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  • The EMBO Journal (2002) 21, 1231 - 1239
  • doi:10.1093/emboj/21.5.1231

A genetic screen for improved plasmid segregation reveals a role for Rep20 in the interaction of Plasmodium falciparum chromosomes

Rebecca A. O'Donnell1,2, Lúcio H. Freitas-Junior3, Peter R. Preiser4, Donald H. Williamson4, Manoj Duraisingh1, Terry F. McElwain1,2,5, Artur Scherf3, Alan F. Cowman1 and Brendan S. Crabb1

  1. The Walter & Eliza Hall Institute of Medical Research, Victoria 3050, Australia
  2. Department of Microbiology & Immunology and the Cooperative Research Centre for Vaccine Technology, The University of Melbourne, Victoria 3010, Australia
  3. Unité de Biologie des Interactions Hôte-Parasite, CNRS URA 1960, Institut Pasteur, F-75724 Paris Cedex 15, France
  4. National Institute of Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
  5. Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040, USA

Correspondence to:

Brendan S. Crabb, E-mail: crabb@wehi.edu.au

Received 26 November 2001; Accepted 11 January 2002; Revised 11 January 2002

Bacterial plasmids introduced into the human malaria parasite Plasmodium falciparum replicate well but are poorly segregated during mitosis. In this paper, we screened a random P.falciparum genomic library in order to identify sequences that overcome this segregation defect. Using this approach, we selected for parasites that harbor a unique 21 bp repeat sequence known as Rep20. Rep20 is one of six different repeats found in the subtelomeric regions of all P.falciparum chromosomes but which is not found in other eukaryotes or in other plasmodia. Using a number of approaches, we demonstrate that Rep20 sequences lead to dramatically improved episomal maintenance by promoting plasmid segregation between daughter merozoites. We show that Rep20+, but not Rep20-, plasmids co-localize with terminal chromosomal clusters, indicating that Rep20 mediates plasmid tethering to chromosomes, a mechanism that explains the improved segregation phenotype. This study implicates a direct role for Rep20 in the physical association of chromosome ends, which is a process that facilitates the generation of diversity in the terminally located P.falciparum virulence genes.

  • Keywords:

    • plasmid segregation,
    • Plasmodium falciparum,
    • Rep20,
    • terminal chromosomal cluster,
    • transfection