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Updated: Nov 23, 2025
Single-Molecule Fluorescence Visualization of DNA Polymerase Dynamics at G-Quadruplexes
Published on: April 4, 2025
Single-molecule fluorescence microscopy reveals modulation of DNA polymerase IV-binding lifetimes by UmuD (K97A) and
Sarah S Henrikus1,2,3, Antoine M van Oijen1,2, Andrew Robinson4,5
1Molecular Horizons Institute and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, 2522, Australia.
Abstract:
DNA polymerase IV (pol IV) is expressed at increased levels in Escherichia coli cells that suffer DNA damage. In a recent live-cell single-molecule fluorescence microscopy study, we demonstrated that the formation of pol IV foci is strongly recB-dependent in cells treated with the DNA break-inducing antibiotic ciprofloxacin. The results of that study support a model in which pol IV acts to extend D-loop structures during recombinational repair of DNA double-strand breaks. In the present study, we extend upon this work, investigating the UmuD and UmuD' proteins as potential modulators of pol IV activity in ciprofloxacin-treated cells. We found that the non-cleavable mutant UmuD(K97A) promotes long-lived association of pol IV with the nucleoid, whereas its cleaved form, UmuD', which accumulates in DNA-damaged cells, reduces binding. The results provide additional support for a model in which UmuD and UmuD' directly modulate pol IV-binding to the nucleoid.
