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In Vitro Selection of Engineered Transcriptional Repressors for Targeted Epigenetic Silencing

In Vitro Selection of Engineered Transcriptional Repressors for Targeted Epigenetic Silencing

Published on: May 5, 2023

TtgV represses two different promoters by recognizing different sequences.

Sandy Fillet¹, Marisela Vélez, Duo Lu

¹Department of Environmental Protection, EEZ-CSIC, Granada, Spain.

Journal of Bacteriology

|December 31, 2008

Summary

The TtgV repressor controls multidrug efflux pumps in Pseudomonas putida by binding to specific DNA sequences. Key residues in TtgV determine its differential binding to ttgD and ttgG operators, influencing pump gene expression.

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Area of Science:

Microbiology
Molecular Biology
Biochemistry

Background:

The multidrug efflux pumps ttgDEF and ttgGHI in Pseudomonas putida are regulated by the TtgV repressor.
TtgV exhibits differential binding affinities for the ttgD and ttgG operators, leading to distinct gene expression patterns.

Purpose of the Study:

To investigate the molecular mechanisms by which the TtgV repressor modulates the expression of ttgD and ttgG operons.
To identify specific residues within TtgV's DNA binding domain critical for operator recognition and differential binding.

Main Methods:

Alanine substitution mutagenesis of TtgV residues 47-64.
Electrophoretic mobility shift assays (EMSAs) to assess DNA binding.
In vivo expression analysis of ttgD and ttgG promoters.
Sequence analysis and 3D modeling of TtgV-DNA interactions.

Main Results:

TtgV recognizes an inverted repeat sequence in both ttgD and ttgG operators.
Specific TtgV residues (48, 50, 53, 54, 60, 61) are crucial for ttgG operator binding but not ttgD.
Residues R47, R52, L57, and T49 are essential for binding to both operators.
TtgV modulates expression through recognition of both common and distinct sequences in the promoters.

Conclusions:

TtgV employs specific amino acid residues to achieve differential binding to the ttgD and ttgG operators.
These differential interactions are key to regulating the expression of distinct multidrug efflux pumps.
Proposed model suggests critical TtgV residues interact with nucleotides in the DNA major groove.