SPECIFIC DNA-BINDING BY DIFFERENT CLASSES OF HUMAN P53 MUTANTS

The p53 protein is a multifunctional transcription factor which orches trates cellular responses to DNA damage, so helping to conserve genomi c stability. It may also regulate genes involved in intercellular sign alling, such as thrombospondin, a negative regulator of angiogenesis a nd metastatic spread. Activation of p53 target genes requires sequence -specific DNA binding, a function which maps to the central core of th e protein. Missense point mutations within this domain inactivate p53 tumour suppressor function and involve either (i) DNA contact residues , or (ii) residues important for conformational structure. Using in vi tro techniques we have analysed seven DNA contact mutants and 17 struc tural mutants known to occur in cancer. We show that DNA contact mutan ts can be carried into specific DNA interaction when co-expressed with wild type protein. For structural mutants, 9/17 retained DNA binding capacity and, with one exception, DNA binding correlated with conforma tional flexibility of the mutant protein. The exception was Asp(281), which appeared essential for DNA interaction, probably due to its abil ity to form salt bridges with DNA contact residues Arg(273) and Arg(28 0). We suggest that different classes of p53 mutant may prove amenable to different strategies for restoration of wild type tumour suppresso r function as means of anti-cancer therapy.