EVOLUTION OF BSP REPEATS - FORMATION OF SUBREPEAT AND MONOMER UNITS PRECEDES THE DIVERGENCE OF 4 CANIDAE SPECIES

Primary structures of two cloned fragments of the Bsp repeats of racco on dog (Nyctereutes procyonoides) DNA were compared with the correspon ding DNA homologous sequences of three other Canidae species. It was d emonstrated that Bsp repeat fragments of raccoon dog, dog, silver fox, and grey fox genomes which belong to four out of five phylogenetic li neages of Canidae are composed of five main types of subrepeats (A, B, C, D, and E) and two types of monomers (ACB and ACED). A 1620-bp N. p rocyonoides DNA fragment includes two ACBACED monomers. In ACB and ACE D monomers, the sequences of some subrepeat variants are degenerate. B asing on the dendrogram constructed for 18 DNA subrepeat sequences as well as on the results obtained in the study of higher-level organizat ion of monomer and subrepeat structure, the evolutionary events result ing in the Bsp repeat hierarchy were reconstructed. The number of nucl eotide substitutions in each of dendrogram branches was used to determ ine the time intervals corresponding to these events. The five main ty pes of repeats and two types of monomers seem to have occurred stepwis e and before the divergence of the main phylogenetic Lineages of Canid ae. The hierarchy levels of Bsp repeat structure were mostly formed by combinatorial variability.