Regulation of the expression of bacterial iron transport genes: possible role of an antisense RNA as a repressor.

Expression of the iron transport gene, fatB and fatA, in the bacterium Vibrio anguillarum 775 is negatively regulated by the iron concentration in the medium. Here, we show that iron represses fatB and fatA mRNA levels and concomitantly induces the synthesis of an antisense RNA (RNA alpha). The presence of RNA alpha correlates with the inhibition of FatA protein synthesis and thus may play a role in the iron repression of fatA expression. Since the 5' end of RNA alpha maps 125 nucleotides upstream from the start codon of fatA and this RNA also extends into the coding region of fatB, it may also be involved in the iron regulation of fatB expression. RNA alpha may thus constitute a novel component of the bacterial iron regulatory circuit.