Characterization of a Nuclear Antigen (Mr 150,000) Associated with Cell Proliferation1

In the course of development of a "library" of monoclonal antibodies to nucleolar proteins, a monoclonal antibody to a nuclear antigen with a molecular weight of 150,000 was obtained. Using this monoclonal anti body as an immunocytochemical probe, low immunofluorescence was demonstrated in human peripheral blood lymphocytes or HL-60 cells treated with retinole acid. In contrast, a high degree of immunofluores cence was detected in rapidly proliferating human cells (HeLa, Hep-2, HL-60), in Novikoff hepatoma cells, and in phytohemagglutinin-activated human blood lymphocytes. Immunodot blot analysis indicated there were low levels of M, 150,000 protein in quiescent lymphocytes and increasing amounts after stimulation with phytohemagglutinin. The increased level of M, 150,000 protein thus is associated with cell proliferation.