Environment-specific combinatorial cis-regulation in synthetic promoters

Area of Science:

• Molecular Biology
• Systems Biology
• Genetics

Background:

• Cellular environments dynamically influence gene expression through complex regulatory networks.
• Cis-regulatory elements within gene promoters and control regions are critical for sensitive and specific transcriptional responses.

Purpose of the Study:

• To develop accurate models predicting gene expression levels based on combinations of cis-regulatory elements across diverse environments.
• To investigate the quantitative relationship between promoter architecture and resulting gene expression.

Main Methods:

• Construction of synthetic promoter libraries in yeast, featuring various combinations of transcription factor binding sites.
• Assaying promoter activity across four distinct environmental conditions.
• Development and application of thermodynamic models to correlate promoter sequences with expression data.

Main Results:

• Thermodynamic models explained at least 56% of expression variation across conditions for each synthetic promoter library.
• Changes in effective transcription factor concentrations were identified as a primary driver of regulated gene expression.
• Two binding sites were observed to switch regulatory roles (activator to repressor) due to competitive binding of multiple factors.

Conclusions:

• Simple shifts in transcription factor concentrations can explain many complex gene expression changes.
• Competition among transcription factors at binding sites enables large, steep expression changes in response to environmental cues.
• Thermodynamic modeling provides a robust framework for understanding cis-regulatory element function and gene regulation.