Histone H2B (mono methyl K5) is a specific modification of the histone protein H2B at lysine residue 5, where a single methyl group is added. Histone H2B (mono methyl K5) is a core component of the nucleosome, which is essential for the packaging of DNA into chromatin. This modification, along with others, contributes to the regulation of DNA accessibility, thereby influencing transcription regulation, DNA repair, DNA replication, and chromosomal stability. Histone H2B mono methylation, particularly at K5, has been implicated in transcriptional regulation. It is part of a complex set of post-translational modifications known as the "histone code," which affects gene expression.