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. Monoubiquitinated by the ubc2-bre1 complex to form H2BK123ub1. H2BK123ub1 gives a specific tag for epigenetic transcriptional activation and is also prerequisite for H3K4me and H3K79me formation. H2BK123ub1 also modulates the formation of double-strand breaks during meiosis and is a prerequisite for DNA-damage checkpoint activation (By similarity). Acetylated by gcn5 to form H2BK11ac and H2BK16ac. H2BK16ac can also be formed by esa1. Acetylation of N-terminal lysines and particularly formation of H2BK11acK16ac has a positive effect on transcription (By similarity). Sumoylation to form H2BK6su or H2BK7su, and probably also H2BK16su or H2BK17su, occurs preferentially near the telomeres and represses gene transcription. Belongs to the histone H2B family. To ensure consistency between histone entries, we follow the 'Brno' nomenclature for histone modifications, with positions referring to those used in the literature for the 'closest' model organism. Due to slight variations in histone sequences between organisms and to the presence of initiator methionine in UniProtKB/Swiss-Prot sequences, the actual positions of modified amino acids in the sequence generally differ. In this entry the following conventions are used: H2BK6ac = acetylated Lys-8; H2BK6su = sumoylated Lys-8; H2BK7ac = acetylated Lys-9; H2BK7su = sumoylated Lys-9; H2BK11ac = acetylated Lys-15; H2BK16ac = acetylated Lys-26; H2BK16su = sumoylated Lys-26; H2BK17su = sumoylated Lys-27; H2BK123ub1 = monoubiquitinated Lys-135.