**4. Centromeric H3**

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. In *T. gondii*, this histone variant was characterized with the aim to understand the way in which chromosomes are delivered to the daughter cells after mitosis, a process that is still intriguing [21]. In this work, the authors labeled all the histone H3 variants, and used TgCenH3 as a marker of centromeres, to perform ChIP and microarray assays [21]. They found a particular combination of histone PTMs surrounding centromeres; this region had a huge concentration of H3K9 di- and trimethylation, marks usually associated to heterochromatin and found in subtelomeric regions in *P. falciparum* but not in *T. gondii.* In this parasite, these modifications concentrate in two peaks directly flanking the center of the centromere in each chromosome, while H3K4me3 or H3K9ac are not present [21, 52]. In contrast, H3K9me3 and heterochromatin protein 1 (HP1, chromodomain protein that binds to H3K9me3) were not associated with centromeres in *P. falciparum* [23], but rather found in islands of the genome that contain transcriptionally silent members of multigene families [56]. In this parasite, the enrichment of PfCenH3 on centromeres of all the chromosomes has also been demonstrated by genome-wide ChIP-seq analysis [23]. Besides, it has been characterized that a region within the carboxy-terminal histone fold domain, which is also named CENP-A targeting domain (CATD), is essential for mediating centromere targeting, while the N-terminus is not [57].
