# UVR8 > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/UVR8 > Markdown URL: https://mediated.wiki/source/UVR8.md > Source: https://en.wikipedia.org/wiki/UVR8 > Source revision: 1329824804 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{Infobox nonhuman protein | Name = UVB-resistance protein UVR8 | image = 4dnw.png | width = | caption = Crystal structure of UVB-resistance protein UVR8.{{PDBe|4dnw}}; {{cite journal | vauthors = Wu D, Hu Q, Yan Z, Chen W, Yan C, Huang X, Zhang J, Yang P, Deng H, Wang J, Deng X, Shi Y | title = Structural basis of ultraviolet-B perception by UVR8 | journal = Nature | volume = 484 | issue = 7393 | pages = 214–9 |date=April 2012 | pmid = 22388820 | doi = 10.1038/nature10931 | bibcode = 2012Natur.484..214D | s2cid = 2971536 }} | Organism = ''[Arabidopsis thaliana](/source/Arabidopsis_thaliana)'' | TaxID = 3702 | Symbol = UVR8 | AltSymbols = | CAS_number = | CAS_supplemental = | DrugBank = | EntrezGene = 836506 | PDB = 4DNW | PDB_supplemental = [http://www.ebi.ac.uk/pdbe/searchResults.html?display=both&term=Q9FN03 More structures] | RefSeqmRNA = NM_125781 | RefSeqProtein = NP_201191 | UniProt = Q9XHD7 | ECnumber = | Chromosome = 5 | EntrezChromosome = NC_003076.8 | GenLoc_start = 25553758 | GenLoc_end = 25560247 }} '''UV-B resistance 8''' ('''UVR8''') also known as '''ultraviolet-B receptor UVR8''' is an [UV-B](/source/Ultraviolet) – [sensing](/source/Photoreceptor_protein) [protein](/source/protein) found in [plant](/source/plant)s and possibly other sources.{{cite journal | vauthors = Christie JM, Arvai AS, Baxter KJ, Heilmann M, Pratt AJ, O'Hara A, Kelly SM, Hothorn M, Smith BO, Hitomi K, Jenkins GI, Getzoff ED|author-link12=Elizabeth D. Getzoff | title = Plant UVR8 Photoreceptor Senses UV-B by Tryptophan-Mediated Disruption of Cross-Dimer Salt Bridges | journal = Science | volume = 335 | issue = 6075 | pages = 1492–6 | date = February 2012 | pmid = 22323738 | pmc = 3505452 | doi = 10.1126/science.1218091 |bibcode=2012Sci...335.1492C }} *{{lay source |template = cite web |url= http://www.physorg.com/news/2012-02-ultraviolet-molecule-yields-secrets.html|title = Ultraviolet protection molecule in plants yields its secrets|date= February 9, 2012 |website = PhysOrg }} It is responsible for sensing ultraviolet light in the range 280-315 [nm](/source/Nanometer) and initiating the plant stress response. It is most sensitive at 285nm, near the lower limit of UVB. UVR8 was first identified as a crucial mediator of a plant's response to UV-B in ''[Arabidopsis thaliana](/source/Arabidopsis_thaliana)'' containing a mutation in this protein. This plant was found to have a hypersensitivity to UV-B{{cite journal | vauthors = Kliebenstein DJ, Lim JE, Landry LG, Last RL | title = Arabidopsis UVR8 regulates ultraviolet-B signal transduction and tolerance and contains sequence similarity to human regulator of chromatin condensation 1 | journal = Plant Physiol. | volume = 130 | issue = 1 | pages = 234–43 | date = September 2002 | pmid = 12226503 | pmc = 166556 | doi = 10.1104/pp.005041 }} which damages DNA. UVR8 is thought to be a unique photoreceptor as it doesn't contain a prosthetic [chromophore](/source/chromophore) but its light-sensing ability is intrinsic to the molecule.{{cite journal | vauthors = Ulm R, Jenkins GI | title = Q&A: How do plants sense and respond to UV-B radiation? | journal = BMC Biol | volume = 13 | issue = | pages = 45 | date = June 2015 | pmid = 26123292 | pmc = 4484705 | doi = 10.1186/s12915-015-0156-y | doi-access = free }} [Tryptophan](/source/Tryptophan) (Trp) residue 285 has been suggested to act the UV-B sensor, while other Trp residues have been also seen to be involved (Trp233 > Trp337 > Trp94) although in-vivo data suggests that Trp285 and Trp233 are most important. == Evolution == Although the complete genome sequence is only available from a limited number of [angiosperm](/source/angiosperm)s, bioinformatic analysis suggests that there are a large number of UVR8 [ortholog](/source/ortholog)s. Both number and position of key residues seem to be well conserved among angiosperms but also other plant species (e.g., ''[Chlamydomonas reinhardtii](/source/Chlamydomonas_reinhardtii)'' and ''[Volvox carteri](/source/Volvox_carteri)''). The latter implies that UVR8 potentially appeared before the evolutionary split in vascular land plants which would be rational considering that at that time the amount of UV-B radiation that penetrated the earth surface was higher as the ozone layer was not fully developed, hence UV protection and acclimation would be of crucial importance.