Poster abstracts
Poster number 49 submitted by Zhaofeng Gao
The DEAD-box RNA helicases Ded1p and eIF4A function simultaneously on the eukaryotic initiation factor 4F
Zhaofeng Gao (Center for RNA Molecular Biology and Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106), Heath Bowers (Center for RNA Molecular Biology and Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106), Andrea Putnam (Center for RNA Molecular Biology and Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106), Ulfpeter Gunther (Center for RNA Molecular Biology and Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106), Eckhard Jankowsky (Center for RNA Molecular Biology and Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106)
Abstract:
The eukaryotic translation initiation factor 4F (eIF4F) consists of the large scaffolding and RNA binding protein eIF4G, the cap-binding protein eIF4E, and the loosely associated DEAD-box RNA helicase eIF4A. In Saccharomyces cerevisiae, another DEAD-box RNA helicase, Ded1p also interacts with eIF4G. Here, we show that the two DEAD-box helicases are functionally coupled to stimulate remodeling of structured RNA.
Using recombinant purified proteins, we show that Ded1p directly interacts with eIF4A, and that eIF4A stimulates RNA unwinding by Ded1p. Ded1p also directly interacts with eIF4G/E, and eIF4G/E promotes RNA binding by Ded1p, but inhibits RNA unwinding by Ded1p by interfering with oligomerization of the helicase. Addition of eIF4A to the eIF4G/4E-Ded1p complex stimulates the RNA unwinding well above the level of stimulation seen for Ded1p with eIF4A alone. The eIF4G/E/A-Ded1p complex shows a strong preference for remodeling of substrates with 3' unpaired tails, over those with 5' tails, a feature not seen with both helicases alone. Moreover, Ded1p significantly enhances the affinity of eIF4F for RNA with a 5' cap.
Collectively, our results reveal intricate functional coupling between Ded1p and the eIF4F components. The interactions rationalize previously observed genetic interactions between the eIF4F components and Ded1p, and indicate that both DEAD-box helicases, eIF4A and Ded1p function simultaneously in the eIF4F complex.
Keywords: DEAD-box RNA helicase, translation initiation, eIF4F