FIG. 3.

Enrichment of eIF4B in initiation complexes with IRES RNA by stage-specific translation initiation inhibitors. (A) Gradient profiles. The binding reactions with RRL and labeled IRES-912 RNA were performed as in Fig. 1 (solid line), in the presence of 4 mM GMP-PNP (dashed line), or in the presence of 0.17 mM anisomycin (dotted line). (B) UV-cross-linked proteins from RNase-treated fractions of the gradients shown in panel A were collected by TCA precipitation, resolved on SDS-polyacrylamide gels, and visualized by autoradiography. Molecular masses of marker proteins (M) are given in kilodaltons. 4B, eIF4B.