histonen

Histonen is the term used in some European languages for the histone proteins, a family of small, highly basic nuclear proteins that package DNA into chromatin in eukaryotic cells. They are among the most conserved proteins in biology, reflecting their essential role in genome organization and regulation.

The core histonen—H2A, H2B, H3, and H4—assemble into an histone octamer that wraps about 147 base pairs of DNA to form the nucleosome, the fundamental unit of chromatin. The linker histone H1 binds to the DNA between nucleosomes and promotes higher-order chromatin compaction.

Histonen exist as variants that replace canonical histones in specific chromatin contexts. Examples include H2A.Z, H3.3, and CenH3 (CENP-A), which influence transcription, replication timing, and centromere identity. The supply and incorporation of histonen are coordinated with the cell cycle through histone chaperones and chromatin remodelers.

Post-translational modifications of histone tails—such as acetylation, methylation, phosphorylation, and ubiquitination—regulate chromatin accessibility and recruit effector proteins, creating epigenetic landscapes. Common marks include acetylation associated with active chromatin and methylation marks linked to activation or repression, depending on the residue and context.

Dysregulation of histonen content or modification patterns is linked to developmental disorders and cancer; histone-modifying enzymes are active targets in therapeutic research, with several inhibitors in clinical use or trials.

Historically, histonen were identified in early chromatin studies, and the nucleosome structure was clarified in the late 1990s. Histonen genes are present in virtually all eukaryotes and often exist in multiple copies to meet demands during DNA replication and cell division.