The START domain potentiates HD-ZIPIII transcriptional activity
Aman Y Husbands1,2, Antje Feller3, Vasudha Aggarwal4
1Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA.
The Plant Cell
|March 2, 2023
Summary
The START domain of Class III Homeodomain-Leucine Zipper (HD-ZIPIII) transcription factors binds phospholipids, enhancing their DNA binding and transcriptional activity. This resolves a key mystery in plant development.
Area of Science:
- Plant Molecular Biology
- Evolutionary Developmental Biology
Background:
- Class III Homeodomain-Leucine Zipper (HD-ZIPIII) transcription factors are ancient regulators of plant development.
- The function and ligands of the HD-ZIPIII START domain have remained elusive for over two decades.
Purpose of the Study:
- To elucidate the function of the START domain in HD-ZIPIII transcription factors.
- To identify the ligands and mechanism by which the START domain regulates HD-ZIPIII activity.
Main Methods:
- Biochemical assays to test homodimerization and transcriptional activity.
- Phospholipid binding assays.
- Site-directed mutagenesis to assess the impact of conserved residues on DNA binding and function.
Main Results:
- The START domain promotes HD-ZIPIII homodimerization and increases transcriptional potency.
- The START domain binds various phospholipids.
- Mutations affecting ligand binding or conformational readout abolish HD-ZIPIII DNA-binding competence.
Conclusions:
- The START domain potentiates HD-ZIPIII transcriptional activity through phospholipid binding and ligand-induced conformational changes.
- This mechanism renders HD-ZIPIII dimers competent for DNA binding, resolving a long-standing question in plant development.
- The findings highlight the evolutionary flexibility of the START domain as a regulatory module.
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