The p53 tumor suppressor gene of the marsupial Monodelphis domestica: cloning of exons 4-11 and mutations in exons 5-8 in ultraviolet radiation-induced corneal sarcomas

Inactivating p53 mutations are found in many ultraviolet radiation (UVR)-in duced skin tumors. We examined 12 UVR-induced corneal tumors of the marsupi al Monodelphis domestica for mutations in exons 5-8 of p53 and compared the ir mutational spectrum with that of UVR-induced skin tumors of other specie s. First we cloned and characterized a cDNA extending from the middle of ex on 4 through exon 11 of the Monodelphis p53 gene. Based on the sequence inf ormation obtained, primers were designed to amplify introns 4-9 of the gene ; intron primers to amplify individually exons 5-8 were subsequently develo ped,'Cold' single strand conformational polymorphism analysis followed by r eamplification of DNA with altered mobility and cycle sequencing revealed s ingle p53 mutations in four of 12 tumors (33%), including one mutation in e xon 5, two identical mutations in exon 7 and one mutation in exon 8, All mu tations were at dipyrimidine sites and occurred on the non-transcribed stra nd, Three of the four were hallmark UVR-induced C-->T alterations. Three of the mutations were found at sites corresponding to human codons 248 and 27 3, which are mutational hotspots in human and murine UVR-induced squamous c ell carcinomas. Our findings suggest that UVR-induced corneal sarcomas in M onodelphis will be valuable in studying mechanisms of p53 mutation in UVR-i nduced tumors.