Tumor Suppressor Protein p53 and its Physiological Splicing Variant p53 as in a Mouse Mammary Cancer Model

摘要

Mouse mammary cell lines containing either wild type or mutant p53 were used to examine distinct p53 forms following treatment with the DNA damaging agents actinomycin D and genistein using immunofluorescence, sequence- specific DNA binding, or western immunoblotting. We show that p53 genotype does not predict p53 response to DNA damage or function. For example, cell lines containing wild type p53 had one of the following three disparate 'molecular phenotypes': (1) p53 expression (TM9) is not induced by genistein treatment and the protein is unable to bind DNA, (2) p53 expression (TM10) is induced by genistein treatment and both active and latent forms are present for DNA binding, and (3) only latent forms (TM12) are available for DNA binding that are not induced by genistein treatment. This variability of induction and activity may depend on p53 associated factors. To examine this possibility, we have isolated mammary specific p53-associated proteins, subjected them to micro sequencing and identified them as three splicing factors and two ribosomal proteins. The DNA binding sequence of the endogenous active form of mouse p53, p53as, has been shown to contain the same hallmarks as that for p53. In addition to the p53 consensus sequence, non-consensus DNA sequences have been confirmed and novel gene targets of p53 suggested.