Histone acetylation is a hallmark of chromatin that has an open structure that can be accessed by DNA and RNA polymerases as well as transcription factors, resulting in the activation of gene transcription (Filippakopoulos and Knapp, 2014). Correspondingly, histone methylation increases the basicity and hydrophobicity of histone tails and the affinity of certain proteins, such as transcription factors, toward DNA (Teperino et al., 2010), thus affecting the gene expression.