MYB was identified as the cellular homologue of v-myb, an oncogene found in two avian retroviruses (Avian Myeloblastosis Virus (AMV) and E26), which induce myeloblastic leukaemia and a mixed myeloid/erythroid leukaemia, respectively, in chickens.

The MYB gene spans 37.85 kb on the long arm of chromosome 6 and is transcribed in the centromere-to-telomere orientation.

Multiple splicing variants of ~2.9 to 3.6 kb encode a series of MYB proteins with identical DNA binding domains but unique C-terminal domains. The best characterized MYB variant is p89 with additional exon 9B.
The first intron contains an elongation attenuation region (Atn) which is important in regulating transcription of MYB.

The MYB protein consists of three distinct functional domains: an N-terminal helix-turn-helix (HTH)-type DNA binding domain (DBD), a centrally located trans-activation domain (TAD) and a C-terminal negative regulatory domain (NRD).
The DBD consists of three tandem 52 amino acid repeat termed R1, R2 and R3, which are involved in recognition and binding to the consensus sequence PyAACT/GG, known as the MYB binding site (MBS). MYBs trans-activation of its target genes requires the TAD. The NRD negatively regulates the trans-activating and transforming capacity of MYB. Several motifs within the NRD have been identified, including a Heptad Leucine Repeat (HLR) and a highly conserved EVES motif. Disruption of the HLR motif results in enhancement of MYBs trans-activating and transforming capacities. The EVES motif is also involved in negative regulation of MYBs activity by mediating interactions between the N-terminus and the C-terminus of the MYB protein.
MYB protein is subject to post-translational modifications, including ubiquitination, sumoylation, acetylation and phosphorylation.

MYB is expressed predominantly in immature progenitor cells of all haemopoietic lineages and these levels decrease as the cells progress towards terminal differentiation, although in differentiated T cells, MYB can be up-regulated upon activation.
Besides the haemopoietic system, MYB expression is also detected in colonic crypts and neurogenic niches.
MYB is highly expressed in almost all leukaemias. Overexpression of MYB is also detected in some solid tumors, such as breast cancer and colon cancer.

MYB is localized to the nucleus.

MYB mostly operates as a transcriptional activator. It binds to its cognate binding site (MYB binding site MBS; consensus A/C A A C G/T G) on target genes and regulates their expression.
MYB is essential for the establishment of definitive haemopoiesis; as such, myb^-/- mice die of anoxia by embryonic day 15. Conditional knockout mice have shown that myb is required at different stages of differentiation of the T and B lymphoid lineages. MYB is also reported to play a role in maintaining the haemopoietic stem cell pool. Interestingly, hypomorphic myb alleles result in an increase in platelet numbers in mouse models.
MYB is involved in maintaining the proliferation of progenitor cells. Knockdown of MYB in leukaemic cells and estrogen receptor positive breast cancer cells, where it is highly expressed, significantly slows down cell proliferation. Overexpressed or activated MYB suppresses normal differentiation and promotes leukaemic transformation. However, MYB also activates a number of haemopoietic-specific genes.

The MYB gene family contains the other two closely related members, MYBL1 (also known as A-MYB) and MYBL2 (also known as B-MYB).
The DBD is highly conserved between mammalian, chicken and drosophila MYB proteins, as well as MYBL1 and MYBL2. The MYB DBD also shares homology with other proteins, such as telomeric repeat binding factor -1, -2 (TRF1, TRF2) and cyclin D binding myb-like transcription factor 1 (DMTF1).