Article: article from journal or magazin.
The RNA recognition motif of yeast translation initiation factor Tif3/eIF4B is required but not sufficient for RNA strand-exchange and translational activity.
Publication types: Journal Article ; Research Support, Non-U.S. Gov'tPublication Status: ppublish
The Saccharomyces cerevisiae TIF3 gene encodes a 436-amino acid (aa) protein that is the yeast homologue of mammalian translation Initiation factor eIF4B. Tif3p can be divided into three parts, the N-terminal region with an RNA recognition motif (RRM) (aa 1-182), followed in the middle part by a sevenfold repeat of 26 amino acids rich in basic and acidic residues (as 183-350), and a C-terminal region without homology to any known sequence (aa 351-436). We have analyzed several Tif3 proteins with deletions at their N and C termini for their ability (1) to complement a tif3delta strain in vivo, (2) to stimulate Tif3-dependent translation extracts, (3) to bind to single-stranded RNA, and (4) to catalyze RNA strand-exchange in vitro. Here we report that yeast Tif3/eIF4B contains at least two RNA binding domains able to bind to single-stranded RNA. One is located in the N-terminal region of the protein carrying the RRM, the other in the C-terminal two-thirds region of Tif3p. The RRM-containing domain and three of the seven repeat motifs are essential for RNA strand-exchange activity of Tif3p and translation in vitro and for complementation of a tif3delta strain, suggesting an important role for RNA strand-exchange activity in translation.
Cell-Free System, Eukaryotic Initiation Factors, Fungal Proteins/chemistry, Fungal Proteins/genetics, Genetic Complementation Test, Peptide Chain Initiation, Translational/genetics, Peptide Initiation Factors, Protein Binding, RNA Nucleotidyltransferases/chemistry, RNA Nucleotidyltransferases/genetics, RNA, Messenger/chemistry, RNA, Messenger/metabolism, Recombinant Fusion Proteins, Saccharomyces cerevisiae/genetics, Saccharomyces cerevisiae Proteins, Sequence Deletion
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