Transcript The Structure of MYB Proteins

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
Mike
Rena
Rena
Jonathan
Jonathan
MYB
FAMILY
PHYLOGENY
• What is the
Structure
and Function
of MYBs?
Jonathan’s Gene
Emily’s Gene
Jonathan’s Gene
What is the Structure of MYB Proteins?
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–Three regularly spaced
tryptophan residues
–R1, R2, R3 repeats
–Subfamilies are classified
by number of adjacent
repeats (MYBR1, R2R3type MYB, MYB3)
• All share a conserved MYB DNABinding Domain
– Up to three imperfect repeats
(Helix-Turn-Helix structure) of
~53 AA each
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What Motifs Do Mybs Employ?
• Helix-turn-Helix
structures are crucial
to sequence
specificity
• HTH intercalates in
major groove
• Recognition by Cterminal helix
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MYB Structure: R2R3 Sub
Family
• Largest family characterized in plants
• Both R2 and R3 required for sequencespecific 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
differentiation
Plants
• Control of secondary metabolism
• Regulation of cell morphogenesis
• Serving in signal transduction pathways
responding to plant growth regulators
Specific MYB Functions
Controlling Secondary
Metabolism
Regulating Cellular
Morphogenesis
Signal Transduction
Pathways
•
•
In petunia, essential for
developing the conical
form of petal epidermal
cells
•
Hormonal responses
during seed development
and germination
•
In Arabidopsis, essential
for differentiation of hair
cells in leaf and stem
•
In Arabidopsis and
maize, activate genes to
respond to dehydration
and salt stress
•
Phenylpropanoid
metabolism
(modifications of
compounds derrived
from phenylalinine)
One branch resposible
for the production of
anthocyanins (major
group of plant pigments)
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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