Myb

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

s are part of a large gene 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 of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The f ...

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-like domains.

Function

Viral

The Myb gene family is named after the eponymous gene in Avian myeloblastosis virus. The viral Myb (v-Myb, ) recognizes the sequence 5'-YAACKG-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

s. The protein contains three domains, an N-terminal

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 nam ...

s are synthesized in the flavonoids synthetic pathway from polymerisation of

flavan-4-ol 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 (abacopteri ...

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 flavonoids that use the 3-hydroxy-2,3-dihydro-2-phenylchromen-4-one (IUPAC name) backbone. Some examples include: * Taxifolin (or Dihydroquercetin) * ...

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 muzzle device that reduces the acoustic intensity of the muzzle report (sound of a gunshot) and muzzle rise when a gun (firearm or air gun) is discharged, b ...

. 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 ...

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 ...

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 (abacopteri ...

. Ruby is a MYB transcriptional activator of genes that produce anthocyanin 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.

References

External links

*
''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