DNA base excision repair in human malaria parasites is predominantly by a long-patch pathway

Mammalian cells repair apurinic/apyrimidinic (AP) sites in DNA by two disti nct pathways: a polymerase beta (pol beta)-dependent, short- (one nucleotid e) patch base excision repair (BER) pathway, which is the major route, and a PCNA-dependent, long- (several nucleotide) patch BER pathway. The ability of a cell-free lysate prepared from asexual Plasmodium falciparum malaria parasites to remove uracil and repair AP sites in a variety of DNA substrat es was investigated. We found that the lysate contained uracil DNA glycosyl ase, AP endonuclease, DNA polymerase, flap endonuclease, and DNA ligase act ivities. This cell-free lysate effectively repaired a regular or synthetic AP site on a covalently closed circular (ccc) duplex plasmid molecule or a long (382 bp), Linear duplex DNA fragment, or a regular or reduced AP site in short (28 bp), duplex oligonucleotides. Repair of the AP sites in the va rious DNA substrates involved a long-patch BER pathway. This biology is dif ferent from mammalian cells, yeast, Xenopus, and Escherichia coli, which pr edominantly repair AP sites by a one-nucleotide patch BER pathway. The appa rent absence of a short-patch BER pathway in P. falciparum may provide oppo rtunities to develop antimalarial chemotherapeutic strategies for selective ly damaging the parasites in vivo and will allow the characterization of th e long-patch BER pathway without having to knock-out or inactivate a short- patch BER pathway, which is necessary in mammalian cells.