Characterization of nonautonomous Tc1-like transposable elements of channel catfish (Ictalurus punctatus)

Putative nonautonomous transposable elements from channel catfish (Ictaluru s punctatus) were identified. They were named Tipnon elements for Tc1-like transposable elements from channel catfish that are nonautonomous. These el ements were defined by their terminal repeats that share identity to member s of the known Tc1/mariner transposon superfamily. They show structural sim ilarities to Tc1-like elements, but share little sequence identity beyond t he terminal inverted repeats. They do not harbor any amino acid blocks that show similarities to the Tc1-like or other transposases and thus may repre sent truly nonautonomous transposons in channel catfish. They are abundant in the channel catfish genome with a copy number of 32 000, having 500 base pair per copy, this family of nonautonomous transposon-like elements accou nt for 1.6% of the channel catfish genomic DNA. Their high abundance and tr ansposon-like terminal repeats indicate that they may play important roles in gene evolution and in genomic architecture of catfish. Similarity search for potential coding capacity of the Tipnon elements revealed that they co ntain sequence blocks that can potentially encode amino acid blocks similar to the para-type sodium channel proteins in cockroaches or house flies, pr oteins that function in the central nervous system as voltage-gated sodium transporters. Sequences surrounding the terminal inverted repeats are diver gent from those used by the reconstructed Sleeping Beauty fish transposase.