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 (By similarity). Associated with pericentromeric heterochromatin. Levels relative to total cellular protein, increase as differentiation proceeds towards the final culminant. The levels of tri-methylation of Lys-5 (H3K4me3) diminish considerably during the process of differentiation. In contrast, the level of mono-methylation of Lys-5 (H3K4me1) becomes significantly enhanced during differentiation. There is a slight dip in di-methylation of Lys-5 (H3K4me2) around the time of aggregation and the level of this mark again dips during the final stages of spore formation. The levels of H3K4me1 and H3K4me2 rise during the inactivation of rasG that occurs after the onset of differentiation. The level of dimethylation at this locus peaks coinciding with the loss of H3K4me3. This enrichment of dimethyl H3K4 declines as the rise in the level of H3K4me1 continues. H3K79me2 (di-methylation of Lys-80) is expressed during the whole life cycle. Acetylation is generally linked to gene activation. Different methylation states of H3K4 mark distinct developmental phases. H3K4me2 is associated with euchromatic regions. H3K4me3 is a mark of active chromatin. set1 is responsible for all mono-, di- and tri-methylation of H3K4. H3K4me facilitates subsequent acetylation of H3 and H4. Methylation at H3K9 is linked to gene repression (By similarity). H3S10ph, which is linked to gene activation, prevents methylation at H3K9 but facilitates acetylation of H3 and H4. Belongs to the histone H3 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: H3K4me1/2/3 = mono-, di- and trimethylated Lys-5; H3K9ac = acetylated Lys-10; H3K9me1 = monomethylated Lys-10; H3S10ph = phosphorylated Ser-11; H3K14ac = acetylated Lys-15; H3K14me2 = dimethylated Lys-15; H3K18ac = acetylated Lys-19; H3K18me1 = monomethylated Lys-19; H3K23ac = acetylated Lys-24; H3K23me1 = monomethylated Lys-24; H3K27ac = acetylated Lys-28; H3K27me1/2/3 = mono-, di- and trimethylated Lys-28; H3K36ac = acetylated Lys-37; H3K36me1/2/3 = mono-, di- and trimethylated Lys-37; H3K56ac = acetylated Lys-57; H3K64ac = acetylated Lys-68; H3K79me1/2/3 = mono-, di- and trimethylated Lys-80.