the function of archaeal Sm proteins in RNA metabolism and molecular mechanisms underlying non-coding RNA mediated regulation in Sso.