title: Evidence for dynamic alteration in histone gene clusters of Caenorhabditis elegans: a topoisomerase II connection?
abstract: Chromatin integrity is maintained throughout the cell cycle through repair mechanisms and intrinsically by the ordered packaging of DNA in association with histone proteins; however, aberrant rearrangements within and between chromosomes do occur. The role of the nuclear matrix protein topoisomerase II (TopoII) in generating chromosome breakpoints has been a focus of recent investigations. TopoII preferentially binds in vitro to scaffold-associated regions (SARs) and is involved in many DNA processing activities that require chromosome untangling. SARs, biochemically defined DNA elements rich in A + T, have been proposed to serve as structural boundaries for chromatin loops and to delineate functional domains. In our investigation of gene compartmentalization in a eukaryotic genome, SAR-associated nucleotide motifs from Drosophila were mapped in the regions of three histone gene clusters in an in silico analysis of the genome of Caenorhabditis elegans. Sites with similarity to the 15 bp consensus for TopoII cleavage were found predominantly in A + T enriched intergenic regions. Reiteration of sites matching the TopoII core consensus led to the identification of a novel core histone gene on chromosome IV and provided evidence for duplication and inversion in each of the three histone gene clusters. Breakpoint analysis of DNA flanking reiterated regions revealed potential sites for TopoII cleavage and a base composition phenomenon suggestive of a trigger for inversion events.
authors.affiliation: Division of Biological Sciences, University of Missouri, 312 Tucker Hall, Columbia, Missouri 65211-7400, USA.
authors.forename: Suzan J
authors.initials: SJ
authors.lastname: Holt
authors.forename: William A
authors.initials: WA
authors.lastname: Cress
authors.forename: Johannes
authors.initials: J
authors.lastname: Van Staden
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics*; D007446:Chromosome Inversion; D004250:DNA Topoisomerases, Type II / Q000235:genetics*; D019143:Evolution, Molecular; D006657:Histones / Q000235:genetics*; D008969:Molecular Sequence Data; D005810:Multigene Family; D017422:Sequence Analysis, DNA
chemical_list: D006657:Histones; D004250:DNA Topoisomerases, Type II