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Transcription and coregulation of multigene families in Plasmodium falciparum

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Subtelomeric regions in the Plasmodium genome are enriched with members of three major multigene families: var, rif and stevor. In this article, we discuss a recent study by Sharp and colleagues that focused on the transcribed repertoire of var and stevor genes in asexual and sexual Plasmodium parasites. Transcription of these two multigene families seems to be unlinked in asexual parasites. Parasites in the gametocyte stages transcribe members of the upsC subset of var genes, which indicates the intriguing possibility of their involvement in gametocyte adhesion.

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The subtelomeric gene families of Plasmodium falciparum

Telomeres are sites of specialized expression, recombination and localization within the nucleus. Pathogens such as Candida glabrata, Pneumocystis carinii and Trypanosoma brucei exploit the properties of telomeres by having genes that are important for pathogenesis and immune evasion encoded within subtelomeric regions 1, 2, 3. The subtelomeric regions of P. falciparum are enriched with members from three major multigene families that encode variant proteins: var, which encodes P. falciparum

Is transcription of var and stevor coregulated?

P. falciparum coregulates expression of some genes that share physical proximity within the chromosomes based on their stage-specific expression [10] and/or their functional relationship [11]. Therefore, it is possible that members of the different P. falciparum multigene families that are located within the subtelomeric regions are coregulated. Transcription of a single, dominant var gene peaks early in the intra-erythrocytic life cycle of the parasite 12, 13 and is followed later [7] by

var and stevor transcription in gametocytes

P. falciparum gametocytes take up to ten days to reach maturity. It is unknown how the parasite evades the human immune system during this time and what ligands mediate the adhesion of gametocyte-containing IEs to various host receptors. STEVOR, PfEMP1 and RIFIN are all candidates that are present in gametocytes [11] but only STEVOR has been shown to be associated with the gametocyte-containing IE membrane, although it is not known whether they are exposed on the IE surface [8]. Sharp et al.

Antigenic constraints

The observation by Sharp et al. that transcripts from a restricted repertoire of stevor genes dominate in parasites in IEs indicates a var gene-like model in which restricted expression of stevor protects the majority of the stevor repertoire from exposure to the immune system. A strategy of preserving the antigenic repertoire is also consistent with the findings of Sharp et al. that var and stevor transcription is not coregulated. Coregulation that leads to linked expression of variant surface

Acknowledgements

We thank Stuart Ralph and Stephen Rogerson for their advice on this manuscript

References (28)

  • M. Kaviratne

    Small variant STEVOR antigen is uniquely located within Maurer's clefts in Plasmodium falciparum-infected red blood cells

    Eukaryot. Cell

    (2002)
  • L. McRobert

    Distinct trafficking and localization of STEVOR proteins in three stages of the Plasmodium falciparum life cycle

    Infect. Immun.

    (2004)
  • S. Sharp

    Programmed transcription of the var gene family, but not of stevor, in Plasmodium falciparum gametocytes

    Eukaryot. Cell

    (2006)
  • Z. Bozdech

    The transcriptome of the intraerythrocytic developmental cycle of Plasmodium falciparum

    PLoS Biol.

    (2003)
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