Evidence on the chromosomal location of centromeric DNA in Plasmodium falciparum from etoposide-mediated topoisomerase-II cleavage

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 parasitePlasmodium 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 ≈10 kb. A shared feature of these topoisomerase-II cleavage sites is the presence of an extremely AT-rich (≈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 thatP. falciparum chromosomes contain a class of “regional” centromere distinct from those described in other eukaryotes, including the human host.