HUMAN PROTEIN SAM68 RELOCALIZATION AND INTERACTION WITH POLIOVIRUS RNA-POLYMERASE IN INFECTED-CELLS

A HeLa cDNA expression library was screened for human polypeptides tha t interacted with the poliovirus RNA dependent RNA polymerase, 3D, usi ng the two-hybrid system in the yeast Saccharomyces cerevisiae, Sam68 (Src-associated in mitosis, 68 kDa) emerged as the human cDNA that, wh en fused to a transcriptional activation domain, gave the strongest 3D interaction signal with a LexA-3D hybrid protein. 3D polymerase and S am68 coimmunoprecipitated from infected human cell lysates with antibo dies that recognized either protein, Upon poliovirus infection, Sam68 relocalized from the nucleus to the cytoplasm, where poliovirus replic ation occurs. Sam68 was isolated from infected cell lysates with an an tibody that recognizes poliovirus protein 2C, suggesting that it is fo und on poliovirus-induced membranes upon which viral RNA synthesis occ urs. These data, in combination with the known RNA- and protein-bindin g properties of Sam68, make Sam68 a strong candidate for a host protei n with a functional role in poliovirus replication.