Biological Physical Sciences Institute, University of York, York, United Kingdom; Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
Erik G Hedlund
Biological Physical Sciences Institute, University of York, York, United Kingdom
Rosmarie Friemann
Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
Stefan Hohmann
Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden; Department of Biology and Biological Engineering, Chalmers University of Technology, Göteborg, Sweden
Transcription is regulated through binding factors to gene promoters to activate or repress expression, however, the mechanisms by which factors find targets remain unclear. Using single-molecule fluorescence microscopy, we determined in vivo stoichiometry and spatiotemporal dynamics of a GFP tagged repressor, Mig1, from a paradigm signaling pathway of Saccharomyces cerevisiae. We find the repressor operates in clusters, which upon extracellular signal detection, translocate from the cytoplasm, bind to nuclear targets and turnover. Simulations of Mig1 configuration within a 3D yeast genome model combined with a promoter-specific, fluorescent translation reporter confirmed clusters are the functional unit of gene regulation. In vitro and structural analysis on reconstituted Mig1 suggests that clusters are stabilized by depletion forces between intrinsically disordered sequences. We observed similar clusters of a co-regulatory activator from a different pathway, supporting a generalized cluster model for transcription factors that reduces promoter search times through intersegment transfer while stabilizing gene expression.
