Core component of nucleosome. Nucleosomes wrap and compact DNA into chromatin, limiting DNA accessibility to the cellular machineries which require DNA as a template. Histones thereby play a central role in transcription regulation, DNA repair, DNA replication and chromosomal stability. DNA accessibility is regulated via a complex set of post-translational modifications of histones, also called histone code, and nucleosome remodeling. The nucleosome is a histone octamer containing two molecules each of H2A, H2B, H3 and H4 assembled in one H3-H4 heterotetramer and two H2A-H2B heterodimers. The octamer wraps approximately 147 bp of DNA. Monoubiquitination of Lys-118 by Bre1 gives a specific tag for epigenetic transcriptional activation and is also prerequisite for histone H3 'Lys-4' and 'Lys-79' methylation. Methylation at Pro-2 increases upon heat shock. GlcNAcylation at Ser-110 promotes monoubiquitination of Lys-118. It fluctuates in response to extracellular glucose, and associates with transcribed genes (Probable). Belongs to the histone H2B family. Was reported to be phosphorylated at Ser-34. However, the paper was retracted because some data, results and conclusions in the paper are not reliable.