DNA repair proteins

Redox signaling between DNA repair proteins for efficient lesion detection

Published online before print August 31, 2009, doi: 10.1073/pnas.0908059106
PNAS September 8, 2009 vol. 106 no. 36

1. Amie K. Boala,
2. Joseph C. Genereuxa,
3. Pamela A. Sontza,
4. Jeffrey A. Gralnickb,
5. Dianne K. Newmanc,1 and
6. Jacqueline K. Bartona,1

+ Author Affiliations

1.
aDivision of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125;
2.
bDepartment of Microbiology, BioTechnology Institute, University of Minnesota, St. Paul, MN 55108; and
3.
cDepartments of Biology and Earth, Atomospheric and Planetary Science, and Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139

1.

Contributed by Jacqueline K. Barton, July 21, 2009 (received for review June 25, 2009)

Abstract

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.