Redox signaling between DNA repair proteins for efficient lesion detection
Base excision repair (BER) enzymes maintain the integrity of the genome, and in humans, BER mutations are associated with cancer. Given the remarkable sensitivity of DNA-mediated charge transport (CT) to mismatched and damaged base pairs, we have proposed that DNA repair glycosylases (EndoIII and MutY) containing a redox-active [4Fe4S] cluster could use DNA CT in signaling one another to search cooperatively for damage in the genome. Here, we examine this model, where we estimate that electron transfers over a few hundred base pairs are sufficient for rapid interrogation of the full genome. Using atomic force microscopy, we found a redistribution of repair proteins onto DNA strands containing a single base mismatch, consistent with our model for CT scanning. We also demonstrated in Escherichia coli a cooperativity between EndoIII and MutY that is predicted by the CT scanning model. This relationship does not require the enzymatic activity of the glycosylase. Y82A EndoIII, a mutation that renders the protein deficient in DNA-mediated CT, however, inhibits cooperativity between MutY and EndoIII. These results illustrate how repair proteins might efficiently locate DNA lesions and point to a biological role for DNA-mediated CT within the cell.
© 2009 by the National Academy of Sciences. Contributed by Jacqueline K. Barton, July 21, 2009 (received for review June 25, 2009). Published online before print August 31, 2009, doi: 10.1073/pnas.0908059106 We thank Sheila David (University of California, Davis), Jeffrey Miller (University of California, Los Angeles), Timothy O'Connor (City of Hope, Duarte, CA), and the Coli Genetic Stock Center (Yale University, New Haven, CT) for their generous donation of bacterial strains and plasmids. We are grateful to the National Institutes of Health for Grant GM49216 (to J.K.B.) and the Howard Hughes Medical Institute (to D.K.N.). A.K.B. thanks the Parsons Foundation for fellowship support. Author contributions: A.K.B., J.C.G., P.A.S., J.A.G., D.K.N., and J.K.B. designed research; A.K.B., J.C.G., and P.A.S. performed research; J.A.G. and D.K.N. contributed new reagents/analytic tools; A.K.B., J.C.G., P.A.S., and J.K.B. analyzed data; and A.K.B., J.C.G., P.A.S., and J.K.B. wrote the paper. The authors declare no conflict of interest. This article contains supporting information online at www.pnas.org/cgi/content/full/0908059106/DCSupplemental.
Published - Boal2009p5904P_Natl_Acad_Sci_Usa.pdf
Supplemental Material - 0908059106SI.pdf