Involvement of eukaryotic initiation factor 4A in the cap recognition process.

Antibodies against eukaryotic initiation factor 4A (eIF-4A) were used to study the involvement of this factor in recognizing the 5' cap structure of eukaryotic mRNA. We demonstrate that an approximately 50-kilodalton polypeptide present in rabbit reticulocyte ribosomal high salt wash which can be specifically cross-linked to the 5' oxidized cap structure of reovirus mRNA (Sonenberg, N. (1981) Nucleic Acids Res. 9, 1643) reacts with an anti-eIF-4A monoclonal antibody. We also show that antibodies against eIF-4A react with a 50-kilodalton polypeptide present in a cap-binding protein complex obtained by elution from a m7GTP-agarose affinity column. Comparative peptide analysis of eIF-4A and the 50-kilodalton component of the cap-binding protein complex indicates a very strong similarity between the two polypeptides.