MYB Family Transcription Factors
Jonathan Russell
Rena Schweizer
Mike Douglas
What is a Transcription Factor?
• Transcription factor –
any protein other than RNA
Polymerase that is required for
transcription
MYB Family
• Myeloblast ---> MYB (came from first identified MYB which was in an avian oncogene)
• 203 identified MYB-family transcription factors
• Found in Eukaryotes
Our Genes Within the Myb Family
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Mike
Jonathan
Jonathan
Mike
RenaRena
MYBFAMILY
PHYLOGENY
• What is the Structure
and Function of MYBs?
Jonathan’s Gene
Jonathan’s GeneEmily’s Gene
What is the Structure of MYB Proteins?
• All share a conserved MYB DNA-Binding Domain
– Up to three imperfect repeats (Helix-Turn-Helix structure) of ~53 AA each
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–Three regularly spaced tryptophan residues
–R1, R2, R3 repeats
–Subfamilies are classified by number of adjacent repeats (MYBR1, R2R3-type MYB, MYB3)
What Motifs Do Mybs Employ?
• Helix-turn-Helix structures are crucial to sequence specificity
• HTH intercalates in major groove
• Recognition by C-terminal helix
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MYB Structure: R2R3 Sub Family
• Largest family characterized in plants
• Both R2 and R3 required for sequence-specific binding
• Some redundancy of amino acid sequence, but flexibility in recognition
What are the functions of Plant MYB Proteins?
• Wide diversity of functions
• By no means fully characterized
• In general: regulate many aspects of plant metabolism and development
• But…– Some bind telomeric sequences, structural– Some are clearly transcription factors
(from circadian clock to root hair formation)
Proposed Plant MYB Functions
Vertebrates• Cellular proliferation• Expressed in actively dividing cells before
differentiationPlants• Control of secondary metabolism• Regulation of cell morphogenesis• Serving in signal transduction pathways
responding to plant growth regulators
Specific MYB Functions
Controlling Secondary Metabolism
• Phenylpropanoid metabolism (modifications of compounds derrived from phenylalinine)
• One branch resposible for the production of anthocyanins (major group of plant pigments)
Regulating Cellular Morphogenesis
• In petunia, essential for developing the conical form of petal epidermal cells
• In Arabidopsis, essential for differentiation of hair cells in leaf and stem
Signal Transduction Pathways
• Hormonal responses during seed development and germination
• In Arabidopsis and maize, activate genes to respond to dehydration and salt stress
For all categories, variations across plant species
The Future of MYB Experiments
• In order to characterize each MYB gene, mutation studies need to be performed
• This involves: knocking out specific genes and looking for resulting phenotypes…
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