Figure 1.

G4-tiRNAs directly target eIF4F. (A) Strategy of purification of eIF4F adapted from (16). (B) Purified human eIF4F is sensitive to TOG containing tiRNAs in a G-quadruplex dependent manner. Purified eIF4F was bound to m⁷GTP-agarose and challenged with indicated small RNAs. 5′tiRNA^Ala efficiently disrupted the eIF4F complex, but 5′tiRNA^Ala(daG), which cannot form a G4 efficiently had reduced activity. (C) Schematic of eIF4G indicating domains required for interaction with other proteins (orange), protease cleavage sites (red lines), sites of truncations (black lines). RNA Binding region (red bar) and HEAT1 repeat (green bar) are indicated. (D) Recombinant eIF4G containing the RNA binding region is sensitive to 5′tiRNA^Ala. eIF4E and truncation of eIF4G were expressed and purified from E. coli, bound to m⁷GTP-agarose and challenged with indicated RNAs. 5′tiRNA^Ala could disrupt eIF4F when eIF4G retained the RNA binding regions (90–1129). This disruption was dependent upon G4 formation as 5′tiRNA^Ala(daG) is incapable of disrupting eIF4F.