Myb
gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
s are part of a large
gene family
A gene family is a set of several similar genes, formed by duplication of a single original gene, and generally with similar biochemical functions. One such family are the genes for human hemoglobin subunits; the ten genes are in two clusters on ...
of
transcription factor
In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription (genetics), transcription of genetics, genetic information from DNA to messenger RNA, by binding t ...
s found in animals and plants. In humans, it includes
Myb proto-oncogene like 1 and
Myb-related protein B in addition to MYB proper.
Members of the extended SANT/Myb family also include the
SANT domain and other similar all-helical
homeobox
A homeobox is a Nucleic acid sequence, DNA sequence, around 180 base pairs long, that regulates large-scale anatomical features in the early stages of embryonic development. Mutations in a homeobox may change large-scale anatomical features of ...
-like domains.
Function
Viral
The Myb gene family is named after the eponymous gene in
Avian myeloblastosis virus
''Alpharetrovirus'' is a genus of viruses in the family ''Retroviridae
A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. After invad ...
. The viral Myb (v-Myb, ) recognizes the sequence 5'-
YAAC
KG-3'. It causes myeloblastosis (myeloid leukemia) in chickens. Compared to the normal animal cellular Myb (c-myb), v-myb contains deletions in the C-terminal regulatory domain, leading to aberrant activation of other oncogenes.
Animals
Myb proto-oncogene protein is a member of the MYB (myeloblastosis) family of
transcription factor
In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription (genetics), transcription of genetics, genetic information from DNA to messenger RNA, by binding t ...
s. The protein contains three domains, an
N-terminal
The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide, referring to the free amine group (-NH2) located at the end of a polypeptide. Within a peptide, the amin ...
DNA-binding domain
A DNA-binding domain (DBD) is an independently folded protein domain that contains at least one structural motif that recognizes double- or single-stranded DNA. A DBD can recognize a specific DNA sequence (a recognition sequence) or have a gener ...
, a central transcriptional activation domain and a C-terminal domain involved in transcriptional
repression. It may play a role in cell cycle regulation. Like the viral version, this gene is an
oncogene
An oncogene is a gene that has the potential to cause cancer. In tumor cells, these genes are often mutated, or expressed at high levels. , and rearrangements of the gene (often involving deletion in the C-terminal domain) causes cancer.
Plants
MYB factors represent a family of proteins that include the conserved MYB DNA-binding domain. Plants contain a MYB-protein subfamily that is characterised by the R2R3-type MYB domain.
In maize,
phlobaphene
Phlobaphenes (or phlobaphens, CAS No.:71663-19-9) are reddish, alcohol-soluble and water-insoluble phenolic substances. They can be extracted from plants, or be the result from treatment of tannin extracts with mineral acids (tanner's red). The na ...
s are synthesized in the flavonoids synthetic pathway
from polymerisation of
flavan-4-ol
The flavan-4-ols (3-deoxyflavonoids) are flavone-derived Alcohol (chemistry), alcohols and a family of flavonoids. Flavan-4-ols are colorless precursor compounds that polymerize to form red phlobaphene pigments. They can be found in the sorghum. Gl ...
s
which encodes an R2R3 myb-like
transcriptional activator
A transcriptional activator is a protein (transcription factor) that increases transcription of a gene or set of genes. Activators are considered to have ''positive'' control over gene expression, as they function to promote gene transcription and ...
of the A1 gene encoding for the
dihydroflavonol 4-reductase
In enzymology, a dihydrokaempferol 4-reductase () is an enzyme that catalyzes the chemical reaction
:cis-3,4-leucopelargonidin + NADP+ \rightleftharpoons (+)- dihydrokaempferol + NADPH + H+
Thus, the two substrates of this enzyme are cis-3,4 ...
(reducing
dihydroflavonol
The flavanonols (with two "o"s a.k.a. 3-hydroxyflavanone or 2,3-dihydroflavonol) are a class of flavonoid
Flavonoids (or bioflavonoids; from the Latin word ''flavus'', meaning yellow, their color in nature) are a class of polyphenolic second ...
s into flavan-4-ols)
while another gene (Suppressor of Pericarp Pigmentation 1 or SPP1) acts as a
suppressor
A silencer, also known as a sound suppressor, suppressor, or sound moderator, is a gun barrel#Muzzle, muzzle device that suppresses the muzzle blast, blast created when a gun (firearm or airgun) is discharged, thereby reducing the sound inten ...
. The maize P gene encodes a Myb homolog that recognizes the sequence CCWACC, in sharp contrast with the YAACGG bound by vertebrate Myb proteins.
In sorghum, the corresponding yellow seed 1 gene (y1)
[ ] also encodes a R2R3 type of Myb domain protein that regulates the expression of
chalcone synthase
Chalcone synthase or naringenin-chalcone synthase (CHS) is an enzyme ubiquitous to higher plants and belongs to a family of polyketide synthase enzymes (PKS) known as type III PKS. Type III PKSs are associated with the production of chalcones, a ...
,
chalcone isomerase
In enzymology, a chalcone isomerase () is an enzyme that catalyzes the chemical reaction
:a chalcone \rightleftharpoons a flavanone
Hence, this enzyme has one substrate, a chalcone, and one product, a flavanone.
This enzyme belongs to the fam ...
and
dihydroflavonol reductase
In enzymology, a dihydrokaempferol 4-reductase () is an enzyme that catalyzes the chemical reaction
:cis-3,4-leucopelargonidin + NADP+ \rightleftharpoons (+)-dihydrokaempferol + NADPH + H+
Thus, the two substrates of this enzyme are cis-3,4-le ...
genes required for the biosynthesis of
3-deoxyflavonoids
The flavan-4-ols (3-deoxyflavonoids) are flavone-derived alcohols and a family of flavonoids. Flavan-4-ols are colorless precursor compounds that polymerize to form red phlobaphene pigments. They can be found in the sorghum. Glycosides (abacopterin ...
.
Ruby is a MYB transcriptional activator of genes that produce
anthocyanin
Anthocyanins (), also called anthocyans, are solubility, water-soluble vacuole, vacuolar pigments that, depending on their pH, may appear red, purple, blue, or black. In 1835, the German pharmacist Ludwig Clamor Marquart named a chemical compou ...
in citrus fruits. In most citrus varieties Ruby is non-functional, but in blood oranges it upregulates anthocyanin production to produce the characteristic red color of the fruit.
See also
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EZH1
Histone-lysine N-methyltransferase EZH1 is an enzyme that in humans is encoded by the ''EZH1'' gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides ...
References
Further reading
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External links
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''Drosophila'' ''Myb oncogene-like'' - The Interactive Fly''Arabidospsis thaliana'' MYB family at Database of Arabidopsis Transcription Factors (DATF)
{{DEFAULTSORT:Myb (Gene)
Transcription factors
Human proteins