Some small, non-coding RNAs regulate gene expression by binding to messenger RNA and preventing it from being translated into protein. The regulation of one bacterial gene, however, depends not just on one but on two non-coding RNAs, one of which inhibits the other.
Lionello Bossi and his colleagues at the Centre for Molecular Genetics in Gif-sur-Yvette, France, studied the production of a bacterial protein called ChiP, which is involved in sugar uptake. In the absence of sugar, a small RNA called ChiX attaches to ChiP's messenger RNA and prevents protein synthesis. Add sugar, however, and another RNA is produced that binds ChiX and targets it for destruction, allowing production of the ChiP protein.
The discovery of this new feature of small RNAs in living cells could mean that regulatory RNAs identified computationally by sequence may in fact be targets of regulation.