Biopolymers and cell. 1999; 15 (6): 529 - 537

The analysis of chum salmon insulin-like growth factor I gene sequence: transposones

V. A. Grebenjuk

Most vertebrates genome contains multiple copies of Tel-like transposones. Waste majority of them localized in non-expressed part of the genome. Two Tel-like transposones, designated Tokl and Tok2 are found in the same orientation in the second and third introns of chum salmon IGF-J gene. Phylogenetic analysis placed them to salmon SALT(Tss2) and zebrafish Tdr2(Tzf) cluster. The transposase ORFs contain multiple frameshifts and stop codons and have the same orientation in both transposones, but opposite to the ICF-I gene flow. Existence of Tok2 in third introns of both nonaUe.Lic salmon JGF-I genes and absence of similar transposones in IGF-l genes of other fish species (perch, zunder, pike, tilapia) apparently shows that they appeared in fish IGF-1 gene after the salmonid branching from common ancestor, but before the tetra-ploidizalion event. Position of mobile elements in IGF-I gene and the existence in salmon genome expressed sequences, framed by the same or homologous elements, makes possible to suspect the transposition of the exones or genes by the cassette of two transposones. Such transposition, well known in invertebrates, may also exists in vertebrates.