Identification of a new, abundant superfamily of mammalian LTR-transposons.
A new superfamily of mammalian transposable genetic elements is described with an estimated 40,000 to 100,000 members in both primate and rodent genomes. Sequences known before as MT, ORR-1, MstII, MER15 and MER18 are shown to represent (part of) the long terminal repeats of retrotransposon-like elements related to THE1 in humans. These transposons have structural similarities to retroviruses. However, the putative product of a 1350 base pair open reading frame detected in the consensus internal sequence of THE1 does not resemble retroviral proteins. The elements are named 'Mammalian apparent LTR-retrotransposons' (MaLRs). The internal sequence is usually found to be excised. Their presence in rodents, artiodactyls, lagomorphs, and primates, the divergence of the individual elements from their consensus, and the existence of a probably orthologous element in mouse and man suggest that the first MaLRs were distributed before the radiation of eutherian mammals 80-100 million years ago. MaLRs may prove to be very helpful in determining the evolutionary branching pattern of mammalian orders and suborders.
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Department of Biology, Beckman Research Institute of the City of Hope, Duarte, CA 91010-0269.
D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D006224:Cricetinae; D004247:DNA; D004251:DNA Transposable Elements; D006801:Humans; D008322:Mammals / Q000235:genetics*; D008969:Molecular Sequence Data; D012091:Repetitive Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid
D004251:DNA Transposable Elements; D004247:DNA