COMPARISON OF REPETITIVE ELEMENTS IN THE 3RD INTRON OF HUMAN AND RODENT MITOCHONDRIAL BENZODIAZEPINE RECEPTOR-ENCODING GENES

The third intron of the mitochondrial benzodiazepine receptor (MBR)-en coding gene was sequenced from hamster, mouse and human. The rodent sp ecies were found to include an Alu-like sequence, as was first discove red in the rat gene, Differences with the rat intron were evident by a n insertion of an additional B1 element in the hamster and the introdu ction of a complete and two partial B2 sequences in the mouse intron. The human intron contained a cluster of four Alu sequences; however, a ll of these repetitive elements were found to be in the opposite orien tation relative to the Alu-like sequence present in the rodent genes, These findings support the possibility that the rodent Alu-like sequen ce is a remnant of a retropositional insertion in this gene prior to t he divergence of rodent species. Because the human intron does not con tain the same Alu remnant, it cannot be concluded that the rodent sequ ence represents an insertion of a primordial Alu element prior to the divergence of rodent and primate lineages.