The organization of chromatin has a crutial significance for the control of gene expression (Zhu, Dong et al. 2013) in different biological processes, including genome stability, recombination, developmental reprogramming, and reaction to external stimuli. Changes in histone variants, histone modifications and DNA methylation are usually regarded as epigenetic regulation.
However, these changes may or may not possibly be truly epigenetic in nature considering common epigenetics definition involves mitotic or meiotic heritability (Chinnusamy and Zhu 2009). H2A.Z is a conserved variant of histone H2A that has been involved in many biological processes, such as transcriptional regulation, telomeric silencing, genome stability, cell cycle progression, DNA repair, and recombination (Sura, Kabza et al. 2017). Histone modification and ATP-dependent chromatin remodelling direct chromatin structure to harmonise chromatin packaging and transcriptional access (Qin, Zhao et al.
2014). H2A.Z influences many processes in fungi, plants and animals, including gene expression, recombination, and DNA repair (Xu, Leichty et al. 2018) H2A.Z is greatly enriched at the transcription start site (TSS) of a considerable set of genes across cell types, compatible with a role in the control or regulation of transcription, Genome-wide studies in yeast have revealed that H2A.Z enrichment at promoter-distal nucleosomes is needed for initiation or start of transcription, while being oppositely correlated with transcript levels (Sura, Kabza et al.
2017). Eukaryotic genomes possess several histone variants, and all of them bestow different properties to the nucleosome, which in turn influence many biological processes, most commonly and importantly transcription. Histones may also be altered post translationally and successively affect transcription (Dai, Bai et al. 2017).