The myb family can be classified into three groups: the myb-type HTH domain,
which binds DNA, the SANT domain, which is a protein-protein interaction
module (see <PDOC51293>) and the myb-like domain that can be involved in
either of these functions.
The myb-type HTH domain is a DNA-binding, helix-turn-helix (HTH) domain of ~55
amino acids, typically occurring in a tandem repeat in eukaryotic
transcription factors. The domain is named after the retroviral oncogene
v-myb, and its cellular counterpart c-myb, which encode nuclear DNA-binding
proteins that specifically recognize the sequence YAAC(G/T)G [1,2]. Myb
proteins contain three tandem repeats of 51 to 53 amino acids, termed R1, R2
and R3. This repeat region is involved in DNA-binding and R2 and R3 bind
directly to the DNA major groove. The major part of the first repeat is
missing in retroviral v-Myb sequences and in plant myb-related (R2R3) proteins
. A single myb-type HTH DNA-binding domain occurs in TRF1 and TRF2.
The 3D-structure of the myb-type HTH domain forms three α-helices (see
<PDB:1H88; C>) . The second and third helices connected via a turn comprise
the helix-turn-helix motif. Helix 3 is termed the recognition helix as it
binds the DNA major groove, like in other HTHs.
Some proteins known to contain a myb-type HTH domain:
- Fruit fly myb protein .
- Vertebrate myb-like proteins A-myb and B-myb.
- Maize anthocyanin regulatory C1 protein, a trans-acting factor which
controls the expression of genes involved in anthocyanin biosynthesis.
- Maize P protein , a trans-acting factor which regulates the biosynthetic
pathway of a flavonoid-derived pigment in certain floral tissues.
- Arabidopsis thaliana protein GL1/GLABROUS1 , required for the initiation
of differentiation of leaf hair cells (trichomes).
- Maize and barley myb-related proteins Zm1, Zm38 and Hv1, Hv33 .
- Yeast BAS1 , a transcriptional activator for the HIS4 gene.
- Yeast REB1 , which recognizes sites within both the enhancer and the
promoter of rRNA transcription, as well as upstream of many genes
transcribed by RNA polymerase II.
- Fission yeast cdc5, a possible transcription factor whose activity is
required for cell cycle progression and growth during G2.
- Fission yeast myb1, which regulates telomere length and function.
- Baker's yeast pre-mRNA-splicing factor CEF1.
- Vertebrate telomeric repeat-binding factors 1 and 2 (TRF1/2), which bind to
telomeric DNA and are involved in telomere length regulation.
We have developed a profile, which has been manually adapted to specifically
detect the DNA-binding myb-type HTH domain. A second general profile was
developed for detection of the myb-like domain with a high sensitivity. A
third profile was developed for the SANT domain (see <PDOC51293>).
The profiles are in competition with one another and with the profile
of the SANT domain (see <PDOC51293>).
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