Canonical and variant histones of protozoan parasites

Abstract

Protozoan parasites have tremendously diverse lifestyles that require adaptation to a remarkable assortment of different environmental conditions. In order to complete their life cycles, protozoan parasites rely on fine-tuning gene expression. In general, protozoa use novel regulatory elements, transcription factors, and epigenetic mechanisms to regulate their transcriptomes. One of the most surprising findings includes the nature of their histones--these primitive eukaryotes lack some histones yet harbor novel histone variants of unknown function. In this review, we describe the histone components of different protozoan parasites based on literature and database searching. We summarize the key discoveries regarding histones and histone variants and their impact on chromatin regulation in protozoan parasites. In addition, we list histone genes IDs, sequences, and genomic localization of several protozoan parasites and Microsporidia histones, obtained from a thorough search of genome databases. We then compare these findings with those observed in higher eukaryotes, allowing us to highlight some novel aspects of epigenetic regulation in protists and to propose questions to be addressed in the upcoming years.

Apicomplexa and Histone Variants: What’s New?

“…CenH3, the centromere-specific H3, has been observed in animals, fungi, and plants [24] and also in Apicomplexa, including T. gondii, Plasmodium spp., and N. caninum [55]. This fact was recently confirmed by Fraschka et al [42] who found the centromeres depleted of PfH3.3 and PfH3, but occupied by PfCenH3.…”

H2A.Z and H2B.Z double‐variant nucleosomes define intergenic regions and dynamically occupy var gene promoters in the malaria parasite Plasmodium falciparum

“…Protist parasites of the trypanosomatids and apicomplexa are unique in possessing lineage‐specific variants of H2B. Originally both lineages were called H2Bv (Dalmasso et al ., ) but the apicomplexan variants were recently reclassified as H2B.Z to reflect their independent evolution (Talbert et al ., ). Both Trypanosoma brucei H2Bv and Toxoplasma gondii H2B.Z have been shown to exclusively dimerize with the alternative histone H2A.Z (Dalmasso et al ., ; Siegel et al ., ).…”

“…Protist parasites of the trypanosomatids and apicomplexa are unique in possessing lineage-specific variants of H2B. Originally both lineages were called H2Bv (Dalmasso et al, 2011) but the apicomplexan variants were recently reclassified as H2B.Z to reflect their independent evolution (Talbert et al, Accepted 9 January, 2013. For correspondence.…”

Toxoplasma gondiiHsp90: potential roles in essential cellular processes of the parasite

“…Although the Hsp90 PPI network presents some components of chromatin and transcriptional machinery as putative TgHsp90 interactors (Table S1), there is an important gap in this field since only a basal transcriptional machinery has been detected in apicomplexan parasites (Meissner and Soldati, 2005). In addition, the involvement of an epigenetic mechanism in T. gondii gene regulation has been recently documented (Dalmasso et al 2011; Croken et al 2012). On the other hand, the role of Hsp90 in transcriptional activities, chromatin modulation, RNA processing/splicing proteins and DNA replication/damage-response has been recently reviewed (Sawarkar et al 2012).…”