Inhibition of HeLa cell protein synthesis following poliovirus infection correlates with the proteolysis of a 220,000-dalton polypeptide associated with eucaryotic initiation factor 3 and a cap binding protein complex.

Following poliovirus infection of HeLa cells, the synthesis of cellular proteins is inhibited but translation of poliovirus mRNA proceeds. The defect in the recognition of host cell mRNA may be due to a change in a cap recognition complex which, when added to an infected cell lysate, restores the ability to translate capped mRNAs. We employed immunoblotting techniques to examine initiation factors in crude lysates from uninfected and poliovirus-infected HeLa cells. Using an antiserum against eucaryotic initiation factor 3, we detected an antigen of approximate molecular weight 220,000 in uninfected cell lysates but not in infected cell lysates. Antigenically related polypeptides of 100,000 to 130,000 daltons, presumably degradation products, were detected in the infected cell lysate. The time course for degradation of the 220,000-dalton polypeptide correlates with that for inhibition of cellular protein synthesis in vivo. A portion of the population of 220,000-dalton polypeptides apparently associates with initiation factor eIF3 but is readily dissociated in buffers containing high salt. Affinity-purified antibodies against the polypeptide recognize a protein of the same size in a purified preparation of a cap binding protein complex obtained by cap-affinity chromatography. We postulate that the 220,000-dalton polypeptide is an essential component of the cap recognition complex and that its degradation in poliovirus-infected cells results in the inhibition of host cell translation. These results are in the first demonstration of a specific structural defect in an initiation factor resulting from poliovirus infection.