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J. Biol. Chem., Vol. 281, Issue 34, 24351-24364, August 25, 2006

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Wheat Eukaryotic Initiation Factor 4B Organizes Assembly of RNA and eIFiso4G, eIF4A, and Poly(A)-binding Protein^*

From the Department of Biochemistry, University of California, Riverside, California 92521-0129

The eukaryotic translation initiation factor (eIF) 4B promotes the RNA-dependent ATP hydrolysis activity and ATP-dependent RNA helicase activity of eIF4A and eIF4F during translation initiation. Although this function is conserved among plants, animals, and yeast, eIF4B is one of the least conserved of initiation factors at the sequence level. To gain insight into its functional conservation, the organization of the functional domains of eIF4B from wheat has been investigated. Plant eIF4B contains three RNA binding domains, one more than reported for mammalian or yeast eIF4B, and each domain exhibits a preference for purine-rich RNA. In addition to a conserved RNA recognition motif and a C-terminal RNA binding domain, wheat eIF4B contains a novel N-terminal RNA binding domain that requires a short, lysine-rich containing sequence. Both the lysine-rich motif and an adjacent, C-proximal motif are conserved with an N-proximal sequence in human and yeast eIF4B. The C-proximal motif within the N-terminal RNA binding domain in wheat eIF4B is required for interaction with eIFiso4G, an interaction not reported for other eIF4B proteins. Moreover, each RNA binding domain requires dimerization for binding activity. Two binding sites for the poly(A)-binding protein were mapped to a region within each of two conserved 41-amino acid repeat domains on either side of the C-terminal RNA binding domain. eIF4A bound to an adjacent region within each repeat, supporting a central role for these conserved eIF4B domains in facilitating interaction with other components of the translational machinery. These results support the notion that eIF4B functions by organizing multiple components of the translation initiation machinery and RNA.

Received for publication, June 6, 2006 , and in revised form, June 21, 2006.

^* This work was supported by United States Department of Agriculture Grant 2003-35100-13375. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The on-line version of this article (available at http://www.jbc.org) contains supplemental Fig. 1.

¹ To whom correspondence should be addressed. Tel.: 951-827-7298; Fax: 951-827-4434; E-mail: drgallie{at}citrus.ucr.edu.

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				S. Cheng and D. R. Gallie eIF4G, eIFiso4G, and eIF4B Bind the Poly(A)-binding Protein through Overlapping Sites within the RNA Recognition Motif Domains J. Biol. Chem., August 31, 2007; 282(35): 25247 - 25258. [Abstract] [Full Text] [PDF]