DEAD-box and the related DEAH, DExH and DExD (3) helicases are the most numerous members of SF2 and are ubiquitously present in eukaryotic genomes. These helicases share eight conserved motifs and are commonly refered to as the DExH/D family of helicases. Humans, Arabidopsis and Saccharomyces have 38, 55 and 25 such entities, respectively (4) . Differing from DNA helicases and DExH proteins, DEAD helicases are poor in unwinding long nucleic acid duplexes and are best suited for separating short RNA hybrids. DEAD-box proteins bind with high-affinity RNAprotein complexes while exhibiting little RNA sequence preference. This suggests that the specificity determinants for DEAD helicases may be through the recognition of protein factors. In this regard, a better understanding of the roles for DEAD proteins depends on the clear characterization of their respective interacting proteins.