CLONING AND SEQUENCING OF CATR1.3, A HUMAN GENE ASSOCIATED WITH TUMORIGENIC CONVERSION

The human squamous cell carcinoma cell line SCC83-01-82 (SCC) contains mutations in both the H-ras and p53 genes, but it exhibits a nontumor igenic phenotype in nude mice, This cell line can be converted into a cell line with a tumorigenic phenotype, SCC83-01-82CA (CA), by treatme nt with the mutagen methyl methanesulfonate (MMS), This indicates that additional genetic events leading to expression of a cooperating tumo r susceptibility gene(s) may be required for tumorigenicity, To identi fy the cooperating gene(s), an expression cDNA library was made from t umorigenic CA cells, The library DNA was transfected into nontumorigen ic SCC cells and the transfected SCC cells were then injected into nud e mice for the selection of a tumorigenic phenotype, Tumors developed in 3 of the 18 mice after injection. Several new cell lines were estab lished from these transfected cell-induced tumors and designated as CA TR cells, Tumor histology and karyotype analysis of these cells indica ted that they were of human epithelial cell origin, All the CATR cells have the library vector sequence integrated in their genome, Cell lin e CATR1 expressed a single message from the integrated library represe nting a 1,3-kb cDNA insert that was absent from untransfected SCC cell s or MMS-converted CA cells, This 1,3-kb cDNA insert was cloned by PCR amplification of reverse-transcribed CATR1 total RNA and was designat ed CATR1.3. The nucleotide sequence of CATR1,3 encodes a peptide of 79 amino acids, has a long 3' untranslated region, and represents an unk nown gene product that was associated with the tumorigenic conversion due to the transfected expression library.