MYB Family Transcription Factors Jonathan Russell Rena Schweizer

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 Mike Rena 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? • All share a conserved MYB DNABinding Domain – Up to three imperfect repeats (Helix-Turn-Helix structure) of ~53 AA each –Three regularly spaced tryptophan residues –R 1, R 2, R 3 repeats –Subfamilies are classified by number of adjacent repeats (MYBR 1, R 2 R 3 type MYB, MYB 3)

What Motifs Do Mybs Employ? • Helix-turn-Helix structures are crucial to sequence specificity • HTH intercalates in major groove • Recognition by Cterminal helix

MYB Structure: R 2 R 3 Sub Family • Largest family characterized in plants • Both R 2 and R 3 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…