Abstract
The regulation of variant gene expression in Plasmodium falciparum is still only partially understood. Regulation of var genes, the most studied gene family involved in antigenic variation, is orchestrated by a dynamic pattern of inherited chromatin states. Although recent evidence pointed to epigenetic regulation of transcribed and repressed rif loci, little is known about specific on/off associated histone modifications of individual rif genes. To investigate the chromatin marks for transcribed and repressed rif loci, we cultivated parasites and evaluated the transcriptional status of chosen rif targets by qRT-PCR and performed ChIP assays using H3K9ac and H3K9me3 antibodies. We then monitored changes in the epigenetic patterns in parasites after several reinvasions and also evaluated the “poised” mark in trophozoites and schizonts of the same erythrocytic cycle by ChIP using H3K4me2 specific antibodies. Our results show that H3K9 is acetylated in transcribed rif loci and trimethylated or even unmodified in repressed rif loci. These transcriptional and epigenetic states are inherited after several reinvasions. The poised modification H3K4me2 showed a tendency to be more present in loci in trophozoites that upon progression to schizonts strongly transcribe the respective locus. However, this effect was not consistently observed for all monitored loci. While our data show important similarities to var transcription-associated chromatin modifications, the observed swiftly occurring modifications at rif loci and the absence of H3K9 modification point to a different dynamic of recruitment of chromatin modifying enzymes.
Highlights
The human malaria parasite Plasmodium falciparum maintains its persistence in the vertebrate host at least in part by expression of several variant proteins at the surface of infected erythrocytes
In order to establish if the dynamics of activation and repression of rif loci are associated with the same epigenetic landmarks as var loci, we first performed a qRT-PCR-based rif transcript analysis in parasites previously selected for cytoadherence in CHO-CD36, since in this phenotype a number of rif loci were found active with rapid switching after a small number of reinvasions and given the large number of rif genes the analysis was restricted to these loci [5]
In order to evaluate the epigenetic state and the posttranslational modifications of the chromatin associated to the monitored rif loci, Chromatin Immunoprecipitation (ChIP) was performed using H3K9me3 and H3K9ac-specific antibodies
Summary
The human malaria parasite Plasmodium falciparum maintains its persistence in the vertebrate host at least in part by expression of several variant proteins at the surface of infected erythrocytes. The most important variant antigen is PfEMP-1 (Plasmodium falciparum erythrocyte membrane protein 1) which is encoded by approximately 60 members of the var multigene family [1] The transcription of this gene family is strictly controlled by a complex mechanism termed allelic exclusion and it is assumed that one or very few var genes are expressed per single parasite [2]. Proteins of RIFIN, STEVOR and PFM2tm families are expressed at the infected red blood cell surface and little is known about the function of these antigens regarding malaria persistence, pathogeny and cytoadherence
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
