Identification of the functional binding domains of eukaryotic initiation factor eIF4G with 3’ Cap‐independent translation element of Barley Yellow Dwarf Virus (LB203)

Different from canonical translation initiation, some plant viral RNAs lack a 5’cap (an unusual 7‐methyl guanosine linked by a 5’to 5’ triphosphate). They utilize a cap independent translation element (CITE) to efficiently start translation. Barley yellow dwarf virus (BYDV) has a translation element (BTE) located in its 3’UTR mRNA. BTE binds with eukaryotic initiation factor eIF4G (one subunit of heterodimer of eIF4F) and recruits other initiation factors to assemble the ribosome preinitiation complex for synthesis of viral proteins. BYDV is one of the world‐wide economically most important viruses causing severe crop loss. How BTE mediate BYDV translation is still unclear. By measuring fluorescence anisotropy of labeled RNA, here we report 3’BTE binds with a truncated fragment of eIF4G, eIF4G601‐1196 (contained amino acid residue from 601 to 1196). The equilibrium dissociation constants (Kd) of this binding is 39.5±3.5 nM. Adding eIF4E, the cap binding protein, can increase the binding ability of eIF4G601‐1196 with 3’BTE. eIF4G601‐1196•4E complex binds with 3’BTE 5.8 folds tighter than eIF4G601‐1196 alone, with the equilibrium dissociation constant 6.78±1.49nM. Further circular dichroism spectra (CD) and thermodynamic studies will characterize the binding of the eIF4G with 3’ BTE. These results suggest eIF4E plays an indirect role in translation initiation, even for an uncapped virus. Grant Funding Source : NSF MCB 1157632