Histones are proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes. Nucleosomes are composed of four core histone proteins (H2A, H2B, H3 and H4). Histones are dynamic proteins, undergoing multiple types of post-translational modifications. Histone methylation is a major determinant for the formation of active and inactive regions of the genome and is crucial for the proper programming of the genome during development. Trimethylation of H3K27 (H3K27me3) is a transcriptionally repressive post-translational modification and has been implicated in a number of cancers, including diffuse large B cell lymphoma (DLBCL).