Structure and activities of the ski oncogene.

The ski oncogene is the transforming gene, v-ski, of the defective SKV avian carcinoma viruses. V-ski transformation causes increased proliferation of embryo fibroblasts and also induces a number of genes characteristic of the muscle lineage. In natural SKV isolates the 49 kDa v-ski polypeptide is expressed as a fusion protein with N-terminal gag and other viral sequences. The cellular homologue of v-ski, c-ski, is a large gene comprising at least 70 kb and containing at least seven coding exons. V-ski consists of most of the first five coding exons of c-ski. The proteins encoded by both genes are nuclear proteins that bind DNA and contain recognised motifs common to known nuclear regulatory proteins. A c-ski-related gene called sno has also been recently identified and, like c-ski, it is expressed in several human tumour cell lines.