Characterization of a swine chromosome-specific centromeric higher-order repeat |
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Authors: | MA Janzen LB Buoen F Zhao CF Louis |
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Institution: | (1) Department of Biochemistry, University of Minnesota, St. Paul, Minnesota 55108, USA, US;(2) Department of Veterinary Diagnostic Medicine, University of Minnesota, St. Paul, Minnesota 55108, USA, US;(3) Department of Veterinary Pathobiology, University of Minnesota, 1988 Fitch Ave., Room 295, St. Paul, Minnesota 55108, USA, US |
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Abstract: | The centromeric region of swine chromosomes is comprised of tandemly repeated, divergent DNA monomer units. Here we report
that these divergent DNA monomer sequences are organized into higher-order repeats, analogous to the hierarchical organization
of α-satellite monomers in human centromeres. In this study, a centromeric cosmid clone was shown to be comprised entirely
of a 3.3-kb higher-order repeat, with independent copies of this higher-order repeat more than 99% identical to each other.
This higher-order repeat is composed of ten divergent monomer units of approximately 340 bp. The ten monomers are on average
79% identical, and all ten monomers are arranged in the same 5′ to 3′ orientation. In FISH analysis, a cloned 3.3-kb higher-order
repeat hybridized to the centromere of Chromosome (Chr) 9 in metaphase spreads and detected two discrete foci in interphase
nuclei, demonstrating that this swine higher-order repeat is chromosome-specific. The Chr 9 centromeric array spanned approximately
2.2 Mb as determined by pulsed-field gel electrophoresis. Moreover, the swine Chr 9 centromere is highly polymorphic, because
an EcoRI restriction site polymorphism was detected. Thus, the assembly of divergent satellite sequences into chromosome-specific
higher-order repeats appears to be a common organizational feature of both the human and swine centromere and suggests that
the evolutionary mechanism(s) that create and maintain higher-order repeats is conserved between their genomes.
Received: 6 August 1998 / Accepted: 20 January 1999 |
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