The DEAD-box RNA helicase Ded1 from yeast is associated with the signal recognition particle (SRP), and its enzymatic activity is regulated by SRP21

Abstract

ABSTRACTThe DEAD-box RNA helicase Ded1 is an essential yeast protein involved in translation initiation. It belongs to the DDX3 subfamily of proteins implicated in developmental and cell-cycle regulation.In vitro, the purified Ded1 protein is an ATP-dependent RNA binding protein and an RNA-dependent ATPase, but it lacks RNA substrate specificity and enzymatic regulation. Here we demonstrate by yeast genetics,in situlocalization andin vitrobiochemical approaches that Ded1 is associated with, and regulated by, the signal recognition particle (SRP), which is a universally conserved ribonucleoprotein complex required for the co-translational translocation of polypeptides into the endoplasmic reticulum lumen and membrane. Ded1 is physically associated with SRP componentsin vivoandin vitro. Ded1 is genetically linked with SRP proteins. Finally, the enzymatic activity of Ded1 is inhibited by SRP21 with SCR1 RNA. We propose a model where Ded1 actively participates in the translocation of proteins during translation. Our results open a new comprehension of the cellular role of Ded1 during translation.