Histone gene

Histone Fold

The Histone Fold is a structural motif in proteins that is primarily associated with DNA packaging within the cell nucleus. This motif is characteristic of the histone protein family, which includes the core histones H2A, H2B, H3, and H4. The histone fold allows these proteins to dimerize and form the core of the nucleosome, the fundamental unit of chromatin.

Structure

The histone fold is a three-helix bundle structure, with the helices designated α1, α2, and α3. The α1 and α3 helices are antiparallel and are connected by a short loop, while the α2 helix is perpendicular to the other two and is connected to them by longer loops. This structure allows for the formation of a dimer through the interaction of the α2 and α3 helices of two histone proteins.

Function

The primary function of the histone fold is to facilitate the dimerization of histone proteins and the formation of the nucleosome core. The histone fold also plays a role in the interaction of the nucleosome with DNA, as it provides a surface for the binding of the DNA double helix. In addition, the histone fold is involved in the regulation of gene expression, as modifications to the histones can affect the accessibility of the DNA and thus the transcription of genes.

Evolution

The histone fold is highly conserved in eukaryotes, suggesting that it has a fundamental role in the organization and regulation of the genome. However, histone-like proteins with a histone fold have also been found in archaea, indicating that this motif may have an ancient evolutionary origin.

See also

• Histone
• Nucleosome
• Chromatin
• DNA packaging
• Gene expression