Replication of the Plasmodium falciparum apicoplast DNA initiates within the inverted repeat region

The 35 kb apicoplast genomes (pIDNA) of Plasmodium,falciparum and Toxoplasma gondii share close sequence similarity but differ in their in vivo topologies. Although sequence analysis of tandem repeats of T gondii pIDNA has suggested the presence of replication initiation sites within the inverted repeat region, the replication origins (ori) of the P.falciparum circular pIDNA have not been identified. Using 5' end-labelled nascent DNA as probe, we demonstrate that the ori of P.falciparum pIDNA is localised within the inverted repeat region. Our results also indicate the presence of two initiation sites within each inverted repeat segment of the circular pIDNA of P fialcipartim suggestive of a four D-loop/bi-directional ori mechanism of DNA replication. (C) 2002 Elsevier Science B.V. All rights reserved.