THE EFFECT OF PHOSPHORYLATION ON THE ANTIGENIC REACTIVITY OF P53 IN CULTURED HUMAN KERATINOCYTES

The detection of p53 in human keratinocytes is dependent on the specif ic anti-p53 monoclonal antibody that is used. Differences in antibody recognition are postulated to be due to the masking or exposure of par ticular epitopes in different conformations of p53. This study address es the role of phosphorylation on p53-epitope accessibility in human k eratinocytes. Keratinocytes were treated with the phosphatase inhibito r, okadaic acid, to determine the effect of inhibiting cellular phosph atases on p53 phosphorylation and epitope recognition. These studies s uggest there is a correlation between the level of p53 phosphorylation and the antigenic reactivity of certain p53 epitopes in human keratin ocytes. We also examined the ability of the catalytic subunits of prot ein phosphatase 1 and 2A to dephosphorylate p53 derived from human ker atinocytes in vitro. These data suggest that PP2A may be the phosphata se that acts on p53 in cultured human keratinocytes. (C) 1995 Academic Press, Inc.