Base Pairing Interaction between 5′- and 3′-UTRs Controls icaR mRNA Translation in Staphylococcus aureus

The presence of regulatory sequences in the 3′ untranslated region (3′-utr) of eukaryotic mrnas controlling rna stability and translation efficiency is widely recognized. in contrast,the relevance of 3′-utrs in bacterial mrna functionality has been disregarded. here,we report evidences showing that around one-third of the mapped mrnas of the major human pathogen staphylococcus aureus carry 3′-utrs longer than 100-nt and thus,potential regulatory functions. we selected the long 3′-utr of icar,which codes for the repressor of the main exopolysaccharidic compound of the s. aureus biofilm matrix,to evaluate the role that 3′-utrs may play in controlling mrna expression. we showed that base pairing between the 3′-utr and the shine-dalgarno (sd) region of icar mrna interferes with the translation initiation complex and generates a double-stranded substrate for rnase iii. deletion or substitution of the motif (uccccug) within icar 3′-utr was sufficient to abolish this interaction and resulted in the accumulation of icar repressor and inhibition of biofilm development. our findings provide a singular example of a new potential post-transcriptional regulatory mechanism to modulate bacterial gene expression through the interaction of a 3′-utr with the 5′-utr of the same mrna. © 2013 ruiz de los mozos et al.