Tissue specificity and cellular distribution of Novikoff hepatoma antigenic proteins p39, p49, and p56.

Three Novikoff hepatoma protein antigens (approximately Mr = 39,000, 49,000, and 56,000) were partially purified from Novikoff hepatoma chromatin. Rabbit antiserum to these three proteins was used to examine various rat tissues for the presence of these antigens. Immunological specificity of the antiserum was assessed using quantitative microcomplement fixation assay or by visualization of the immunoreactive complexes with peroxidase-antiperoxidase procedure after transferring the electrophoretically separated proteins to nitrocellulose sheets. The immunoreactivity was localized with the three proteins p39, p49, and p56 in Novikoff hepatoma. The p56 protein was found to be present in normal rat liver, 24-h regenerating rat liver, fetal rat liver, or kidney, albeit in much smaller amounts as found in Novikoff hepatoma. the p49 and p39 antigens were specific for Novikoff hepatoma. Immunoabsorption experiments confirmed the specificity of this antiserum. Assessment of various subcellular fractions of Novikoff hepatoma revealed that the p39, p49, and p56 protein antigens are present in the cytoplasmic fractions as well as in isolated chromatin.