2 FUNCTIONAL ASSAYS EMPLOYED TO DETECT AN UNUSUAL MUTATION IN THE OLIGOMERIZATION DOMAIN OF P53 IN A LI-FRAUMENI LIKE FAMILY

Previous investigations of a Li-Fraumeni like family (Barnes et al., 1 992) demonstrated that both the proband and her mother had elevated p5 3 protein levels in both tumour tissue and normal tissue at sites dist ant from the tumour, although no mutation was found in the p53 gene, I n the present study two recently described functional assays for p53, an apoptotic assay and the functional assay for the separation of alle les in yeast (FASAY), have been employed to study the functional activ ity of p53 from this patient, The results of the apoptotic assay demon strated that this patient had a p53 functional defect and the FASAY re sult suggested that this defect was in fact a germline mutation of the p53 gene, A point mutation of codon 337, which results in an amino ac id substitution of a cysteine for an arginine, was demonstrated initia lly in cDNA and was confirmed by sequencing of genomic DNA, This is an unusual mutation as it is in the oligomerisation domain of p53, in co ntrast to the majority of p53 mutations which are in the core DNA bind ing domain, This mutation results in a protein which still retains par tial transactivational activity in the FASAY, The mutation of codon 33 7 is only the second reported case of a germline missense mutation occ urring in the oligomerisation domain of p53.