Different forms of p53 detected by monoclonal antibodies in non-dividing and dividing lymphocytes

The commitment of non-dividing cells (in G0) to enter division can be studied using primary cultures of lymphocytes. The cells are stable in G0 unless stimulated by mitogen such as concanavalin A (Con A). Commitment to enter the division cycle depends on the expression of gene(s) induced by Con A and the synthesis of p53 protein correlates with this commitment step. I show here that in unstimulated cells, a second form of p53 is synthesized and is restricted to G0.