Continued presence of similar transformation-associated antigens related to murine oncornavirus proteins in -ransformed cells, morphological revertants, and cells restricted in the expression of transformation.

The possible alteration of transformation-related antigens in cells that revert to a normal phenotype but that continue to retain the viral genome, has been investigated in [3H]glucosamine-labeled extracts of rat cells exhibiting a reversible temperature-dependent restriction in the expression of transformation and in a comparison of a morphologically altered mouse cell transformed by the Kirsten sarcoma virus with a flat revertant mouse cell derived from the morphologically transformed cells. With the use of normal goat serum in the presence of dibutyryl cyclic 3':5'-adenosine monophosphate, some differences became obvious in the rat cells restricted in the expression of transformation. However, use of specific antiserum to murine leukemia virus revealed in every case the presence of major components that exhibited an electrophoretic mobility corresponding to about 100,000 daltons both in the parent and revertant mouse cells and in the rat cells exhibiting either untransformed or transformed growth properties. The glycoprotein components detected only by the immune serum may represent a cellular macromolecule antigenically related to an interspecies C-type viral species whose concentration is increased in transformed cells.