Histone H3

Histone H3 is one of the five main histone proteins involved in the structure of chromatin in eukaryotic cells. Featuring a main globular domain and a long N-terminal tail, H3 is involved with the structure of the nucleosomes of the 'beads on a string' structure.

The N-terminal tail of histone H3 protrudes from the globular nucleosome core and can undergo several different types of epigenetic modifications that influence cellular processes. These modifications include the covalent attachment of methyl or acetyl groups to lysine and arginine amino acids and the phosphorylation of serine or threonine. Methylation of lysine9 has been associated with gene silencing and the formation of relatively inactive regions of DNA known as heterochromatin. Acetylation of histone H3 occurs at several different lysine positions in the histone tail and is performed by a family of enzymes known as Histone Acetyl Transferases (HATs). Acetylation of lysine14 is commonly seen in genes that are being actively transcribed into RNA. Other histone proteins involved: H1 H2A H2B H4