Assembly and Dynamics of Transcription Initiation Complexes

Gene expression is essential for life and development, allowing the cell to modulate mRNA production in response to intrinsic and extracellular cues. Initiation of gene transcription requires a highly regulated molecular process to assemble multisubunit complexes into the preinitiation complex (PIC). Attempts to visualize these processes have been driven largely by electron microscopy, with near atomic-level resolution producing static snapshots complemented by low-resolution fluorescence cell imaging. Here, we review how new advances in superresolution single-molecule imaging in live cells can track transcription across vast spatiotemporal scales. We discuss how recent imaging research has fundamentally recast our understanding of PIC assembly from a stable, ordered process to one constantly in flux, dominated by multivalent weak interactions. We also discuss future advancements that will further expand our ability to measure PIC assembly in concert with cellular behavior, predict complex interactions computationally, and target undruggable transcription factors to treat human disease.