Characterization of the chimeric SV40 large T antigen which has a membrane attachment sequence of polyoma virus middle T antigen.

A chimeric SV40 mutant, pMTPY, was constructed which codes for a large T antigen having the putative membrane attachment sites of polyoma virus middle T antigen at the carboxy-terminal portion. The mutant T antigen was detected exclusively in the cytoplasm of CV-1 cells transfected with pMTPY by a fluorescent antibody test. This mutant could not support viral DNA replication, but could immortalize secondary cultured rat brain (RB) cells. Immortalized RB cells produced nonkaryophilic large T antigen and also small T antigen. The amount of p53 expressed in those cells was larger than that in control RB cells. In addition, this mutant had the ability to transform NIH3T3 cells. The mutant nonkaryophilic large T antigen in NIH3T3 transformant was localized in cytoplasmic membrane fractions.