Biological and biochemical characterization of a new isolate of feline sarcoma virus: Theilen-Pedersen (TP1-FeSV).

A new feline sarcoma virus designated Theilen-Pedersen (TP1-FeSV) has been isolated from a spontaneous, slowly growing fibrosarcoma of a domestic short-haired 4-year-old castrated cat. The virus codes for a gag-onc fusion protein of 83,000 molecular weight phosphorylated in vivo at serine, threonine, and tyrosine residues. Cells transformed in vitro with TP1-FeSV exhibit five- to 10-fold elevated levels of phosphotyrosine over FeLV-infected cells. The gag-onc polyprotein has associated with it a tyrosyl protein kinase activity which in vitro results in autophosphorylation of the molecule at tyrosine residues. The fusion protein cannot be labeled metabolically with [3H]glucosamine and tunicamycin has no effect on the electrophoretic mobility of the in vivo [32P]orthophosphate-labeled fusion protein. The fusion protein, in common with the gag precursor Pr65gag, can be metabolically labeled with palmitic acid.