U-turns and regulatory RNAs

Conventional antisense RNAs, such as those controlling plasmid replication and maintenance, inhibit the function of their target RNAs rapidly and effi ciently Novel findings show that a common Ii-turn loop structure mediates f ast RNA pairing in the majority of these RNA controlled systems. Usually, a n antisense RNA regulates a single, cognate target RNA only. Recent reports , however, show that antisense RNAs can act as promiscuous regulators that control multiple genes in concert to integrate complex physiological respon ses in Escherichia coli.