Gene expression/regulation nucleosomes

Histones are basic proteins that are made up by a globular domain and an N-terminal tail that protrudes from the nucleosome. Nucleosomes form the basic unit of chromatin and are made up by a complex of DNA wrapped around an octamer of histones formed by pairs of the histones H2A, H2B, H3, and H4 (45,46) (Fig. 1). Post-translational modification of the core histone tails by methylation, acetylation, phosphorylation, ubiquitina-tion, or sumoylation can alter the structure of the nucleosomes and thus alter gene expression. These post-translational modifications determine the structure and pattern of chromatin condensation and determine the histone code that drives gene transcriptional regulation (47,48). Below are briefly described the factors determining the histone acetylation and methylation. 

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