helix-loop-helix

ヘリックス・ループ・ヘリックス, HLH

WordNet

1. move in loops; "The bicycle looped around the tree"
2. anything with a round or oval shape (formed by a curve that is closed and does not intersect itself)
3. a flight maneuver; aircraft flies a complete circle in the vertical plane (同)loop-the-loop
4. an intrauterine device in the shape of a loop
5. a computer program that performs a series of instructions repeatedly until some specified condition is satisfied
6. an inner circle of advisors (especially under President Reagan); "hes no longer in the loop"
7. the basic pattern of the human fingerprint
8. make a loop in; "loop a rope" (同)intertwine
9. fasten or join with a loop; "He looped the watch through his belt"
10. fly loops, perform a loop; "the stunt pilot looped his plane"
11. a curve that lies on the surface of a cylinder or cone and cuts the element at a constant angle (同)spiral
12. type genus of the family Helicidae (同)genus Helix

PrepTutorEJDIC

1. (糸・ひも・針金などで作った)『輪』・輪状のもの;(輪状の)湾曲部・(宙返り飛行・スケートなどで描く)輪・ループ (ある条件が成立するまで繰り返し実行される，プログラム中に記述された一連の命令のこと)・仲間、影響｝を受け合う間柄・同列の立場・「keep誰々in the loop」として、「keep誰々informed：情報を（人）に絶えず提供し続ける、報告を（人）に欠かさない、（人）に逐次連絡する、（人）に常に通知する」・避妊リング; (鉄道・電線などの)環状線(loop line)・…‘を'輪にする,輪で囲む・…‘を'輪で結ぶ,輪で締める《+『up』+『名,』+『名』+『up』》・輪になる,輪を描く
2. らせん / らせん形のもの
3. 見よ,そら
4. 便所

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/03/29 03:40:20」(JST)

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[Wiki en表示]

basic helix-loop-helix DNA-binding domain
Basic helix-loop-helix structural motif of ARNT. Two α-helices (blue) are connected by a short loop (red).
Identifiers
Symbol	bHLH
Pfam	PF00010
InterPro	IPR001092
SMART	SM00353
PROSITE	PDOC00038
SCOP	1mdy
SUPERFAMILY	1mdy
CDD	cd00083
Available protein structures: Pfam structures PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

A basic helix-loop-helix (bHLH) is a protein structural motif that characterizes a family of transcription factors. It should not be confused with the helix-turn-helix domain.

Structure

The motif is characterized by two α-helices connected by a loop. In general, transcription factors including this domain are dimeric, each with one helix containing basic amino acid residues that facilitate DNA binding. In general, one helix is smaller, and, due to the flexibility of the loop, allows dimerization by folding and packing against another helix. The larger helix typically contains the DNA-binding regions. bHLH proteins typically bind to a consensus sequence called an E-box, CANNTG. The canonical E-box is CACGTG (palindromic), however some bHLH transcription factors, notably those of the bHLH-PAS family, bind to related non-palindromic sequences, which are similar to the E-box.

Examples

Examples of transcription factors containing a bHLH include:

• AhR
• Beta2/NeuroD1
• BMAL-1-CLOCK
• C-Myc, N-Myc
• MyoD
• Myf5
• Pho4
• HIF
• ICE1
• NPAS1, NPAS3, MOP5
• Scl, also known as Tal1
• proneural bHLH genes like p-CaMKII, and pSer(336)NeuroD.
• Scleraxis
• Neurogenins
• MAX
• OLIG1, OLIG2
• TCF4 (Transcription Factor 4)

bHLH transcription factors are often important in development or cell activity. BMAL1-Clock is a core transcription complex in the molecular circadian clock. Other genes, like c-Myc and HIF-1, have been linked to cancer due to their effects on cell growth and metabolism.

Regulation

Since many bHLH transcription factors are heterodimeric, their activity is often highly regulated by the dimerization of the subunits. One subunit's expression or availability is often controlled, whereas the other subunit is constitutively expressed. Many of the known regulatory proteins, such as the Drosophila extramacrochaetae protein, have the helix-loop-helix structure but lack the basic region, making them unable to bind to DNA on their own. They are, however, able to form heterodimers with proteins that have the bHLH structure, and inactivate their abilities as transcription factors.

