Navigation Links
Histone


In biology, histones are the chief proteins of chromatin. They act as spools around which DNA winds and they play a role in gene regulation. Histones are found in the nuclei of eukaryotic cells. Bacteria do not have histones, but histones are found in certain Archaea, namely Euryarchaea. These archaeal histones may well resemble the evolutionary precursors to the eukaryotic histones.

Contents

Classes

Six histone classes are known:

  • H1 (sometimes called H5.)
  • H2A
  • H2B
  • H3
  • H4

Archaeal histones

Two each of class H2A, H2B, H3 and H4 assemble to form one nucleosome, together with DNA. H1 is needed for histone-DNA-complexes to form a 30-nm fiber, which packs the DNA even more tightly.

Functions

Histones act as spools around which DNA winds and they play a role in gene regulation. This enables the compaction necessary to fit the large genomes of eukaryotes inside cell nuclei. Histones act in gene regulation. Histones can undergo posttranslational modifications. These modifications can play a role in gene regulation in an epigenetic manner. Regulation occurs at the TATA box.

Structure

Histones are rich in lysine and arginine and are water-soluble. Histones are subject to posttranslational modification by enzymes primarily on their N-terminal tails, but also in their globular domains. Such modifications include methylation, acetylation, phosphorylation, ubiquitination, and ADP-ribosylation. This effects their function of gene regulation (see functions).

In general, genes that are active have less bound histone, while inactive genes are highly associated with histones during interphase. It also appears that the structure of histones have been evolutionarily conserved, as any deleterious mutations would be severely maladaptive.

History

Histones were discovered in 1884 by Albrecht Kossel. The word "histone" dates from the late 19th century and is from the German "Histon", of uncertain origin: perhaps from Greek histanai or from histos. Until the early 1990s, histones were dismissed as merely packing material for nuclear DNA. During the early 1990s, the regulatory functions of histones were discovered.

See also


'"/>


(Date:7/11/2014)... team of researchers from The Chinese University of Hong ... of wild soybean linked to salt tolerance, with implication ... soil. This study published online in Nature Communications ... information for crop improvement. , Soybean is an important ... selection, cultivated soybeans have less genetic diversities than their ...
(Date:7/11/2014)... group members to reduce aggression and gain access to ... grooming activities shows a certain pattern across the day. ... Biology Letters . , Grooming between individuals in ... motives. To be groomed has hygienic benefits and is ... can provide access to infants, mating opportunities and high ...
(Date:7/11/2014)... have explored two different ways that allow unprecedented ... the formation of oxygen molecules in photosynthesis. The ... journal Nature Communications . , "The new ... for water oxidation, which are key components for ... of solar energy in fuels like hydrogen, ethanol ...
Breaking Biology News(10 mins):BGI reports a novel gene for salt tolerance found in wild soybean 2Baboons groom early in the day to get benefits later 2Molecular snapshots of oxygen formation in photosynthesis 2
... are an important food source for fish and other aquatic ... this week in the Proceedings of the National Academy ... diets are supported by material that originates on land in ... to clarifying the role that watershed inputs play in aquatic ...
... BUFFALO, N.Y. -- An innovative, educational computing platform developed ... the cloud (remote, high-capacity, scalable servers) is helping UB ... new level. Soon, high-school and middle-school students will benefit ... by UB faculty members with a $250,000 National Science ...
... and Nanyang Technological University (NTU) are collaborating to enhance ... with oil., If successful, the wider application of the ... companies here to produce distilled water for their industrial ... at Singapore,s Jurong Island, which produce a lot of ...
Cached Biology News:Aquatic food web tied to land 2With cloud computing, the mathematics of evolution may get easier to learn 2With cloud computing, the mathematics of evolution may get easier to learn 3With cloud computing, the mathematics of evolution may get easier to learn 4memsys-NTU partnership to enhance water desalination technology 2
Other biology definitionOther Tags