Histones

Histones are a family of proteins that play a crucial role in organizing DNA within the cell nucleus. They are the main protein components of chromatin, acting as spools around which DNA winds, and play a role in gene regulation.

Structure

Histones are small proteins with a high proportion of basic amino acids, lysine and arginine, that facilitate binding to the negatively charged DNA. They are among the most highly conserved proteins in eukaryotes, underscoring their important role in the biology of the cell.

Types

There are five major types of histones: H1/H5, H2A, H2B, H3, and H4. Histones H2A, H2B, H3 and H4 are known as the core histones, while histones H1 and H5 are known as the linker histones.

Function

The primary function of histones is to help package DNA into a compact, dense shape during interphase. They also play a role in gene regulation. Without histones, the unwound DNA in chromosomes would be very long (a length to width ratio of more than 10 million to 1 in human DNA).

Histone Modifications

Histone proteins can be modified by a large number of post-translational modifications including methylation, acetylation, phosphorylation, ubiquitination, sumoylation, ADP-ribosylation, and deimination. These modifications occur predominantly on the N-terminal tail domains protruding from the nucleosome core, but can also occur in the globular core region of the histones.

See Also

• Chromatin
• DNA
• Gene Regulation
• Post-Translational Modification

References

Histones Resources
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