title: Evidence on the chromosomal location of centromeric DNA in Plasmodium falciparum from etoposide-mediated topoisomerase-II cleavage.
abstract: Centromeres are the chromosomal loci that facilitate segregation, and, in most eukaryotes, they encompass extensive regions of genomic DNA. Topoisomerase-II has been identified as a crucial regulator of segregation in a wide range of organisms and exhibits premitotic accumulation at centromeres. Consistent with this property, treatment of cells with the topoisomerase-II inhibitor etoposide promotes chromosomal cleavage at sites within centromeric DNA. In the case of the human malaria parasite Plasmodium falciparum, despite a completed genome sequence, there are no experimental data on the nature of centromeres. To address this issue, we have used etoposide-mediated topoisomerase-II cleavage as a biochemical marker to map centromeric DNA on all 14 parasite chromosomes. We find that topoisomerase-II activity is concentrated at single chromosomal loci and that cleavage sites extend over approximately 10 kb. A shared feature of these topoisomerase-II cleavage sites is the presence of an extremely AT-rich ( approximately 97%) domain with a strictly defined size limit of 2.3-2.5 kb. Repetitive arrays identified within the domains do not display interchromosomal conservation in terms of length, copy number, or sequence. These unusual properties suggest that P. falciparum chromosomes contain a class of "regional" centromere distinct from those described in other eukaryotes, including the human host.
authors.affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom. john.kelly@lshtm.ac.uk
authors.forename: John M
authors.initials: JM
authors.lastname: Kelly
authors.forename: Louisa
authors.initials: L
authors.lastname: McRobert
authors.forename: David A
authors.initials: DA
authors.lastname: Baker
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002503:Centromere / Q000201:enzymology / Q000235:genetics; D002875:Chromosomes / Q000201:enzymology / Q000235:genetics; D016384:Consensus Sequence; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D016054:DNA, Protozoan / Q000235:genetics* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D006801:Humans; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D059005:Topoisomerase II Inhibitors
chemical_list: D016054:DNA, Protozoan; D004791:Enzyme Inhibitors; D059005:Topoisomerase II Inhibitors; D005047:Etoposide; D004250:DNA Topoisomerases, Type II