ISOLATION OF CANINE P53 CDNA AND DETAILED CHARACTERIZATION OF THE FULL-LENGTH CANINE P53 PROTEIN

The p53 tumour suppressor protein plays a central role in the maintena nce of genomic integrity. Mutations of the p53 gene are found in a num ber of canine cancers and many contribute to tumour formation, Here we describe isolation and expression of the complete wild type canine p5 3 cDNA. The encoded full length canine p53 protein displays strong seq uence homology with p53 proteins from other higher vertebrates, Canine p53 protein produced in vitro was shown to recognize and bind to p53- specific DNA targets derived from the p21 and GADD45 promoters and to a consensus p53 binding site, We also show that canine p53 associates with oligonucleotides representing damaged DNA sites and undergoes pro teolytic cleavage similar to that described for murine and human p53 p roteins. Finally, we show that the canine p53 protein is able to trans criptionally activate a p53-dependent reporter gene in vivo, The resul ts suggest that canine p53 is similar both in structure and function t o human p53 and that canine cancer may provide a useful clinical model in the search for effective anti-cancer therapies based on p53.