{{cite thesis | author = Rizzini L | title = UVR8: a plant UV-B photoreceptor | type = Ph.D. | chapter = 3.4 Evolutionary and Structural Considerations | chapter-url = http://www.freidok.uni-freiburg.de/volltexte/8048/pdf/PhD_thesis_Rizzini.pdf | year = 2010 | publisher = Albert-Ludwigs-Universität Freiburg }} == Structure == UVR8 is a [β-propeller](/source/beta-propeller) protein with 7 blade-shaped [β-sheets](/source/beta_sheet). It shares sequence homology with mammalian proteins involved in regulating [chromatin](/source/chromatin) condensation, for example the human [RCC1](/source/RCC1) gene product. In the dark state, UVR8 forms a [homodimer](/source/protein_dimer) that is localized in the [cytosol](/source/cytosol), but UV-B illumination induces the dissociation of UVR8 dimer to its respective [monomer](/source/monomer)s and translocation to the nucleus occurs.{{cite journal | vauthors = Cloix C, Jenkins GI | title = Interaction of the Arabidopsis UV-B-specific signaling component UVR8 with chromatin | journal = Mol Plant | volume = 1 | issue = 1 | pages = 118–28 | date = January 2008 | pmid = 20031919 | doi = 10.1093/mp/ssm012 | doi-access = free }} The dimer is held together via a complex [salt bridge](/source/Salt_bridge_(protein_and_supramolecular)) network. == Mechanism == Upon UV-B irradiation, light is absorbed by one or more Trp residues which are situated adjacent to [Arg](/source/arginine) residues which form salt bridges across the dimer interface. It is thought that this light absorption induces the disruption of the salt-bridges and thus leads to the molecule's monomerization.{{cite journal | vauthors = Rizzini L, Favory JJ, Cloix C, Faggionato D, O'Hara A, Kaiserli E, Baumeister R, Schäfer E, Nagy F, Jenkins GI, Ulm R | title = Perception of UV-B by the Arabidopsis UVR8 protein | journal = Science | volume = 332 | issue = 6025 | pages = 103–6 | date = April 2011 | pmid = 21454788 | doi = 10.1126/science.1200660 | bibcode = 2011Sci...332..103R | s2cid = 5037346 }} Following monomerization, UVR8 accumulates in the nucleus where it interacts with a protein called constitutively photomorphogenic 1 (COP1). COP1 is known to act as an [E3 Ubiquitin ligase](/source/E3_Ubiquitin_ligase) that targets key [transcription factor](/source/transcription_factor)s for [ubiquitination](/source/ubiquitination) and [proteasome](/source/proteasome)-mediated degradation. However, in the case of UVR8, it has been shown to act as a positive regulator of UVR8-mediated UV-B signalling.{{cite journal | vauthors = Jenkins GI | title = Signal transduction in responses to UV-B radiation | journal = Annu Rev Plant Biol | volume = 60 | pages = 407–31 | year = 2009 | pmid = 19400728 | doi = 10.1146/annurev.arplant.59.032607.092953 }} Upon UV-B illumination, UVR8 interacts via a [C-terminal](/source/C-terminal) 27 amino acid region with the [WD40 domain](/source/WD40_repeat) of COP1 in the nucleus,{{cite journal | vauthors = Cloix C, Kaiserli E, Heilmann M, Baxter KJ, Brown BA, O'Hara A, Smith BO, Christie JM, Jenkins GI | title = C-terminal region of the UV-B photoreceptor UVR8 initiates signaling through interaction with the COP1 protein | journal = Proc. Natl. Acad. Sci. U.S.A. | volume = 109 | issue = 40 | pages = 16366–70 | date = October 2012 | pmid = 22988111 | pmc = 3479605 | doi = 10.1073/pnas.1210898109 | bibcode = 2012PNAS..10916366C | doi-access = free }} which triggers the induction of ELONGATED HYPOCOTYL 5 (HY5) — a key transcription factor for several UV-B responsive genes, and overall results in UV-B acclimation.{{cite journal | vauthors = Heijde M, Ulm R | title = UV-B photoreceptor-mediated signalling in plants | journal = Trends Plant Sci. | volume = 17 | issue = 4 | pages = 230–7 | date = April 2012 | pmid = 22326562 | doi = 10.1016/j.tplants.2012.01.007 }} == References == {{Reflist|35em}} == External links == {{Refbegin}} *{{Cite web |url=http://www.scripps.edu/news/press/images/getzoff_libby/20120209getzoff_hires.html |title=Detailed picture of a UV-sensing protein |publisher=[Scripps Research Institute](/source/Scripps_Research_Institute) |date=9 February 2012}} * [http://www.ebi.ac.uk/pdbe-apps/quips?story=Sunhats Sunhats for plants] QUite Interesting PDB Structure article at [http://www.pdbe.org PDBe] *{{Cite journal|title = In Vivo Function of Tryptophans in the Arabidopsis UV-B Photoreceptor UVR8|journal = The Plant Cell|date = 2012-09-01|issn = 1532-298X|pmc = 3480300|pmid = 23012433|pages = 3755–3766|volume = 24|issue = 9|doi = 10.1105/tpc.112.101451|language = en|first1 = Andrew|last1 = O’Hara|first2 = Gareth I.|last2 = Jenkins}} {{Refend}} Category:Plant proteins --- Adapted from the Wikipedia article [UVR8](https://en.wikipedia.org/wiki/UVR8) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/UVR8?action=history)). 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