InterPro domain: IPR017930

The myb-type HTH domain is a DNA-binding, helix-turn-helix (HTH) domain of approximately 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 recognise 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 [ 3 ]. A single myb-type HTH DNA-binding domain occurs in TRF1 and TRF2.

The 3D-structure of the myb-type HTH domain forms three alpha-helices [ 4 ]. The second and third helices connected via a turn comprisethe helix-turn-helix motif. Helix 3 is termed the recognition helix as itbinds the DNA major groove, like in other HTHs.

1. Viral myb oncogene encodes a sequence-specific DNA-binding activity. Nature 335, 835-7
2. Drosophila and vertebrate myb proteins share two conserved regions, one of which functions as a DNA-binding domain. EMBO J. 6, 3085-90
3. The R2R3-MYB gene family in Arabidopsis thaliana. Curr. Opin. Plant Biol. 4, 447-56
4. Mechanism of c-Myb-C/EBP beta cooperation from separated sites on a promoter. Cell 108, 57-70