Identification of a nuclear antigen with molecular weight of 48 000 differentially expressed in tumour and normal cells

A non‐histone protein with mol. wt of 48 000 differentially expressed in normal and tumour cells was identified using immunological criteria. Antibodies were raised against a component specific for Kirkman‐Robbins hepatoma of mol. wt about 48 000 separated from hepatoma non‐histone proteins by preparative electrophoresis in polyacrylamide gel. It was demonstrated by immunoblotting that Morris hepatoma 7777 and Ehrlich ascites cells share an antigenic non‐histone protein with Kirman‐Robbins hepatoma. Tumour cells when compared with normal cells, i.e. hamster and rat liver, are characterized by significant enrichment of this component. Intracellular distribution of the polypeptide with mol. wt 48 000 suggests that this component may be a structural protein the biosynthesis of which increases or the antigenic determinants of which change in tumour cells.