Eukaryotic translation initiation factor eIF4G utilizes different domains to coordinate with eIF4A, eIF4B and eIF4E in binding 3′ Cap‐independent translation element of Barley Yellow Dwarf Virus

Abstract

Barley Yellow Dwarf Virus (BYDV) lacks a 5′ (7‐methyl guanosine) cap as well as a 3′poly A tail. Like many plant viruses, BYDV contains a cap independent translation element (CITE) in the 3′ untranslated region of the viral mRNA. BTE (Barley Yellow Dwarf Virus like cap‐independent element) is one of the well characterized CITEs. BTE mediated translation primarily depends on eukaryotic initiation factor eIF4G. BTE binds to eIF4G; however, the details of BTE initiated translation are still unclear. Three eIF4G deletion mutants with different domain organization were used to investigate BTE interaction with eIF4G: eIF4G601‐1196 is the eIF4G truncated fragment containing amino acids from 601 to 1196, including eIF4E, central eIF4A, eIF4B binding domains and the possible BTE binding region; eIF4G601‐1488 is a longer fragment with one additional C‐terminal eIF4A binding domain; eIF4G742‐1196 is a shorter deletion mutant lacking the eIF4E binding sequence. eIF4G601‐1196 binds BTE as efficiently as wild type eIF4G and supports translation. Translation initiation factor eIF4A and eIF4B with ATP (helicase complex) stimulate eIF4G601‐1196 binding with BTE but not eIF4G601‐1488, suggesting that the helicase complex function relies on the eIF4G central eIF4A binding domain, not the C‐terminal eIF4A binding domain. eIF4E, upon binding with eIF4G mutants which have eIF4E binding region, significantly increases the binding to BTE. These data suggest eIF4E has a significant role in eIF4G‐RNA binding even in the absence of the cap structure.Support or Funding InformationNSF MCB 1513737