Eukaryotic Initiation Factor (eIF)4F Binding to Barley Yellow Dwarf Virus (BYDV) 3′ Untranslated Region (3′ UTR) Correlates with Translation Efficiency [Gene Regulation]

December 30th, 2013 by Banerjee, B., Goss, D. J.

Eucaryotic initiation factor (eIF) 4F binding to mRNA is the first committed step in cap-dependent protein synthesis. Barley Yellow Dwarf Virus (BYDV) employs a cap-independent mechanism of translation initiation which is mediated by a structural element BTE (BYDV translation element) located in the 3′ UTR of its mRNA. eIF4F bound the BTE and a translationally inactive mutant with high affinity; thus questioning the role of eIF4F in translation of BYDV. To examine the effects of eIF4F in BYDV translation initiation, BTE mutants with widely different in vitro translation efficiencies ranging from 5-164% compared to WT were studied. Using fluorescence anisotropy to obtain quantitative data, we show 1) the equilibrium binding affinity (complex stability) correlated well with translation efficiency, whereas the on rate of binding did not. 2) Unidentified proteins in wheat germ extract (WGE) prevented eIF4F binding to mutant BTE but not WT BTE. 3) BTE mutants-eIF4F interactions were found to be both enthalpically and entropically favorable with an enthalpic contribution of 52-90% to ∆G° at 25°C suggesting hydrogen bonding contributes to stability and 4) in contrast to cap-dependent and tobacco etch virus (TEV) Internal Ribosome Entry Site (IRES) interaction with eIF4F, PABP did not increase eIF4F binding. Further, the eIF4F bound to the 3′ BTE with higher affinity than for either m7G cap or TEV IRES, suggesting that the 3′ BTE may play a role in sequestering host cell initiation factors and possibly regulating the switch from replication to translation.
  • Posted in Journal of Biological Chemistry, Publications
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