A genetic screen for improved plasmid segregation reveals a role for Rep20 in the interaction of Plasmodium falciparum chromosomes.
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.
O'Donnell
Rebecca A
RA
The Walter & Eliza Hall Institute of Medical Research, Victoria 3050, Australia.
Freitas-Junior
Lúcio H
LH
Preiser
Peter R
PR
Williamson
Donald H
DH
Duraisingh
Manoj
M
McElwain
Terry F
TF
Scherf
Artur
A
Cowman
Alan F
AF
Crabb
Brendan S
BS
D000818:Animals; D020090:Chromosome Segregation / Q000235:genetics / Q000502:physiology*; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D016054:DNA, Protozoan / Q000235:genetics / Q000502:physiology*; D004274:DNA, Recombinant / Q000235:genetics / Q000378:metabolism; D005111:Extrachromosomal Inheritance / Q000235:genetics / Q000502:physiology*; D015723:Gene Library; D005822:Genetic Vectors / Q000235:genetics*; D008938:Mitosis; D010957:Plasmids / Q000235:genetics*; D010963:Plasmodium falciparum / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid; D016615:Telomere / Q000378:metabolism; D014162:Transfection
D004269:DNA, Bacterial; D016054:DNA, Protozoan; D004274:DNA, Recombinant