title: Co-localization of centromere activity, proteins and topoisomerase II within a subdomain of the major human X alpha-satellite array.
abstract: Dissection of human centromeres is difficult because of the lack of landmarks within highly repeated DNA. We have systematically manipulated a single human X centromere generating a large series of deletion derivatives, which have been examined at four levels: linear DNA structure; the distribution of constitutive centromere proteins; topoisomerase IIalpha cleavage activity; and mitotic stability. We have determined that the human X major alpha-satellite locus, DXZ1, is asymmetrically organized with an active subdomain anchored approximately 150 kb in from the Xp-edge. We demonstrate a major site of topoisomerase II cleavage within this domain that can shift if juxtaposed with a telomere, suggesting that this enzyme recognizes an epigenetic determinant within the DXZ1 chromatin. The observation that the only part of the DXZ1 locus shared by all deletion derivatives is a highly restricted region of <50 kb, which coincides with the topo isomerase II cleavage site, together with the high levels of cleavage detected, identify topoisomerase II as a major player in centromere biology.
mesh_terms: D000951:Antigens, Neoplasm; D001483:Base Sequence; D002460:Cell Line; D002503:Centromere / Q000235:genetics* / Q000502:physiology; D002874:Chromosome Mapping; D041321:Chromosomes, Human, X / Q000235:genetics* / Q000648:ultrastructure; D017931:DNA Primers; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D004268:DNA-Binding Proteins; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction / Q000379:methods; D015183:Restriction Mapping; D014162:Transfection
chemical_list: D000951:Antigens, Neoplasm; D017931:DNA Primers; D004268:DNA-Binding Proteins; D004250:DNA Topoisomerases, Type II