Characterization of a swine chromosome-specific centromeric higher-order repeat.
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 alpha-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.
Janzen
M A
MA
Department of Biochemistry, University of Minnesota, St. Paul, Minnesota 55108, USA.
Buoen
L B
LB
Zhao
F
F
Louis
C F
CF
D000818:Animals; D001483:Base Sequence; D002503:Centromere / Q000235:genetics*; D002875:Chromosomes; D003001:Cloning, Molecular; D003360:Cosmids / Q000235:genetics; D015252:Deoxyribonucleases, Type II Site-Specific / Q000235:genetics / Q000378:metabolism; D016678:Genome; D017404:In Situ Hybridization, Fluorescence; D007399:Interphase / Q000235:genetics; D008969:Molecular Sequence Data; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D013552:Swine / Q000235:genetics*
C024408:endodeoxyribonuclease SacI; D015252:Deoxyribonucleases, Type II Site-Specific