Two cellular proteins that are precipitated by an antitumor-RSV rat serum

Here we report studies on non-viral proteins specific for transformation precipitated by immune sera. These sera were from rats injected by PR-RSV transformed rat XC cells and from rabbits immunized by subcutaneous injections of cytoplasmic membranes from rat cells transformed by Fujinami avian sarcoma virus. Immune complexes were analyzed in one- or two-dimensional gel electrophoresis and by autoradiography. Only by using antisera obtained from rats bearing XC-cells induced tumors, two proteins were identified with an apparent molecular weight (Mr) of 105 000 (p105) and 98 000 (p98) and an isoelectric point of 6.4 and 6.2, respectively, in extracts of mammalian cells transformed by avian sarcoma viruses (ASV). These proteins were common to all ASV-transformed cell lines. In kinase reaction, the protein p98 can be phosphorylated. Similar proteins were neither detected in normal nor in chemically transformed cells. None of the proteins were precipitated with control serum from rat, rabbit, and goat.