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:4/23/2014)... the source of a unique rhythmic sound, recorded for ... is the Antarctic minke whale ( Balaenoptera bonaerensis ). ... 1960s who thought it sounded like a duck, the ... the Southern Ocean, but its source has remained a ... team of researchers deployed acoustic tags on two Antarctic ...
(Date:4/23/2014)... Buenos Aires yesterday, Argentina joins the European Molecular ... The move strengthens the ties between the European ... Argentinian scientists access to EMBL,s world-class facilities and ... since its inception, fostering excellent life science research ... core of EMBL,s mission," says EMBL Director General ...
(Date:4/23/2014)... first cause of dementia and affects some 400,000 people ... been found. One of the reasons for this is ... cause alterations in nerve transmissions and the loss of ... from the Institute of Neuroscience at the Universitat Autnoma ... memory consolidation and were able to develop a gene ...
Breaking Biology News(10 mins):Scientists identify source of mysterious sound in the Southern Ocean 2Scientists identify source of mysterious sound in the Southern Ocean 3Loss of memory in Alzheimer's mice models reversed through gene therapy 2
... an obscure retrovirus derived from mice was the result ... tissue samples and lab experiments some dating back ... which scientists have questioned repeatedly over the last couple ... when the telltale signature of the virus, known as ...
... disabilities, along with their families, can look forward to ... Institute (DDI) at Wayne State University. The institute ... U.S. Administration for Children and Families. As a ... the development of inclusive communities and quality of life ...
... father,s symposium. This is a gathering of eagles," says ... E.E. Just Symposium. The conference is drawing some of ... September 27-29, 2012. Alexander is the newly appointed E.E. ... symposium celebrates the spirit of scientific courage and interdisciplinary ...
Cached Biology News:New study confirms erroneous link between XMRV and prostate cancer-contamination was the cause 2New study confirms erroneous link between XMRV and prostate cancer-contamination was the cause 3New study confirms erroneous link between XMRV and prostate cancer-contamination was the cause 4Wayne State receives $2.8 million grant from US Administration for Children and Families 2Wayne State receives $2.8 million grant from US Administration for Children and Families 3Science stars head to Dartmouth for the E.E. Just Symposium 2
Other biology definitionOther Tags