Evolutionary implications of multiple SINE insertions in an intronic region from diverse mammals |
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Authors: | Li Yu Ya-ping Zhang |
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Institution: | (1) Laboratory of Molecular Biology of Domestic Animals, and Cellular and Molecular Evolution, Kunming Institute of Zoology, Kunming, 650223, China;(2) Laboratory for Conservation and Utilization of Bio-resource, Yunnan University, Kunming, 650091, China;(3) Graduate School, Chinese Academy of Sciences, Beijing |
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Abstract: | An analysis of the nuclear β-fibrinogen intron 7 locus from 30 taxa representing 12 placental orders of mammals reveals the
enriched occurrences of short interspersed element (SINE) insertion events. Mammalian-wide interspersed repeats (MIRs) are
present at orthologous sites of all examined species except those in the order Rodentia. The higher substitution rate in mouse
and a rare MIR deletion from rat account for the absence of MIR in the rodents. A minimum of five lineage-specific SINE sequences
are also found to have independently inserted into this intron in Carnivora, Artiodactyla and Lagomorpha. In the case of Carnivora,
the unique amplification pattern of order-specific CAN SINE provides important evidence for the “pan-carnivore” hypothesis
of this repeat element and reveals that the CAN SINE family may still be active today. Particularly interesting is the finding
that all identified lineage-specific SINE elements show a strong tendency to insert within or in very close proximity to the
preexisting MIRs for their efficient integrations, suggesting that the MIR element is a hot spot for successive insertions
of other SINEs. The unexpected MIR excision as a result of a random deletion in the rat intron locus and the non-random site
targeting detected by this study indicate that SINEs actually have a greater insertional flexibility and regional specificity
than had previously been recognized. Implications for SINE sequence evolution upon and following integration, as well as the
fascinating interactions between retroposons and the host genomes are discussed. |
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