POLIOVIRUS INFECTION RESULTS IN STRUCTURAL ALTERATION OF A MICROTUBULE-ASSOCIATED PROTEIN

Poliovirus infection results in profound changes in cellular metabolism and architecture. To identify alterations in cellular proteins following poliovirus infection which might account for these changes, monoclonal antibodies were prepared by screening for differences in antigen pattern in infected and uninfected cell lysates. Further characterization of the antigen of one such antibody (25 C Cl) is described in this report. The 25 C C1 antigen is a cytoskeleton-associated protein which decreases in size 4 to 5 h postinfection. It copurifies with some of the protein synthesis initiation factors but not with eucaryotic initiation factor (eIF)-4F, the p220 subunit of which is cleaved following infection (D. Etchison, S. C. Milburn, I. Edery, N. Sonenberg, and J. W. B. Hershey, J. Biol. Chem. 257:14806-14810, 1982). Unlike alteration of p220, alteration of the 25 C C1 antigen is not due to a protease which can be detected by cell lysate mixing experiments. Alteration of the antigen occurs during purification, suggesting progressive proteolysis, but the alteration is more extensive in preparations from infected cells than in those from uninfected cells. A recombinant phage expressing the antigenic determinant was isolated from a human fibroblast cDNA library, and the sequence of the cDNA insert was found to be entirely contained within the established sequence of microtubule-associated protein (MAP) 4 (R. R. West, K. M. Tenbarge, and J. B. Olmsted, J. Biol. Chem. 266:21886-21896, 1991). The antigen distribution, as detected by indirect immunofluorescence, was similar to, but more diffuse than, the distribution of tubulin. The antibody recognized the largest abundant HeLa cell MAP, which copurified with tubulin after three cycles of polymerization-depolymerization, thus confirming the identity of the antigen as MAP 4. These results indicate that poliovirus infection of HeLa cells affects the structural integrity of a cytoskeletal protein, MAP 4.