Specificity of DNA-associated nuclear antigens in HeLa cells and distribution during the cell cycle

Chromosomal nonhistone protein:DNA complexes prepared from synchronized HeLa cells were used to immunize white rabbits. The antisera reacted specifically in complement fixation tests with chromatins isolated from HeLa cells and not with those from a number of other human and animal tissues. Specificity to this cell type was also demonstrated by immunocytochemical reaction. Both immunochemical tests revealed that the specific antigens are continuously present throughout the cell cycle. The immunological activity was dependent upon chromosomal nonhistone protein(s) being bound to DNA. Our findings are consistent with these chromatin antigens being stable nuclear components [complexes of chromosomal non-histone protein(s) with DNA] characteristic of cellular differentiation.