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1.  The genome of the simian and human malaria parasite Plasmodium knowlesi 
Nature  2008;455(7214):799-803.
Plasmodium knowlesi is an intracellular malaria parasite whose natural vertebrate host is Macaca fascicularis (the ‘kra’ monkey); however, it is now increasingly recognized as a significant cause of human malaria, particularly in southeast Asia1,2. Plasmodium knowlesi was the first malaria parasite species in which antigenic variation was demonstrated3, and it has a close phylogenetic relationship to Plasmodium vivax​4, the second most important species of human malaria parasite (reviewed in ref. 4). Despite their relatedness, there are important phenotypic differences between them, such as host blood cell preference, absence of a dormant liver stage or ‘hypnozoite’ in P. knowlesi, and length of the asexual cycle (reviewed in ref. 4). Here we present an analysis of the P. knowlesi (H strain, Pk1(A+) clone5) nuclear genome sequence. This is the first monkey malaria parasite genome to be described, and it provides an opportunity for comparison with the recently completed P. vivax genome4 and other sequenced Plasmodium genomes6-8. In contrast to other Plasmodium genomes, putative variant antigen families are dispersed throughout the genome and are associated with intrachromosomal telomere repeats. One of these families, the KIRs9, contains sequences that collectively match over one-half of the host CD99 extracellular domain, which may represent an unusual form of molecular mimicry.
PMCID: PMC2656934  PMID: 18843368
2.  Expression of the plasmodial pfmdr1 gene in mammalian cells is associated with increased susceptibility to chloroquine. 
Molecular and Cellular Biology  1994;14(4):2419-2428.
Chloroquine (CQ)-resistant (CQR) Plasmodium falciparum malaria parasites show a strong decrease in CQ accumulation in comparison with chloroquine-sensitive parasites. Controversy exists over the role of the plasmodial pfmdr1 gene in the CQR phenotype. pfmdr1 is a member of the superfamily of ATP-binding cassette transporters. Other members of this family are the mammalian multidrug resistance genes and the CFTR gene. We have expressed the pfmdr1-encoded protein, Pgh1, in CHO cells and Xenopus oocytes. CHO cells expressing the Pgh1 protein demonstrated an increased, verapamil-insensitive susceptibility to CQ. Conversely, no increase in drug susceptibility to primaquine, quinine, adriamycin, or colchicine was observed in Pgh1-expressing cells. CQ uptake experiments revealed an increased, ATP-dependent accumulation of CQ in Pgh1-expressing cells over the level in nonexpressing control cells. The increased CQ accumulation in Pgh1-expressing cells coincided with an enhanced in vivo inhibition of lysosomal alpha-galactosidase by CQ. CHO cells expressing Pgh1 carrying two of the CQR-associated Pgh1 amino acid changes (S1034C and N1042D) did not display an increased CQ sensitivity. Immunofluorescence experiments revealed an intracellular localization of both mutant and wild-type forms of Pgh1. We conclude from our results that wild-type Pgh1 protein can mediate an increased intracellular accumulation of CQ and that this function is impaired in CQR-associated mutant forms of the protein. We speculate that the Pgh1 protein plays an important role in CQ import in CQ-sensitive malaria parasites.
PMCID: PMC358609  PMID: 7511206
3.  Amplification of the multidrug resistance gene pfmdr1 in Plasmodium falciparum has arisen as multiple independent events. 
Molecular and Cellular Biology  1991;11(10):5244-5250.
The multidrug resistance (MDR) phenotype in mammalian tumor cells can involve amplification of mdr genes that results in overexpression of the protein product termed P-glycoprotein. Chloroquine resistance (CQR) in Plasmodium falciparum has similarities with the MDR phenotype in tumor cells, and some isolates of P. falciparum have amplified levels of the pfmdr1 gene. To investigate the nature and origin of pfmdr1 amplicons, we have cloned large regions of a 110-kb amplicon from the CQR cloned isolate B8 by using the yeast artificial chromosome system. We have identified and sequenced the breakpoints of the amplicon by a novel method employing inverted polymerase chain reaction that is applicable to analysis of any large-scale repeat. We show that the five copies of the amplicon in this isolate are in a head to tail configuration. A string of 30 A's flank the breakpoints on each side of the amplified segment, suggesting a mechanism for the origin of the tandem amplification. Polymerase chain reaction analysis with oligonucleotides that cross the B8 breakpoint has shown in 26 independent CQR isolates, 16 of which contain amplified copies of pfmdr1, that amplification of the pfmdr1 gene in P. falciparum has arisen as multiple independent events. These results suggest that this region of the genome is under strong selective pressure.
PMCID: PMC361573  PMID: 1922044
4.  Antifolate drug selection results in duplication and rearrangement of chromosome 7 in Plasmodium chabaudi. 
Molecular and Cellular Biology  1989;9(11):5182-5188.
We selected lines of Plasmodium chabaudi that are resistant to high levels of the antifolate drug pyrimethamine and have shown that rearrangement and duplication of a portion of chromosome 7 has occurred in the resistant lines. This chromosomal duplication results in an increase in the chromosome number from 14 to 15: two derived chromosomes (450 kilobases and 1.1 megabases) were smaller than the original chromosome 7 (1.3 megabases), so that essentially only a 200-kilobase region was duplicated. This region contained the DHFR-TS gene and the closely linked Hsp70 gene. We have macrorestriction mapped chromosome 7 from the pyrimethamine-susceptible line (DS) and also the duplicated chromosome 7s in the resistant line. From these maps, we have proposed a process for the karyotype changes. Sequencing of the DHFR gene from the parent and derived chromosomes showed that there were no mutations in the coding sequence. As a result of the duplication of the DHFR-TS gene, there is at least a twofold increase in expression of the DHFR-TS gene, and this may explain the ability of the pyrimethamine-resistant lines to grow in increased amounts of the drug.
PMCID: PMC363670  PMID: 2601715
5.  Expression of the RESA gene in Plasmodium falciparum isolate FCR3 is prevented by a subtelomeric deletion. 
Molecular and Cellular Biology  1989;9(8):3584-3587.
We show here that the Plasmodium falciparum isolate FCR3 does not express the ring-infected erythrocyte surface antigen (RESA). This is because the 5' end of the RESA gene has been inverted and partly deleted and a telomere has been added to it. We propose a model to explain these events.
PMCID: PMC362412  PMID: 2677678
6.  Changes in repeat number, sequence, and reading frame in S-antigen genes of Plasmodium falciparum. 
Molecular and Cellular Biology  1987;7(8):2968-2973.
The S antigens from different isolates of Plasmodium falciparum exhibit extensive size, charge, and serological diversity. We show here that the S-antigen genes behave as multiple alleles of a single locus. The size heterogeneity results from different numbers, lengths, and/or sequences of tandem repeat units encoded within the S-antigen genes. Two genes studied here encode antigenically different S antigens but nevertheless have closely related tandem repeat sequences. We show that antigenic differences can arise because repeats are translated in different reading frames.
PMCID: PMC367916  PMID: 3313007

Results 1-6 (6)