Members of the DEAD box family of RNA helicases, which are characterised by the 
presence of twelve conserved motifs (including the signature D-E-A-D motif) 
within a structurally conserved 'helicase' core, are involved in all aspects of 
RNA metabolism. Apart from unwinding RNA duplexes, which established these 
proteins as RNA helicases, DEAD box proteins have been shown to also catalyse 
RNA annealing and to displace proteins from RNA. DEAD box proteins generally act 
as components of large multi-protein complexes and it is thought that 
interactions, via their divergent N- and C-terminal extensions, with other 
factors in the complexes may be responsible for the many different functions 
attributed to these proteins. In addition to their established crucial roles in 
the manipulation of RNA structure, it is becoming increasingly clear that 
several members of the DEAD box family act as regulators of transcription. In 
this review I shall focus on DDX5 (p68) and the highly related DDX17 (p72), two 
proteins for which there is a large body of evidence demonstrating that they 
function in transcriptional regulation. This article is part of a Special Issue 
entitled: The Biology of RNA helicases - Modulation for life.