Binding of Eukaryotic Initiation Factor (eIF) 4F to Barley Yellow Dwarf Virus (BYDV) 3′ UTR Correlates Well With Protein Synthesis Efficiency

Abstract

BYDV belonging to the luteoviridae family is an economically important plant virus lacking a 5′ cap and 3′poly (A) tail and is translated by cap‐independent translation (CIT) mechanism. The BYDV 3′ Untranslated Region (UTR) translation enhancer element (BTE) stimulates CIT initiation at the 5′upstream AUG via base‐pairing (kissing stem loop interaction) to a complementary loop, 5′UTR SL‐D. 3′ BTE recruits eIFs and transfers them to the 5′ end of the viral RNA where translation initiates.Wild type BTE and BTE mutants with in‐vitro translation efficiencies from 5–164 % were studied. eIF4F binding is the first committed step in cap‐dependent protein synthesis. The role of eIF4F in viral protein synthesis is not fully understood.eIF4F binding to BTE and BTE mutants gave equilibrium binding constant values (Kds) which are a measure of relative complex stability. We show: 1) translation efficiencies correlated well with eIF4F binding with one exception; 2) Kinetics, higher activation energy and interaction of other eIFs contribute; 3) BTE and BTE mutants‐eIF4F interaction is both enthalpically (52–90%) and entropically favorable with more enthalpic contribution to ΔG° at 25°C. The stability measurements and kinetics determine the nature of interactions and provides unique information on the sequential assembly of the initiation complex and it's binding to viral mRNA.Grant Support: NSF MCB 1157632