Histone

From WikiMD.com Medical Encyclopedia

Assembly of histones into a nucleosome

Histones are proteins found in eukaryotic cell nuclei, which package the DNA into structural units called nucleosomes.[1][2] They are the chief protein components of chromatin, the active component of chromosomes.

Histones act as spools around which DNA winds, and play a role in gene regulation. Without histones, the unwound DNA in chromosomes would be very long. For example, each human cell has about 1.8 meters of DNA, but wound on the histones it has about 90 millimeters of chromatin, which, when duplicated and condensed during mitosis, result in about 120 micrometers of chromosomes.[3]

Functions[edit | edit source]

Compacting DNA strands[edit | edit source]

Histones act as spools around which DNA winds. This packs in the large genomes of eukaryotes to fit inside cell nuclei. The compacted molecule is 40,000 times shorter than an unpacked molecule.

Chromatin regulation[edit | edit source]

DNA on outside winding round histone on inside. View from top through helical axis

Histones undergo changes which alter their interaction with DNA and nuclear proteins. Long-term changes in histone/DNA interaction cause epigenetic effects. Combinations of modifications are thought to constitute a code, the so-called histone code.[4][5] Histone modifications act in diverse biological processes such as gene regulation, DNA repair and chromosome condensation (mitosis).

Examples[edit | edit source]

Examples of histone modifications in transcription regulation include:

Type of
modification 		Histone
H3K4 H3K9 H3K14 H3K27 H3K79 H4K20 H2BK5
mono-methylation activation[6] activation[7] activation[7] activation[7][8] activation[7] activation[7]
di-methylation repression[9] repression[9] activation[8]
tri-methylation activation[10] repression[7] repression[7] activation,[8]
repression[7] 		repression[9]
acetylation activation[10] activation[10]

History[edit | edit source]

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.[11]

The discovery of the H5 histone appears to date back to 1970's.[12][13]

Conservation across species[edit | edit source]

Histones are found in the nuclei of eukaryotic cells, and in certain Archaea, namely Euryarchaea, but not in bacteria. Histone proteins are among the most highly conserved proteins in eukaryotes,[14] which suggests they are vital to the biology of the nucleus.[2]: 939  In contrast, mature sperm cells largely use protamines to package their genomic DNA, most likely to achieve an even higher packaging ratio.[15]

Core histones are highly conserved proteins, that is, there are very few differences among the amino acid sequences of the histone proteins of different species. Linker histone usually has more than one form within a species and is also less conserved than the core histones.

References[edit | edit source]

