Relationship of the feline oncornavirus associated cell membrane antigen to a feline sarcoma virus encoded polyprotein.

The feline oncornavirus associated cell membrane antigen (FOCMA) is expressed on the membranes of cells transformed by infection with the feline leukemia virus (FOCMA-L) or feline sarcoma virus (FOCMA-S) (Hardy et al. 1977; Essex et al. 1977). Expression of FOCMA is transformation-specific and not dependent upon concomitant expression of antigens associated with feline leukemia virus (FeLV) or the endogenous virus RD114 (reviewed in Snyder et al., to be published a). In the natural environment FOCMA is the target for an effective immunosurveillance response: complement-dependent lytic antibodies directed to FOCMA reverse or prevent tumor development (Essex et al. 1975; Grant et al. 1977). FOCMA-L has been isolated from feline lymphosarcoma (LSA) cell membranes and has been shown to reside on a 70,000 dalton pro tein which is neither glycosylated nor phosphorylated (Snyder et al. 1978, to be published a). The nature of FOCMA-S is a subject of intense investigation at the present time. The observation that FOCMA is induced on FeSV -transformed nonproducer fibroblasts of nonfeline as weIl as feline origin has been interpreted as evidence that FOCMA-S may actually be encoded by FeSV (Essex et al. 1979). Present evidence suggests that in the derivation of the defective FeSV genome sequences from the pol and the 3' end of the gag and env genes were deleted and the gag-pol deletion was substituted with cat cellular DNA sequences which contain information for transformation (Frankel et al. 1979; Sherr et al. 1980). The translation products of FeSV genomes in nonproducer