The solubility characteristics of SV 40 tumor antigen

The solubility characteristics of SV40 tumor (T) antigen were investigated. Cell nuclei were isolated from cover glass cultures of SV 40-infected or transformed cells by detergent treatment. When treated in a buffered isotonic sucrose solution, the isolated nuclei contained typical SV40 T antigen by immunofluorescence. If the detergent was dissolved in an isotonic electrolyte solution containing 0.15 M monovalent cations (K+), the T antigen was extracted from the nuclei. Complement fixation tests demonstrated that the various solutions had no deleterious effects on the antigenicity of T antigen. Under identical conditions, the SV 40 capsid (V) antigen was not extracted from infected cell nuclei. These solubility characteristics place SV40 T antigen in the class of “loosely bound” nuclear proteins which includes non-histone proteins that appear to have cell regulatory functions. This supports the suggestion that the biological function of T antigen may be regulatory in nature.