Abstract
Mammalian mismatch repair has been implicated in mismatch correction, the prevention of mutagenesis and cancer, and the induction of genotoxicity and apoptosis. Here, we show that treatment of cells specifically with agents inducing O(6)-methylguanine in DNA, such as N-methyl-N'-nitro-N-nitrosoguanidine and N-methyl-N-nitrosourea, elevates the level of MSH2 and MSH6 and increases GT mismatch binding activity in the nucleus. This inducible response occurs immediately after alkylation, is long-lasting and dose-dependent, and results from translocation of the preformed MutSalpha complex (composed of MSH2 and MSH6) from the cytoplasm into the nucleus. It is not caused by an increase in MSH2 gene activity. Cells expressing the DNA repair protein O(6)-methylguanine-DNA methyltransferase (MGMT), thus having the ability to repair O(6)-methylguanine, showed no translocation of MutSalpha, whereas inhibition of MGMT by O(6)-benzylguanine provoked the translocation. The results demonstrate that O(6)-methylguanine lesions are involved in triggering nuclear accumulation of MSH2 and MSH6. The finding that treatment of cells with O(6)-methylguanine-generating mutagens results in an increase of MutSalpha and GT binding activity in the nucleus indicates a novel type of genotoxic stress response.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Active Transport, Cell Nucleus / drug effects
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Adaptor Proteins, Signal Transducing
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Adenosine Triphosphatases*
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Alkylating Agents / pharmacology*
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Base Pair Mismatch / genetics
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Carrier Proteins
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Cell Line
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Cell Nucleus / drug effects*
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Cell Nucleus / enzymology
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Cell Nucleus / metabolism*
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Cytoplasm / drug effects
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Cytoplasm / metabolism
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DNA / chemistry
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DNA / genetics
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DNA / metabolism
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DNA Damage / drug effects
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DNA Methylation / drug effects
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DNA Repair / genetics*
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DNA Repair Enzymes*
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DNA-Binding Proteins / deficiency
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Gene Expression Regulation / drug effects
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Guanine / analogs & derivatives
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Guanine / metabolism
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HeLa Cells
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Humans
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Methylnitronitrosoguanidine / pharmacology
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Methylnitrosourea / pharmacology
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Mismatch Repair Endonuclease PMS2
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MutL Protein Homolog 1
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MutS Homolog 2 Protein
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Neoplasm Proteins / genetics
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Neoplasm Proteins / metabolism
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Nuclear Proteins
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O(6)-Methylguanine-DNA Methyltransferase / antagonists & inhibitors
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O(6)-Methylguanine-DNA Methyltransferase / metabolism
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Protein Binding
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Proto-Oncogene Proteins / genetics
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Proto-Oncogene Proteins / metabolism*
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RNA Stability / drug effects
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RNA, Messenger / genetics
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RNA, Messenger / metabolism
Substances
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Adaptor Proteins, Signal Transducing
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Alkylating Agents
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Carrier Proteins
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DNA-Binding Proteins
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G-T mismatch-binding protein
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MLH1 protein, human
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Neoplasm Proteins
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Nuclear Proteins
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Proto-Oncogene Proteins
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RNA, Messenger
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Methylnitronitrosoguanidine
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Guanine
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Methylnitrosourea
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DNA
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O-(6)-methylguanine
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O(6)-Methylguanine-DNA Methyltransferase
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Adenosine Triphosphatases
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PMS2 protein, human
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MSH2 protein, human
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Mismatch Repair Endonuclease PMS2
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MutL Protein Homolog 1
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MutS Homolog 2 Protein
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DNA Repair Enzymes