ACTIVATION OF THE CRYPTIC DNA-BINDING FUNCTION OF MUTANT FORMS OF P53

Wild type p53 assembles into a latent multiprotein complex which can b e activated for sequence-specific DNA binding in vitro by proteins tar geting the carboxy-terminal domain. Using an optimized system coupling the post-translational modification of wild type p53 to activation of sequence specific DNA binding, we examined the affects of common muta tions on the cryptic DNA binding function of p53. Two mutant forms of p53 were shown to be efficiently converted from the latent state by PA b421 and DnaK, but were defective in activation by casein kinase II, i ndicating that mutant p53 may not be receptive to allosteric regulatio n by casein kinase II phosphorylation. A reactive sulfhydryl group is absolutely required for DNA binding by wild type and mutant forms of p 53 once converted to the activated state. Together, these data show th at some mutant forms of p53 harbour the wild-type machinery required t o engage in sequence-specific DNA binding and define a signalling path way whose inactivation may directly result in a loss of p53 function.