Abstract
Cap-binding proteins specifically bind to the 7-methyl guanosine (m7G) functional group at the 5' end of eukaryotic mRNAs. A novel Arabidopsis thaliana protein has been identified that has sequence similarity to cap-binding proteins but is clearly a different form of the protein. The most obvious primary sequence difference is the substitution of two of the eight conserved tryptophan residues with other aromatic amino acids in the novel protein. Analogous forms of this novel protein appear to be present in other higher eukaryotes but not in yeast. Analysis of the native and recombinant forms of the novel protein by retention on m7GTP-Sepharose indicate that it is a functional cap-binding protein. Measurements of the dissociation constant for this protein indicate that it binds m7GTP 5-20-fold tighter than eukaryotic initiation factor (eIF)(iso)4E. The novel protein also supports the initiation of translation of capped mRNA in vitro. Biochemical analysis and yeast two-hybrid data indicate that it interacts with eIF(iso)4G to form a complex. Based on these observations, this protein appears to be able to function as a cap-binding protein and is given the designation of novel cap-binding protein (nCBP).
Highlights
Cap-binding proteins1 recognize and bind the m7G functional group found at the 5Ј end of most eukaryotic cellular mRNAs
The mammalian eIF4E is known to be phosphorylated at Ser-209, and the phosphorylation state appears to correlate with activity of the protein
We have identified a novel cap-binding protein from Arabidopsis thaliana that is distinct in both amino acid sequence and m7GTP binding properties from eIF4E or eukaryotic initiation factor (eIF)(iso)4E and appears to be present only in higher eukaryotes
Summary
Cap-binding proteins (eIF4E)1 recognize and bind the m7G functional group found at the 5Ј end of most eukaryotic cellular mRNAs (for recent reviews, see Refs. 1 and 2). Measurements of the dissociation constant for this protein indicate that it binds m7GTP 5–20-fold tighter than eukaryotic initiation factor (eIF)(iso)4E. We have identified a novel cap-binding protein (nCBP) from Arabidopsis thaliana that is distinct in both amino acid sequence and m7GTP binding properties from eIF4E or eIF(iso)4E and appears to be present only in higher eukaryotes.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have