GENOMIC STRUCTURE OF C-KI-RAS PROTOONCOGENE OF THE HERMAPHRODITIC FISH RIVULUS-MARMORATUS (TELEOSTEI, RIVULIDAE)

The ras homologue of the rivulid fish Rivulus marmoratus was isolated and characterized by screening about 3.0 x 10(5) genomic clones from a Rivulus genomic library using human c-Ha-ras probe. When this clone w as partially sequenced focusing on the region coding exons, it showed 97.5% amino acid homology to the human c-Ki-ras gene. The Rivulus c-Ki -ras gene spans about 6.3 kb and consists of five exons including the alternative splicing exon 4a/4b. The exon-intron boundaries of Rivulus c-Ki-ras gene coincided with the GT/AG rule of consensus splice accep tor and donor sequences as in mammalian c-Ki-ras genes. Amino acid seq uence analysis of some domain regions of the Rivulus c-Ki-ras gene rev ealed 100% identity to mammalian c-Ki-ras gene. This report is the fir st that elucidate the entire structure of c-Ki-ras in a fish.