  1. ↑ Robert M., Collins dictionary of human biology, Glasgow:HarperCollins, 2006, ISBN 0-00-722134-7,
  2. ↑ 2.0 2.1 {{{last}}}, Cox, Michael; Nelson, David R.; Lehninger, Albert L, Lehninger principles of biochemistry, San Francisco:W.H. Freeman, 2005, ISBN 0-7167-4339-6,
  3. ↑ Redon C, Pilch D, Rogakou E, Sedelnikova O, Newrock K, Bonner W, Histone H2A variants H2AX and H2AZ, Curr. Opin. Genet. Dev., Vol. 12(Issue: 2), pp. 162–9, DOI: 10.1016/S0959-437X(02)00282-4, PMID: 11893489,
  4. ↑ Strahl BD, Allis CD, The language of covalent histone modifications, Nature, Vol. 403(Issue: 6765), pp. 41–5, DOI: 10.1038/47412, PMID: 10638745,
  5. ↑ Jenuwein T, Allis CD, Translating the histone code, Science, Vol. 293(Issue: 5532), pp. 1074–80, DOI: 10.1126/science.1063127, PMID: 11498575,
  6. ↑ Benevolenskaya EV, Histone H3K4 demethylases are essential in development and differentiation, Biochem. Cell Biol., Vol. 85(Issue: 4), pp. 435–43, DOI: 10.1139/o07-057, PMID: 17713579,
  7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 Barski A, Cuddapah S, Cui K, Roh TY, Schones DE, Wang Z, Wei G, Chepelev I, Zhao K, High-resolution profiling of histone methylations in the human genome, Cell, Vol. 129(Issue: 4), pp. 823–37, DOI: 10.1016/j.cell.2007.05.009, PMID: 17512414,
  8. ↑ 8.0 8.1 8.2 Steger DJ, Lefterova MI, Ying L, Stonestrom AJ, Schupp M, Zhuo D, Vakoc AL, Kim JE, Chen J, Lazar MA, Blobel GA, Vakoc CR, DOT1L/KMT4 recruitment and H3K79 methylation are ubiquitously coupled with gene transcription in mammalian cells, Mol. Cell. Biol., Vol. 28(Issue: 8), pp. 2825–39, DOI: 10.1128/MCB.02076-07, PMID: 18285465, PMC: 2293113,
  9. ↑ 9.0 9.1 9.2 Rosenfeld JA, Wang Z, Schones DE, Zhao K, DeSalle R, Zhang MQ, Determination of enriched histone modifications in non-genic portions of the human genome, BMC Genomics, 2009, Vol. 10, pp. 143, DOI: 10.1186/1471-2164-10-143, PMID: 19335899, PMC: 2667539,
  10. ↑ 10.0 10.1 10.2 Koch CM, Andrews RM, Flicek P, Dillon SC, Karaöz U, Clelland GK, Wilcox S, Beare DM, Fowler JC, Couttet P, James KD, Lefebvre GC, Bruce AW, Dovey OM, Ellis PD, Dhami P, Langford CF, Weng Z, Birney E, Carter NP, Vetrie D, Dunham I, The landscape of histone modifications across 1% of the human genome in five human cell lines, Genome Res., Vol. 17(Issue: 6), pp. 691–707, DOI: 10.1101/gr.5704207, PMID: 17567990, PMC: 1891331,
  11. ↑ Hulton CS, Seirafi A, Hinton JC, Sidebotham JM, Waddell L, Pavitt GD, Owen-Hughes T, Spassky A, Buc H, Higgins CF, Histone-like protein H1 (H-NS), DNA supercoiling, and gene expression in bacteria, Cell, Vol. 63(Issue: 3), pp. 631–42, DOI: 10.1016/0092-8674(90)90458-Q, PMID: 2171779,
  12. ↑ Crane-Robinson C, Dancy SE, Bradbury EM, Garel A, Kovacs AM, Champagne M, Daune M, Structural studies of chicken erythrocyte histone H5, Eur. J. Biochem., Vol. 67(Issue: 2), pp. 379–88, DOI: 10.1111/j.1432-1033.1976.tb10702.x, PMID: 964248,
  13. ↑ Aviles FJ, Chapman GE, Kneale GG, Crane-Robinson C, Bradbury EM, The conformation of histone H5. Isolation and characterisation of the globular segment, Eur. J. Biochem., Vol. 88(Issue: 2), pp. 363–71, DOI: 10.1111/j.1432-1033.1978.tb12457.x, PMID: 689022,
  14. ↑ Means: few or no changes between species
  15. ↑ Clarke HJ, Nuclear and chromatin composition of mammalian gametes and early embryos, Biochem. Cell Biol., 1992, Vol. 70(Issue: 10-11), pp. 856–66, DOI: 10.1139/o92-134, PMID: 1297351,
WikiMD
Navigation: Wellness - Encyclopedia - Health topics - Disease Index‏‎ - Drugs - World Directory - Gray's Anatomy - Keto diet - Recipes

Search WikiMD

Ad.Tired of being Overweight? Try W8MD's physician weight loss program.
Semaglutide (Ozempic / Wegovy and Tirzepatide (Mounjaro / Zepbound) available.
Advertise on WikiMD

WikiMD's Wellness Encyclopedia

Let Food Be Thy Medicine
Medicine Thy Food - Hippocrates

Medical Disclaimer: WikiMD is not a substitute for professional medical advice. The information on WikiMD is provided as an information resource only, may be incorrect, outdated or misleading, and is not to be used or relied on for any diagnostic or treatment purposes. Please consult your health care provider before making any healthcare decisions or for guidance about a specific medical condition. WikiMD expressly disclaims responsibility, and shall have no liability, for any damages, loss, injury, or liability whatsoever suffered as a result of your reliance on the information contained in this site. By visiting this site you agree to the foregoing terms and conditions, which may from time to time be changed or supplemented by WikiMD. If you do not agree to the foregoing terms and conditions, you should not enter or use this site. See full disclaimer.
Credits:Most images are courtesy of Wikimedia commons, and templates, categories Wikipedia, licensed under CC BY SA or similar.

Retrieved from "https://wikimd.com/w/index.php?title=Histone&oldid=1275657"

Contributors: Prab R. Tumpati, MD