Histones

Proteins in the cell nucleus

Histones act as ‘spools’ around which the DNA strands wind in two coils. The nucleus of a human cell contains around 25 million spools, which pack the DNA with varying degrees of compaction: genes in densely packed sites are unreadable, whilst those in more loosely packed areas are active.

Cells can influence the degree of compaction in a targeted way through a range of histone modifications (including phosphorylation, acetylation and methylation). This process is one of the epigenetic regulatory mechanisms possible within the cell.