Nucleosome

The Nucleosome is the fundamental structural unit of chromatin in eukaryotic cells. It consists of approximately 147 base pairs of genomic DNA wrapped in a left-handed superhelix around a histone octamer (containing two copies each of histones H2A, H2B, H3, and H4). Linker DNA between nucleosomes may associate with histone H1, forming the chromatosome. The nucleosome provides the first level of DNA compaction, regulates gene accessibility, and acts as a dynamic signaling hub for chromatin-modifying proteins and epigenetic marks. Structural dynamics of nucleosome positioning and histone modifications are essential for controlling gene expression, DNA replication, repair, recombination, and overall genome stability. Aberrations in nucleosome structure or function contribute to cancer and other diseases that involve epigenetic dysregulation. Drugs targeting the nucleosome or associated epigenetic enzymes represent an active area of therapeutic development, although safety concerns remain concerning the non-specific effects on gene expression and chromatin state.

Other names

Nucleosome core particleChromatosome (when including linker histone H1)Histone-DNA complexNCPNucleosome particle

Epigenetic enzyme modulation: Drugs alter histone post-translational modifications, affecting nucleosome structure and gene expression; Chromatin accessibility alteration: Remodelers and inhibitors can reposition or evict nucleosomes, regulating DNA accessibility; Transcriptional regulation: Changing nucleosome dynamics to up- or down-regulate specific genes