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Oxidative stress inactivates the human DNA mismatch repair system


Chang, C L; Marra, G; Chauhan, D P; Ha, H T; Chang, D K (2002). Oxidative stress inactivates the human DNA mismatch repair system. American Journal of Physiology. Cell Physiology, 283(1):C148-C154.

Abstract

In the human DNA mismatch repair (MMR) system, hMSH2 forms the hMutSalpha and hMutSbeta complexes with hMSH6 and hMSH3, respectively, whereas hMLH1 and hPMS2 form the hMutLalpha heterodimer. These complexes, together with other components in the MMR system, correct single-base mismatches and small insertion/deletion loops that occur during DNA replication. Microsatellite instability (MSI) occurs when the loops in DNA microsatellites are not corrected because of a malfunctioning MMR system. Low-frequency MSI (MSI-L) is seen in some chronically inflamed tissues in the absence of genetic inactivation of the MMR system. We hypothesize that oxidative stress associated with chronic inflammation might damage protein components of the MMR system, leading to its functional inactivation. In this study, we demonstrate that noncytotoxic levels of H2O2 inactivate both single-base mismatch and loop repair activities of the MMR system in a dose-dependent fashion. On the basis of in vitro complementation assays using recombinant MMR proteins, we show that this inactivation is most likely due to oxidative damage to hMutSalpha, hMutSbeta, and hMutLalpha protein complexes. We speculate that inactivation of the MMR function in response to oxidative stress may be responsible for the MSI-L seen in nonneoplastic and cancer tissues associated with chronic inflammation.

In the human DNA mismatch repair (MMR) system, hMSH2 forms the hMutSalpha and hMutSbeta complexes with hMSH6 and hMSH3, respectively, whereas hMLH1 and hPMS2 form the hMutLalpha heterodimer. These complexes, together with other components in the MMR system, correct single-base mismatches and small insertion/deletion loops that occur during DNA replication. Microsatellite instability (MSI) occurs when the loops in DNA microsatellites are not corrected because of a malfunctioning MMR system. Low-frequency MSI (MSI-L) is seen in some chronically inflamed tissues in the absence of genetic inactivation of the MMR system. We hypothesize that oxidative stress associated with chronic inflammation might damage protein components of the MMR system, leading to its functional inactivation. In this study, we demonstrate that noncytotoxic levels of H2O2 inactivate both single-base mismatch and loop repair activities of the MMR system in a dose-dependent fashion. On the basis of in vitro complementation assays using recombinant MMR proteins, we show that this inactivation is most likely due to oxidative damage to hMutSalpha, hMutSbeta, and hMutLalpha protein complexes. We speculate that inactivation of the MMR function in response to oxidative stress may be responsible for the MSI-L seen in nonneoplastic and cancer tissues associated with chronic inflammation.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Molecular Cancer Research
07 Faculty of Science > Institute of Molecular Cancer Research
Dewey Decimal Classification:570 Life sciences; biology
Language:English
Date:2002
Deposited On:01 Oct 2010 12:51
Last Modified:05 Apr 2016 14:13
Publisher:American Physiological Society
ISSN:0363-6143
Free access at:Official URL. An embargo period may apply.
Publisher DOI:10.1152/ajpcell.00422.2001
Official URL:http://ajpcell.physiology.org/cgi/content/full/283/1/C148
PubMed ID:12055083
Permanent URL: http://doi.org/10.5167/uzh-35490

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