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- **********************************************************************
- * Myc-type, 'helix-loop-helix' putative DNA-binding domain signature *
- **********************************************************************
-
- A number of eukaryotic proteins, which probably are sequence specific DNA-
- binding proteins that act as transcription factors, share a conserved domain
- of 50 to 60 amino acid residues. It has been proposed [1] that this domain is
- formed of two amphipathic helices joined by a variable length linker region
- that could form a loop. This 'helix-loop-helix' domain has been found in the
- proteins listed below [2,3] (references are only provided for recently
- determined sequences).
-
- - The myc family of cellular oncogenes [4], which is currently known to
- contain four members: c-myc, N-Myc, L-myc, and B-myc. The myc genes are
- thought to play a role in cellular differentiation and proliferation.
- - Proteins involved in myogenesis (the induction of muscle cells). In mammals
- MyoD1 (Myf-3), myogenin (Myf-4), Myf-5, and Myf-6 (Mrf4 or herculin), in
- birds CMD1 (QMF-1), in Xenopus MyoD and MF25, in Caenorhabditis elegans
- CeMyoD, and in Drosophila nautilus (nau).
- - Vertebrate proteins that bind specific DNA sequences ('E boxes') in various
- immunoglobulin chains enhancers: E2A (E12), E47, ITF-1, ITF-2, TFE3, and
- TFEB.
- - Mammalian transcription factor HES-1, which repress transcription by acting
- on two types of DNA sequences, the E box and the N box.
- - Mammalian upstream stimulatory factor 1 (USF1), which binds to a
- symmetrical DNA sequence that is found in a variety of viral and cellular
- promoters.
- - Human lyl-1 protein; which is involved, by chromosomal translocation, in T-
- cell leukemia.
- - Mammalian stem cell protein (SCL) (also known as tal1), a protein which may
- play an important role in hemopoietic differentiation. SCL is involved, by
- chromosomal translocation, in stem-cell leukemia.
- - Mouse protein Id.
- - Mammalian AH receptor nuclear translocator (ARNT protein) [5]. This protein
- is required for the activity of the aryl hydrocarbon receptor; it
- associates with the ligand-binding subunit and acts as a transcriptional
- activator.
- - Drosophila achaete-scute (AS-C) complex proteins T3 (l'sc), T4 (scute),
- T5 (achaete) and T8 (asense). The AS-C proteins are involved in the
- determination of the neuronal precursors in the peripheral nervous system
- and the central nervous system.
- - Mammalian homologs of achaete-scute proteins, the MASH-1 and MASH-2
- proteins [6].
- - Drosophila twist (twi) protein, which is involved in the establishment of
- germ layers in embryos.
- - Drosophila daughterless (da) protein, which is essential for neurogenesis
- and sex-determination.
- - Drosophila hairy (h) protein, which acts in both segmentation and bristle
- patterning.
- - Drosophila extra-macrochaetae (emc) protein, which participates in sensory
- organ patterning by antagonizing the neurogenic activity of the achaete-
- scute complex.
- - Maize anthocyanin regulatory proteins R-S and LC.
- - Yeast centromere-binding protein 1 (CPF1 or CBF1). This protein is involved
- in chromosomal segregation. It binds to a highly conserved DNA sequence,
- found in centromers and in several promoters.
- - Yeast phosphate system positive regulatory protein PHO4 which interacts
- with the upstream activating sequence of several acid phosphatase genes.
- - Neurospora crassa nuc-1, a protein that activates the transcription of
- structural genes for phosphorus acquisition.
- - Fission yeast protein esc1 which is involved in the sexual differentiation
- process [6].
-
- The schematic representation of the helix-loop-helix domain is shown here:
-
- xxxxxxxxxxxxxxxxxxxxxxxx--------------------xxxxxxxxxxxxxxxxxxxxxxx
- Amphipathic helix 1 Loop Amphipathic helix 2
-
- The signature pattern we have developed to detect this domain spans completely
- the second amphipathic helix.
-
- -Consensus pattern: [DENSTAP]-K-[LIVMWAGN]-{FYWCPHKR}-[LIVT]-[LIV]-x(2)-
- [STAV]-[LIVMSTAC]-x-[VMFYH]-[LIVMTA]-{P}-{P}-[LIVMSR]
- -Sequences known to belong to this class detected by the pattern: ALL, except
- for rainbow trout c-myc.
- -Other sequence(s) detected in SWISS-PROT: 12.
- -Last update: June 1994 / Pattern and text revised.
-
- [ 1] Murre C., McCaw P.S., Baltimore D.
- Cell 56:777-783(1989).
- [ 2] Garrel J., Campuzano S.
- BioEssays 13:493-498(1991).
- [ 3] Kato G.J., Dang C.V.
- FASEB J. 6:3065-3072(1992).
- [ 4] Krause M., Fire A., Harrison S.W., Priess J., Weintraub H.
- Cell 63:907-919(1990).
- [ 5] Reyes H., Reisz-Porszasz S., Hankinson O.
- Science 256:1193-1195(1992).
- [ 6] Benton B.K., Read M.S., Okayama H.
- EMBO J. 12:135-143(1993).
-