Analysis der P. falciparum var Gene: genomische Verteilung, Regulation der Genexpression, und Bindungseigenschaften in natürlich infizierten menschlichen Blutproben

• Forschungsstelle: TPH
• Projektnummer: 1.01
• Projekttitel Englisch: Analysis of P. falciparum var genes: genomic distribution, regulation of gene-expression and binding properties in naturally infected human blood samples.

Schlüsselwörter (Englisch)

Malaria, Plasmodium falciparum, gene regulation, PfEMP1, antigenic variation, var genes, transfection, antisense RNA, sequence analysis, trafficking

Kurzbeschreibung (Englisch)

The project focuses on antigenic variation in the malaria parasite Plasmo-dium falciparum in order to understand this major process in the pathogenicity of malaria.

Projektziele (Englisch)

To confirm the hypothesis that the dimorphism of the var upstream region has a biological significance for var gene regulation and participates in the cooperative silencing with the var intron.To test the hypothesis that var antisense RNA is present and plays a role in silencing of var genes. To test the hypothesis that var gene expression in naturally occurring infections differs significantly between severe and non severe infections. To analyse PfEMP1 interaction partners responsible for transport of PfEMP1 through the erythrocyte cytosol.

Abstract (Englisch)

Cytoadherence of Plasmodium falciparum is a major contributor to the pathology of malaria. Adherence to endothelial receptors is mediated by parasite derived proteins termed PfEMP1. PfEMP1 shows antigenic variation and is encoded by the var gene family comprising 50 to 60 genes per haploid genome. We have shown that var upstream regions are dimorphic and conserved and that this dimorphism coincides with the chromosomal location of var genes. We showed that the upstream regions function as promoters driving transcription in transient transfections of P. falciparum. We identified various sequences which bind different DNA binding proteins, indicating different regulation processes for both types of var genes, and we observed binding of proteins at the time when var genes are not transcribed, suggesting a repressor role for these proteins. In this ongoing project we try to elucidate the molecular mechanisms of the respective gene regulation, but also try to elucidate the fate of the molecule from the intracellular parasite to the incorporation into the host cell membrane. We are furthermore interested to compare laboratory findings with findings in naturally infected blood samples.

Publikationen / Ergebnisse (Englisch)

Beck, H.P., Felger, I., Huber, W., Steiger, S., Smith, T., Weiss, N., Alonso, P., Tanner, M. 1997 Analysis of multiple Plasmodium falciparum infections in Tanzanian children during the phase III trial of the malaria vaccine SPf66. J. Inf.ect. Dis. 175,: 921-926.

Degen, R., Weiss, N., Beck, H.-P. 2000 Plasmodium falciparum: cloned and expressed CIDR domains of PfEMP1 bind to Chondroitin-Sulfate A (CSA). Exp. Parasitol. 95: 113-121.

Kaestli, M., Cortés, A., Lagog, M., Ott, M., Beck, H.-P. Longitudinal assessment of Plasmodium falciparum var gene transcription in naturally infected asymptomatic children in Papua New Guinea. J. Inf. Dis. (submitted)

Schneider, A.G., Felger, I., Smith, T., Abdullah, S., Beck, H.P., Mshinda, H. 2001 A point mutation in codon 76 of pfcrt of Plasmodium falciparum is positively selected for by chloroquine treatment in Tanzania. Infection, Genetics, and Evolution 18, 1-7.

Spielmann, T., Beck, H.-P. 2000 Analysis of stage-specific transcription in Plasmodium falciparum reveals a set of genes exclusively transcribed in ring stage parasites. Mol. Biochem. Parasitol. 111, 453-458.

Spielmann, T., Fergusen, D.J.P., Beck, H.- P. 2003 etramps, a new Plasmodium falciparum gene family coding for developmentally regulated and highly charged membrane proteins located at the parasite-host cell. Mol. Biol. Cell 14, 4; 1529-1544.

Spycher, C., Kump, E., Steiger, S., Klonis, N., Spielmann, T., Tilley, L., Beck, H.-P. 2003 MAHRP-1, a novel Plasmodium falciparum histidine-rich protein, binds ferriprotopophyrin IX and localises to the Maurer=s clefts. J. Biol. Chem. 278, 35373-83.

Voss, T.S., Thompson, K., Waterkeyn, J., Felger, I., Weiss, N., Cowman, A.F., Beck. H.-P. 2000 Genomic distribution and functional characterisation of two distinct and conserved Plasmodium falciparum var gene 5' flanking sequences. Mol. Biochem. Parasitol. 107: 103-15.

Voss TS, Kaestli M, Vogel D, Bopp S, Beck HP. 2003 Identification of nuclear proteins that interact differentially with Plasmodium falciparum var gene promoters. Mol Microbiol. 48: 1593-607.

Voss, T.S., Mini, T., Jenoe, P., Beck, H.- P. 2002 Plasmodium falciparum Possesses a Cell Cycle-regulated Short Type Replication Protein A Large Subunit Encoded by an Unusual Transcript. J. Biol. Chem. 17,17493-17501.