Antisense RNA regulation of the fatB iron transport protein gene in Vibrio anguillarum.

We have recently identified an antisense RNA (RNA alpha) that regulates the expression of the fatA iron transport gene encoding the outer membrane receptor for the iron-anguibactin complex. In this work, we demonstrate that RNA alpha also inhibits the expression of fatB, which encodes a 35 kDa iron transport protein and has domains homologous to other periplasmic transport proteins. The expression of fatA and fatB is repressed under iron-rich conditions, in which RNA alpha is induced. RNA alpha is homologous to two-thirds of the coding region of fatB. By cloning RNA alpha coding sequences immediately downstream of a tet promoter, we were able to obtain constitutive expression of the antisense RNA. The cloned region contains approximately 83% of the 650 nucleotide RNA alpha and is complementary to only 51% of the fatB mRNA but is still capable of causing a repression of the expression of the fatB gene. Our results in this work demonstrate that RNA alpha probably affects the stability of the fatB-specific mRNA.