Base Pairing Interaction between 5′- and 3′-UTRs Controls icaR mRNA Translation in Staphylococcus aureus
A model of the potential post-transcriptional regulatory mechanism controlling IcaR expression mediated by the 3′-UTR interaction with the Shine-Dalgarno region is shown. Once icaR gene is transcribed, the 3′-UTR interacts either in trans or cis with the 5′-UTR through the anti-SD UCCCCUG motif. This interaction has two main consequences: i) it interferes with ribosome access to the SD region to inhibit the formation of the translational initiation complex and ii) it promotes RNase III-dependent mRNA decay. In consequence, IcaR repressor is less expressed and thus icaADBC transcription occurs, favouring PIA-PNAG biosynthesis and biofilm development. When the interaction between icaR 3′- and 5′-UTR regions does not happen, ribosome binds the SD and proceeds with IcaR protein translation. The resulting IcaR protein binds to icaADBC operon promoter inhibiting its transcription and consequently biofilm formation.