Nucleosome (DNA–histone complex)

The DNA–histone complex, canonically termed the nucleosome, is the fundamental unit of eukaryotic chromatin composed of ~146–147 base pairs of DNA wrapped 1.6–1.7 turns around a histone octamer containing two copies each of H2A, H2B, H3, and H4; linker histone H1 binds DNA at the entry/exit to stabilize higher‑order structure. The octamer assembles from an H3–H4 tetramer and two H2A–H2B dimers, with flexible N‑terminal histone tails protruding and undergoing diverse post‑translational modifications that regulate chromatin accessibility and genomic functions including transcription, replication, and repair. While indispensable structurally and functionally, the nucleosome itself is not a discrete drug target like a receptor or enzyme; instead, therapeutic strategies typically address chromatin by modulating histone‑ or DNA‑modifying enzymes, readers, or remodelers, and by using nucleosome‑based biomarkers such as γH2AX to monitor DNA damage responses.

Other names

DNA–histone complexChromatin core particleNucleosome core particle (NCP)Chromatin nucleoprotein complex (contextual)