History

• 1989: Murre et al. showed that dimers of various bHLH proteins bind to a short DNA motif (later called E-Box). This E-box consists of the DNA sequence CANNTG, where N can be any nucleotide.
• 1994: Harrison's and Pabo's groups crystallize bHLH proteins bound to E-boxes, demonstrating that the parallel 4-helix bundle motif loop orients the basic sequences to interact with specific nucleotides in the major groove of the E-box.
• 1994: Wharton et al. identified asymmetric E-boxes bound by a subset of bHLH proteins with PAS domains (bHLH-PAS proteins), including Single-minded (Sim) and the aromatic hydrocarbon receptor.
• 1995: Semenza's group identifies hypoxia-inducible factor (HIF) as a bHLH-PAS heterodimer that binds a related asymmetric E-box.
• 2009: Grove, De Masi et al., identified novel short DNA motifs, bound by a subset of bHLH proteins, which they defined as "E-box-like sequences". These are in the form of CAYRMK, where Y stands for C or T, R is A or G, M is A or C and K is G or T.

Human proteins with helix-loop-helix DNA-binding domain

AHR; AHRR; ARNT; ARNT2; ARNTL; ARNTL2; ASCL1; ASCL2; ASCL3; ASCL4; ATOH1; ATOH7; ATOH8; BHLHB2; BHLHB3; BHLHB4; BHLHB5; BHLHB8; CLOCK; EPAS1; FERD3L; FIGLA; HAND1; HAND2; HES1; HES2; HES3; HES4; HES5; HES6; HES7; HEY1; HEY2; HIF1A; ID1; ID2; ID3; ID4; KIAA2018; LYL1; MASH1; MATH2; MAX; MESP1; MESP2; MIST1; MITF; MLX; MLXIP; MLXIPL; MNT; MSC; MSGN1; MXD1; MXD3; MXD4; MXI1; MYC; MYCL1; MYCL2; MYCN; MYF5; MYF6; MYOD1; MYOG; NCOA1; NCOA3; NEUROD1; NEUROD2; NEUROD4; NEUROD6; NEUROG1; NEUROG2; NEUROG3; NHLH1; NHLH2; NPAS1; NPAS2; NPAS3; OAF1; OLIG1; OLIG2; OLIG3; PTF1A; SCL; SCXB; SIM1; SIM2; SOHLH1; SOHLH2; SREBF1; SREBF2; TAL1; TAL2; TCF12; TCF15; TCF21; TCF3; TCF4; TCFL5; TFAP4; TFE3; TFEB; TFEC; TWIST1; TWIST2; USF1; USF2;

References

External links

• PDOC00038 in PROSITE
• Basic Helix-Loop-Helix Transcription Factors at the US National Library of Medicine Medical Subject Headings (MeSH)
• bHLH family at PlantTFDB:Plant Transcription Factor Database

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

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English Journal

• CtBP and Associated LSD1 Are Required for Transcriptional Activation by NeuroD1 in Gastrointestinal Endocrine Cells.

• Ray SK1, Li HJ1, Metzger E2, Schüle R2, Leiter AB3.
• Molecular and cellular biology.Mol Cell Biol.2014 Jun 15;34(12):2308-2317. Epub 2014 Apr 14.
• Gene expression programs required for differentiation depend on both DNA-bound transcription factors and surrounding histone modifications. Expression of the basic helix-loop-helix (bHLH) protein NeuroD1 is restricted to endocrine cells in the gastrointestinal (GI) tract, where it is important for e
• PMID 24732800

• Transcriptional coordination between leaf cell differentiation and chloroplast development established by TCP20 and the subgroup Ib bHLH transcription factors.

