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The nucleosome landscape of Plasmodium falciparum reveals chromatin architecture and dynamics of regulatory sequences.

ABSTRACT: In eukaryotes, the chromatin architecture has a pivotal role in regulating all DNA-associated processes and it is central to the control of gene expression. For Plasmodium falciparum, a causative agent of human malaria, the nucleosome positioning profile of regulatory regions deserves particular attention because of their extreme AT-content. With the aid of a highly controlled MNase-seq procedure we reveal how positioning of nucleosomes provides a structural and regulatory framework to the transcriptional unit by demarcating landmark sites (transcription/translation start and end sites). In addition, our analysis provides strong indications for the function of positioned nucleosomes in splice site recognition. Transcription start sites (TSSs) are bordered by a small nucleosome-depleted region, but lack the stereotypic downstream nucleosome arrays, highlighting a key difference in chromatin organization compared to model organisms. Furthermore, we observe transcription-coupled eviction of nucleosomes on strong TSSs during intraerythrocytic development and demonstrate that nucleosome positioning and dynamics can be predictive for the functionality of regulatory DNA elements. Collectively, the strong nucleosome positioning over splice sites and surrounding putative transcription factor binding sites highlights the regulatory capacity of the nucleosome landscape in this deadly human pathogen.

SUBMITTER: Kensche PR

PROVIDER: S-EPMC4797266 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature

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The nucleosome landscape of Plasmodium falciparum reveals chromatin architecture and dynamics of regulatory sequences.

Kensche Philip Reiner PR Hoeijmakers Wieteke Anna Maria WA Toenhake Christa Geeke CG Bras Maaike M Chappell Lia L Berriman Matthew M Bártfai Richárd R

Nucleic acids research 20151117 5

In eukaryotes, the chromatin architecture has a pivotal role in regulating all DNA-associated processes and it is central to the control of gene expression. For Plasmodium falciparum, a causative agent of human malaria, the nucleosome positioning profile of regulatory regions deserves particular attention because of their extreme AT-content. With the aid of a highly controlled MNase-seq procedure we reveal how positioning of nucleosomes provides a structural and regulatory framework to the trans ...[more]

PMID: 26578577

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Project description:In eukaryotes, the chromatin architecture has a pivotal role in regulating all DNA-related processes. For P. falciparum, the causative agent of human malaria, the nucleosome landscape of the extremely AT-rich intergenic regulatory regions is largely unexplored. With the aid of a highly controlled MNase-seq procedure we reveal how positioning of nucleosomes provides a structural and regulatory framework to the transcriptional unit. We observe strong positioning of nucleosomes around splice sites that could aid co-transcriptional splicing events. In addition, nucleosome depleted regions are apparent hallmarks of transcription start sites (TSSs) and may support pre-initiation complex assembly. Moreover, we reveal nucleosome occupancy dynamics on strong TSSs during intraerythrocytic development, which correlate with gene expression changes and we observe a characteristic nucleosome architecture of functional - but not inert - TGCATGCA DNA motifs. Collectively, these findings highlight the regulatory capacity of the nucleosome landscape of this deadly human pathogen. Mnase-seq during the intra-erythrocytic asexual cycle of Plasmodium falciparum var2csa-panned 3D7 parasites for 8 time-points, every 5 hours starting from 5 hours post invasion until 40 hours post-invasion (T5-T40). Cycle length of these parasites is ~43 hours, synchronicity window is ~ 8 hours. T40 has 2 technical replicates (independent digestions; T40A, T40B). Additionally, pellet control sample (T15), histone H4-ChIP control (T40A) and sonicated and amplified genomic DNA. Chromatin was digested using a combined MNase + exonuclease III treatment. Libraries were prepared according to a Plasmodium-optimized library preparation procedure including KAPA polymerase-mediated PCR amplification. Strand-specific RNA-seq for expression quantification during the intra-erythrocytic asexual cycle of Plasmodium falciparum var2csa-panned 3D7 parasites for 8 time-points every 5 hours starting from 5 hours post invasion invasion until 40 hours post-invasion (T5-T40). Cycle length of these parasites is ~43 hours, synchronicity window is ~ 8 hours. These samples are originating from the exact same batch of parasites as are the MNase-Seq libraries. Libraries were prepared according to a Plasmodium-optimized library preparation procedure including KAPA polymerase-mediated PCR amplification.

Project description:Epigenetic modifications of histones and regulation of chromatin structure have been implicated in regulation of virulence gene families in P. falciparum. To better understand chromatin-mediated gene regulation, we used a high-density oligonucleotide microarray to map the position and enrichment of nucleosomes across the entire genome of P. falciparum at three time points of the intra-erythrocytic developmental cycle (IDC) in vitro. We used an unmodified histone H4 antibody for chromatin immunoprecipitation of nucleosome-bound DNA.We observed generally low nucleosomal occupancy of intergenic regions and higher occupancy of protein coding regions. In contract to the overall small fluctuation of nucleosomal occupancy in most coding regions throughout the IDC, subtelomeric genes encoding surface proteins such as var and rif, as well as some core chromosomal genes such as transcription factors, showed large changes in chromatin structure. Telomeres harbored a region with the highest nucleosomal occupancy of the genome and also exhibited large changes with higher nucleosomal occupancy at schizont stages. While many of these subtelomeric genes were previously shown to be modified by H3K9 trimethylation, we also identified some housekeeping genes in core chromosome regions that showed extensive changes in chromatin structure but do not contain this modification. tRNA and basal transcription factor genes showed low nucleosomal occupancy at all times, suggesting of an open chromatin structure that might be permissive for constitutively high levels of expression. Generally, nucleosomal occupancy was not correlated with the steady-state mRNA levels. Several var genes were exceptions: the var gene with the highest expression level showed the lowest nucleosomal occupancy, and selection of parasites for var2CSA expression resulted in lower nucleosomal occupancy at the var2CSA locus. We identified nucleosome-free regions in intergenic regions that may serve as transcription start sites or transcription factor binding sites. Using the nucleosomal occupancy data as the baseline, we further mapped the genome-wide enrichment of H3K9 acetylation and detected general enrichment of this mark in intergenic regions.These data on nucleosome enrichment changes add to our understanding of the influence of chromatin structure on the regulation of gene expression. Histones are generally enriched in coding regions, and relatively poor in intergenic regions. Histone enrichment patterns allow for identification of new putative gene-coding regions. Most genes do not show correlation between chromatin structure and steady-state mRNA levels, indicating the dominant roles of other regulatory mechanisms. We present a genome-wide nucleosomal occupancy map, which can be used as a reference for future experiments of histone modification mapping.

Dataset Information

The nucleosome landscape of Plasmodium falciparum reveals chromatin architecture and dynamics of regulatory sequences.

Publications

The nucleosome landscape of Plasmodium falciparum reveals chromatin architecture and dynamics of regulatory sequences.

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