mybO - dictyBase/community-annotations GitHub Wiki
MybO appears to be related to DUO3, a conserved protein in land plants [Brownfield et al, Plant Cell 21 (2009(https://pubmed.ncbi.nlm.nih.gov/19638475). DUO3 is the first identifiable blast hit of myb0, and Arabidopsis DUO3 blasted against the Dicty proteome hits only mybO. Both conserved regions described by Brownfield et al in plant DUO3 are clearly identifiable in mybO, and most of the amino acid residues conserved in plants are present in the Dicty protein.
Plant DUO3 is a nuclear protein which plays a role in cell cycle progression in male germ cells (developing pollen); in DUO3 mutant germ cells the timing of S-phase appears unaffected but the cells either fail to enter mitosis or do so after a pronounced delay.
MybO is threefold overexpressed in a Dicty strain in which the retinoblastoma-like gene rblA has been disrupted (Doquang-Strasser et al, in preparation). Most genes associated with cell cycle progression, including both S-phase and mitotic genes, are overexpressed in this strain. It is tempting to suppose that myb0 regulates cell cycle genes in Dictyostelium.
There is no obvious ortholog of mybO in animals. In the human genome, Dicty mybO hits mybB. Blasted back to Dicty, however, human mybB hits Dicty mybA long before mybO.
Harry MacWilliams, March 2010
On closer examination, MybO appears to be related to both DUO3 of plants and Gon-4 of animals.
As indicated above, DUO3 regulates cell cycle progression in developing pollen and appear to be specifically necessary for mitosis, as mutant cells accumulate in G2, or become polyploid. DUO3 is expressed in somatic plant tissues mainly in meristerms, suggesting a role in cell proliferation, though it is apparently has no unique function in this case 19638475, 20514235.
In gon-4 (gonadless) mutants of_ C elegans_, the gonadal precursors Z1 and Z4 fail to divide. The reason is not known 11112335.
DUO3, Gon-4 share and MybO share two short sequence motifs, called the Gc1 and Gc2 regions.
Myb0 has an additional simlarity to DUO3 in the region between 876 and 1031, which is similar to the DUO3-conserved region 2. This is not present in Gon-4 proteins.
MybO contains an extended myb-like domain at its C-terminus. In this respect, MybO resembles Gon-4. Duo3 does not have a myb domain of any kind; however, it interacts with DUO1, which has an R2R3 class myb domain, a domain common to plants.
The myb-like domain of mybO is more similar to plant- than to animal myb domains, though Dicty also has animal-like mybs (such as mybA).
Harry MacWilliams, March 2011
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