Adaptation to carbon starvation: RNase III ensures normal expression levels of bolA1p mRNA and sigma(S).

bolA is a sigma(S)-dependent Escherichia coli morphogene involved in the general cellular adaptation to stress and cell division. In this report it is shown that endoribonuclease RNase III acts as a post-transcriptional modulator of bolA expression under carbon starvation conditions. Unexpectedly RNase III positively regulates bolA1p mRNA levels and stabilities. This effect is also observed when sulA, bfr, uspA and uspB transcripts were analyzed. RNase III is furthermore shown to be necessary for the normal expression of sigma(S), ensuring normal levels of rpoS mRNA and sigma(S) protein under glucose starvation. Since sigma(S) controls a complex regulon of stress-response genes, RNase III is proposed as possible modulator of bacterial cell response to stress.