Unknown,Transcriptomics,Genomics,Proteomics

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Heterochromatin protein 1 secures survival and transmission of malaria parasites

ABSTRACT: The malaria parasite Plasmodium falciparum relies on clonally variant gene expression in order to escape immune recognition and secure continuous proliferation during blood stage infection. Here, we studied the role of heterochromatin protein 1 (HP1), an evolutionary conserved regulator of heritable gene silencing, in the biology of P. falciparum blood stage parasites. We demonstrate that conditional PfHP1 depletion de-represses hundreds of heterochromatic virulence genes and disrupts the elusive mechanism underlying mutually exclusive expression and antigenic variation of PfEMP1. Intriguingly, we also discovered that the PfHP1-dependent regulation of an ApiAP2 transcription factor controls the switch from asexual parasite proliferation to sexual differentiation. This uncovers the first mechanistic insight into the unknown pathway triggering gametocyte conversion and establishes a new concept of HP1-dependent cell fate decision in unicellular eukaryotes. P. falciparum 3D7 parasites expressing endogenous PfHP1-GFP-DD were grown in presence of 4nM WR/625nM Shield-1 (3D7/HP1ON) or 4nM WR (3D7/HP1OFF). RNA extracted from these samples at eleven consecutive time points each was processed for microarray analysis.

ORGANISM(S): Plasmodium falciparum 3D7

SUBMITTER: Till Voss

PROVIDER: E-GEOD-53176 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Background: Malaria is a one of the most important infectious diseases and is caused by parasitic protozoa of the genus Plasmodium. Previously, the quantitative characterization of the P. falciparum transcriptome demonstrated that the strictly controlled progression of these parasites through their intra-erythrocytic developmental cycle is accompanied by a continuous cascade of gene expression. Although such analyses have proven immensely useful, the precise correlations between transcript and protein abundance remain under-scrutinized. Results: Here, we present a quantitative time-course analysis of relative protein abundance for schizont-stage parasites (34-46 hours post-invasion) based on 2D-gel electrophoresis of protein samples labeled with DIGE fluorescent dyes. For this purpose we analyzed parasite samples taken at four-hour intervals from a tightly synchronized culture and established more than 500 individual protein abundance profiles with high temporal resolution and quantitative reproducibility. Approximately half of all profiles exhibit a significant change in abundance and 12% display an expression peak during the observed 12-hour time interval. Intriguingly, identification of 54 protein spots by mass spectrometry revealed that 58% of the corresponding proteins including actin-I, enolase, eIF4A, eIF5A, and several heat shock proteins are represented by more than one isoform, presumably due to post-translational modifications, with the various isoforms of a given protein frequently showing different expression patterns. Furthermore, comparisons with transcriptome data generated from the same parasite samples reveal significant post-transcriptional gene expression regulation. Conclusions: Together, our data indicate that both post-transcriptional and post-translational events are widespread and of presumably great biological significance during the intra-erythrocytic development of P. falciparum. Additional comment: In essence, the microarray data generated in this study is a repeat of the transcriptome analysis described in Bozdech et al., PLoS Biol 2003, 1(1):E5. Differences include (1) an improved set of oligonucleotides [see Hu et al., BMC Bioinformatics 2007, 8:350] used in the study associated with this GEO entry, and (2) the sampling at only four timepoints during the intra-erythrocytic development cycle (schizont stage) to match and complement the samples processed in the concomitant proteomics analysis. Four timepoint samples were harvested from a tightly synchronized 6 liter biofermenter culture of P. falciparum during schizont stage (at 34, 38, 42, and 46 hours post-invasion) and compared against a 3D7 RNA reference pool.

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Heterochromatin protein 1 secures survival and transmission of malaria parasites

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