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BioMed Research International
Volume 2013, Article ID 152909, 9 pages
Research Article

The Effect of Msh2 Knockdown on Toxicity Induced by tert-Butyl-hydroperoxide, Potassium Bromate, and Hydrogen Peroxide in Base Excision Repair Proficient and Deficient Cells

1Centre for Occupational and Environmental Health, Institute of Population Health, Faculty of Medical and Human Sciences, University of Manchester, Manchester M13 9PT, UK
2School of Environment and Life Sciences, Cockcroft Building, University of Salford, Salford M5 4WT, UK

Received 18 April 2013; Revised 3 July 2013; Accepted 10 July 2013

Academic Editor: Nikhat J. Siddiqi

Copyright © 2013 N. Cooley et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The DNA mismatch repair (MMR) and base excision repair (BER) systems are important determinants of cellular toxicity following exposure to agents that cause oxidative DNA damage. To examine the interactions between these different repair systems, we examined whether toxicity, induced by t-BOOH and KBrO3, differs in BER proficient (Mpg+/+, Nth1+/+) and deficient (Mpg−/−, Nth1−/−) mouse embryonic fibroblasts (MEFs) following Msh2 knockdown of between 79 and 88% using an shRNA expression vector. Msh2 knockdown in Nth1+/+ cells had no effect on t-BOOH and KBrO3 induced toxicity as assessed by an MTT assay; knockdown in Nth1−/− cells resulted in increased resistance to t-BOOH and KBrO3, a result consistent with Nth1 removing oxidised pyrimidines. Msh2 knockdown in Mpg+/+ cells had no effect on t-BOOH toxicity but increased resistance to KBrO3; in Mpg−/− cells, Msh2 knockdown increased cellular sensitivity to KBrO3 but increased resistance to t-BOOH, suggesting a role for Mpg in removing DNA damage induced by these agents. MSH2 dependent and independent pathways then determine cellular toxicity induced by oxidising agents. A complex interaction between MMR and BER repair systems, that is, exposure dependent, also exists to determine cellular toxicity.