histone
Sign in to savethumb|300px|Schematic representation of the assembly of the core histones into the nucleosome In biology, histones are highly-basic proteins abundant in lysine and arginine residues that are found in eukaryotic cell nuclei and in most Archaeal phyla. They act as spools around which DNA winds to create structural units called nucleosomes. Nucleosomes in turn are wrapped into 30-nanometer fibers that form tightly packed chromatin. Histones prevent DNA from becoming tangled and protect it from DNA damage. In addition, histones play important roles in gene regulation and DNA replication. Without h
AI overview
Histones are proteins found in the nuclei of eukaryotic cells that act as spools around which DNA winds, helping to organize and protect the genetic material. They are essential for preventing DNA from becoming tangled, shielding it from damage, and controlling which genes are turned on or off in cells.
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Article
33 sectionsContents
- Classes and variants
- Structure
- Evolution and species distribution
- Function{{anchor|Histone modifications}}
- Compacting DNA strands
- Transcription
- Chromatin regulation
- Modification{{anchor|Histone_modification}}
- Chemistry
- Lysine methylation
- Glutamine serotonylation
- Arginine methylation
- Arginine citrullination
- Lysine acetylation
- Serine/threonine/tyrosine phosphorylation
- Effects on transcription
- Actively transcribed genes
- Repressed genes
- Bivalent promoters
- Other functions
- DNA damage repair
- Chromosome condensation
- Addiction
- Histone chaperones
- Chaperone networks
- Synthesis
- Yeast
- Metazoan
- Link between cell-cycle control and synthesis
- History
- See also
- References
- External links
thumb|300px|Schematic representation of the assembly of the core histones into the nucleosome In biology, histones are highly-basic proteins abundant in lysine and arginine residues that are found in eukaryotic cell nuclei and in most Archaeal phyla. They act as spools around which DNA winds to create structural units called nucleosomes. Nucleosomes in turn are wrapped into 30-nanometer fibers that form tightly packed chromatin. Histones prevent DNA from becoming tangled and protect it from DNA damage. In addition, histones play important roles in gene regulation and DNA replication. Without histones, unwound DNA in chromosomes would be very long. For example, each human cell has about 1.8 meters of DNA if completely stretched out; however, when wound about histones, this length is reduced to about 9 micrometers (0.009 mm) of 30 nm diameter chromatin fibers.
There are five families of histones, which are designated H1/H5 (linker histones), H2, H3, and H4 (core histones). The nucleosome core is formed of two H2A-H2B dimers and a H3-H4 tetramer. The tight wrapping of DNA around histones, is to a large degree, a result of electrostatic attraction between the positively charged histones and negatively charged phosphate backbone of DNA.