A NEWLY ISOLATED FAMILY OF SHORT INTERSPERSED REPETITIVE ELEMENTS (SINES) IN COREGONID FISHES (WHITEFISH) WITH SEQUENCES THAT ARE ALMOST IDENTICAL TO THOSE OF THE SMAI FAMILY OF REPEATS - POSSIBLE EVIDENCE FORTHE HORIZONTAL TRANSFER OF SINES

The SmaI family of repeats is present only in the chum salmon and the pink salmon, and it is not present in five other species in the same g enus or in other species in closely related genera. In the present stu dy, we showed that another short interspersed repetitive elements (SIN Es) family, which is almost identical to the SmaI family, is present i n all fishes in the subfamily Coregoninae, being regarded as the most primitive salmonids. This new family of SINEs was designated the SmaI- cor family (SmaI family of repeats in coregonids). The consensus seque nce of the SmaI-cor family was found to be 98.6% homologous to that of the SmaI family. Accordingly, it is difficult to explain the high deg ree of homology between these two families of SINEs by any mechanism o ther than the horizontal transfer of SINEs. The estimates of the rate of neutral mutation of nuclear genes, comparing chum salmon and Europe an whitefish, confirmed this possibility. Our results strongly suggest that a member(s) of the SmaI-cor family might have been transferred h orizontally from one coregonid species to a common ancestor of chum an d pink salmon or to these two species independently, to allow subseque nt amplification of the SmaI family in their respective genomes.