From unwinding to clamping — the DEAD box RNA helicase family

RNA helicases of the DEAD box family are highly conserved enzymes with many roles in gene expression. Structural and mechanistic studies are uncovering the basis of their actions and have revealed roles not only in RNA unwinding but also in the remodelling of RNA–protein complexes and in the clamping of RNA to allow nucleation of larger complexes. RNA helicases of the DEAD box family are present in all eukaryotic cells and in many bacteria and Archaea. These highly conserved enzymes are required for RNA metabolism from transcription to degradation and are therefore important players in gene expression. DEAD box proteins use ATP to unwind short duplex RNA in an unusual fashion and remodel RNA–protein complexes, but they can also function as ATP-dependent RNA clamps to provide nucleation centres that establish larger RNA–protein complexes. Structural, mechanistic and molecular biological studies have started to reveal how these conserved proteins can perform such diverse functions and how accessory proteins have a central role in their regulation.