FIG. 4.

Binding of Giardia eIF4E1 and eIF4E2 to different cap structures. (A) HA-tagged eIF4E1 eluted through a m⁷GTP-Sepharose column was analyzed by immunoblotting (Fig. 2B), and the result demonstrated no detectable binding between the protein and the cap. (B) c-myc-tagged eIF4E2 applied to an m⁷GTP-Sepharose column showed that it was bound to the cap structure. (C) c-myc-tagged eIF4E1 was mixed with a biotinylated RNA species capped with m^2,2,7GpppG and subjected to a pulldown experiment with streptavidin-agarose beads. The results from the subsequent immunoblotting indicated that the protein was pulled down with the beads and was released only by washing with m^2,2,7GpppG. (D) In a similar experiment, c-myc-tagged eIF4E1 was not brought down by the m⁷GpppG-capped RNA.