Transcription factor clusters regulate genes in eukaryotic cells

Area of Science:

• Molecular Biology
• Genetics
• Biophysics

Background:

• Gene transcription regulation relies on binding factors interacting with gene promoters.
• The precise mechanisms by which these factors locate their specific DNA targets remain largely unknown.
• Understanding transcription factor dynamics is crucial for deciphering gene expression control.

Purpose of the Study:

• To investigate the in vivo stoichiometry and spatiotemporal dynamics of the yeast repressor Mig1.
• To determine if Mig1 functions as individual molecules or in clusters.
• To elucidate the role of Mig1 clusters in gene regulation and promoter search.

Main Methods:

• Single-molecule fluorescence microscopy to track GFP-tagged Mig1 in Saccharomyces cerevisiae.
• 3D yeast genome modeling and simulations to analyze Mig1 cluster behavior.
• In vitro reconstitution and structural analysis of Mig1.
• Development of a promoter-specific fluorescent translation reporter.

Main Results:

• The repressor Mig1 operates in dynamic clusters within yeast cells.
• Upon extracellular signal detection, these clusters translocate from the cytoplasm to nuclear targets.
• Simulations and reporter assays confirmed that Mig1 clusters are the functional units of gene regulation.
• In vitro analysis suggests intrinsically disordered sequences stabilize these clusters via depletion forces.

Conclusions:

• Transcription factors, like Mig1, may function as clusters to enhance target search efficiency.
• This cluster model, involving intersegment transfer, potentially reduces promoter search times.
• Stabilization of gene expression is another key outcome of this clustered regulatory mechanism.
• Similar clustering was observed for a co-regulatory activator, suggesting a generalized model for transcription factors.