• Andriankaja ME1, Danisman S, Mignolet-Spruyt LF, Claeys H, Kochanke I, Vermeersch M, De Milde L, De Bodt S, Storme V, Skirycz A, Maurer F, Bauer P, Mühlenbock P, Van Breusegem F, Angenent GC, Immink RG, Inzé D.
• Plant molecular biology.Plant Mol Biol.2014 Jun;85(3):233-45. doi: 10.1007/s11103-014-0180-2. Epub 2014 Feb 19.
• The establishment of the photosynthetic apparatus during chloroplast development creates a high demand for iron as a redox metal. However, iron in too high quantities becomes toxic to the plant, thus plants have evolved a complex network of iron uptake and regulation mechanisms. Here, we examined wh
• PMID 24549883

• Possible roles of basic helix-loop-helix transcription factors in adaptation to drought.

• Castilhos G1, Lazzarotto F1, Spagnolo-Fonini L2, Bodanese-Zanettini MH1, Margis-Pinheiro M3.
• Plant science : an international journal of experimental plant biology.Plant Sci.2014 Jun;223C:1-7. doi: 10.1016/j.plantsci.2014.02.010. Epub 2014 Mar 3.
• Water deficiency decreases plant growth and productivity. Several mechanisms are activated in response to dehydration that allows plants to cope with stress, including factors controlling stomatal aperture and ramified root system development. In addition, ABA metabolism is also implicated in the re
• PMID 24767109

Japanese Journal

• Helix-loop-helix Protein Id2 Stabilizes Mammalian Circadian Oscillation Under Constant Light Conditions

• Adachi Akihito A.,Fujioka Atsuko,Nagano Mamoru [他]
• Zoological science 30(12), 1011-1018, 2013-12
• NAID 40019900436

• Oscillatory Control of Factors Determining Multipotency and Fate in Mouse Neural Progenitors.

• Imayoshi Itaru,Isomura Akihiro,Harima Yukiko,Kawaguchi Kyogo,Kori Hiroshi,Miyachi Hitoshi,Fujiwara Takahiro,Ishidate Fumiyoshi,Kageyama Ryoichiro
• Science, 2013-10-31
• … 2013-11-01.The basic-helix-loop-helix transcription factors Ascl1/Mash1, Hes1, and Olig2 regulate fate choice of neurons, astrocytes, and oligodendrocytes, respectively. …
• NAID 120005343917

• Evolutionary Aspects of Variability in bHLH Orthologous Families : Insights from the Pearl Oyster, Pinctada fucata

• Gyoja Fuki,Satoh Nori
• Zoological science 30(10), 868-876, 2013-10
• NAID 40019826469

Related Links

• Basic helix-loop-helixとは - goo Wikipedia (ウィキペディア)

Structure [edit source | edit] The motif is characterized by two α-helices connected by a loop. In general, transcription factors including this domain are dimeric, each with one helix containing basic amino acid residues that facilitate DNA ...

• Helix loop helix | Flickr - Photo Sharing!

Supersecondary structure elements: Helix-loop-helix ... + Add ynse Member since 2006 Taken on September 21, 2008 1,455 Views 0 Galleries

Related Pictures

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「HLH」

　　[★]

• ヘリックス・ループ・ヘリックス helix-loop-helix
• 血球貪食性リンパ組織球症 hemophagocytic lymphohistiocytosis

「ヘリックス・ループ・ヘリックス」

　　[★]

英

helix-loop-helix、HLH

「helix-loop-helix motif」

　　[★]

ヘリックス・ループ・ヘリックス・モチーフ、HLHモチーフ

関

HLH motif

「basic helix-loop-helix leucine zipper transcription factor」

　　[★]

• ベーシック・ヘリックス・ループ・ヘリックスロイシンジッパー転写因子

「basic helix-loop-helix transcription factor」

　　[★]

• ベーシック・ヘリックス・ループ・ヘリックス型転写因子

「basic helix-loop-helix」

　　[★]

ベーシック・ヘリックス・ループ・ヘリックス

関

bHLH

「helix」

　　[★]

• n.

• らせん体、らせん、ヘリックス、(軟体動物)カタツムリ

関

helical、helices、snail、spiral

　 　

「loop」

　　[★]

• n.

• ループ、輪、蹄状紋、係蹄

関

ansa、ring、wheel