RNA helicases of the DEAD-box and related families have been found to be 
required for all processes involving RNA molecules. Biochemical and genetic 
analyses have shown that at least two RNA helicases are required for translation 
initiation in yeast. Although it is generally believed that these enzymes are 
necessary to unwind secondary structures in the 5' untranslated region of mRNAs, 
their exact role has not been convincingly shown. We discuss here our present 
knowledge of the function of eIF4A and Ded1p, two DEAD-box proteins required for 
translation in eukaryotic cells.