Variant histone H3 which replaces conventional H3 in a wide range of nucleosomes in active genes. Constitutes the predominant form of histone H3 in non-dividing cells and is incorporated into chromatin independently of DNA synthesis. Deposited at sites of nucleosomal displacement throughout transcribed genes, suggesting that it represents an epigenetic imprint of transcriptionally active chromatin. 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. The H3K9meK27me dimethylated N-terminal tail of histone H3 can directly interact with the chromodomains of CMT3 and/or LHP1. Interacts with AHL27. Binds to HIRA (PubMed:25086063). Localized at rDNA loci in the nucleolus. A number of isoforms are produced. According to EST sequences. Ubiquitous. Expressed in a replication-independent manner. Strong expression in the generative cell of early bicellular pollen, but not detected in late bicellular and tricellular pollen. Can be acetylated to form H3K9ac, H3K14ac, H3K18ac and H3K23ac. H3K9ac could compete with H3K9me and prevent gene silencing. H3K9acK14ac molecules are 30-fold less abundant than H3K9ac or H3K14ac. Very low level of H3K9meK14ac. H3K14 is specifically acetylated by HAG1 and deacetylated by HDA6. H3K9ac is deacetylated by HDT1. H3K9ac is restricted to euchromatin. H3K18ac, but not H3K9ac, is cell-cycle dependent and linked to replication. Reduced H4R3me2s increases H3K14ac in the FLC chromatin and activates or maintains its transcription. Vernalization decreases H3K9/14ac in the promoter region of FLC. Mono-, di- or trimethylated to form mainly H3K4me1/2/3, H3K9me1/2/3 and H3K36me1/2/3. Very low monomethylation at H3K18me1 or H3K23me1. H3K4me1/2/3, H3K9me3, H3K27me3 and H3K36me1/2/3 are typical marks for euchromatin, whereas heterochromatic chromocenters are enriched in H3K9me1/2 and H3K27me1/2. H3K27me3 is largely restricted to the transcribed regions of single genes and not associated with low-nucleosome density regions. SUVR1 to SUVR5, ASHH1 to ASHH3 and ASHR1 to ASHR3 methylate H3, with ASHH2 methylating specifically H3K4 and H3K36. Monomethylation at H3K27me1 by ATXR5/6 is inhibited by the presence of Thr-32. The Su(var)3-9 homolog proteins (SUVH1 to SUVH10) are H3K9-specific methyltransferases. Among them, KRYPTONITE (SUVH4) is only involved in di- or trimethylation. Regarding H3K9, the major forms are H3K9me1 (20%) and H3K9me2 (10%), while H3K9me3 is rare (0.2%). H3K9me is controlled by DNA methylation and is not required for the formation of constitutive heterochromatin, but double methylation H3K9meK27me is required for the recruitment of CMT3 to methylate heterochromatin and silence euchromatic loci. Very low level of H3K9meK14ac. 36% of H3K27 is found under the form of H3K27me1 and 6% of H3K27me2, with no detectable H3K27me3. 6% of H3K36 is found under the form of H3K36me1, 15% of H3K36me2 and 3% of H3K36me3. H3K27me2K36me1 is found in 15% of the proteins while H3k27me1K36me2 is not detected. H2BK143ub1 is probably prerequisite for H3K4me. Elevated H3K4me3 and H3K36me2 formed by ASHH2 are required for high FLC expression. Vernalization increases H3K9me2 and H3K27me2/3 and decreases H3K4me2 at the FLC locus, resulting in the epigenetic silencing of this floral repressor. In meta- and anaphase, H3T11ph is found on the entire length of the condensed chromosomes, whereas H3S10ph and H3S28ph are confined to the pericentromeric regions. During the first meiotic division, H3S10ph and H3S28ph are found on the entire length of the chromosome. Both sites may be involved in sister chromatid cohesion. No phosphorylation detected during interphase. AUR1 and AUR2 phosphorylate only H3S10, while AUR3 phosphorylates both H3S10 and H3S28. 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; H3K9me1/2/3 = mono-, di- and trimethylated Lys-10; H3K9ac = acetylated Lys-10; H3S10ph = phosphorylated Ser-11; H3T11ph = phosphorylated Thr-12; H3K14ac = acetylated Lys-15; H3K18ac = acetylated Lys-19; H3K18me1 = monomethylated Lys-19; H3K23ac = acetylated Lys-24; H3K23me1 = monomethylated Lys-24; H3K27me1/2/3 = mono-, di- and trimethylated Lys-28; H3S28ph = phosphorylated Ser-29; H3K36me1/2/3 = mono-, di- and trimethylated Lys-37.