Visualizing the Search for Radiation-damaged DNA Bases in Real Time.
The Base Excision Repair (BER) pathway removes the vast majority of damages produced by ionizing radiation, including the plethora of radiation-damaged purines and pyrimidines. The first enzymes in the BER pathway are DNA glycosylases, which are responsible for finding and removing the damaged base. Although much is known about the biochemistry of DNA glycosylases, how these enzymes locate their specific damage substrates among an excess of undamaged bases has long remained a mystery. Here we describe the use of single molecule fluorescence to observe the bacterial DNA glycosylases, Nth, Fpg and Nei, scanning along undamaged and damaged DNA. We show that all three enzymes randomly diffuse on the DNA molecule and employ a wedge residue to search for and locate damage. The search behavior of theEscherichia coliDNA glycosylases likely provides a paradigm for their homologous mammalian counterparts.
Department of Microbiology and Molecular Genetics, The Markey Center for Molecular Genetics, The University of Vermont, 95 Carrigan Drive, Burlington, Vermont, 05405, USA.
Andrea J
AJ
Lee
Department of Microbiology and Molecular Genetics, The Markey Center for Molecular Genetics, The University of Vermont, 95 Carrigan Drive, Burlington, Vermont, 05405, USA.
Susan S
SS
Wallace
Base excision repair; DNA glycosylases; Glycosylase diffusion; Search for radiation damage; Single molecule fluorescence; Wedge residue