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Ehrlichia chaffeensis TRP120 nucleomodulin binds DNA with disordered tandem repeat domain.
Valerie J Klema1, Krishna Mohan Sepuru1, Nadia Füllbrunn1
1Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, Texas, United States of America.
Plos One
|April 12, 2018
Summary
Ehrlichia chaffeensis effector protein TRP120 binds DNA via its tandem repeat regions. This interaction, requiring acidic conditions, induces TRP120 to fold, enabling gene expression modulation.
Area of Science:
- Microbiology
- Molecular Biology
- Structural Biology
Background:
- Ehrlichia chaffeensis causes human monocytotropic ehrlichiosis by secreting effector proteins.
- TRP120, a large effector protein, translocates to the host nucleus but lacks typical transcription factor domains.
- The mechanism of TRP120 DNA binding and gene modulation is unknown.
Purpose of the Study:
- To investigate the DNA-binding mechanism of Ehrlichia chaffeensis TRP120.
- To characterize the solution structure and DNA-binding ability of TRP120 tandem repeat regions.
Main Methods:
- Expression and purification of TRP120 tandem repeat (TR) constructs.
- Circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy for structural analysis.
- NMR spectroscopy to determine DNA-binding specificity and conditions.
Main Results:
- TRP120 (1 or 2 TR repeats) is a monomer and largely disordered in solution.
- TRP120 selectively binds GC-rich DNA at acidic pH.
- Acidic pH alone did not alter TRP120 structure, indicating folding upon DNA binding.
Conclusions:
- TRP120's tandem repeat regions are crucial for its DNA interaction.
- The folding of TRP120 is coupled to its DNA binding, a novel mechanism for transcription modulation.
- This study elucidates a potential mechanism for how Ehrlichia chaffeensis manipulates host gene expression.
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