Abstract
Until now, it has been difficult to establish exactly how a specific DNA lesion signals apoptosis because each DNA damaging agent produces a collection of distinct DNA lesions and produces damage in RNA, protein, and lipids. We have developed a system in human cells that focuses on the response to a single type of DNA lesion, namely O(6)-methylguanine (O(6)MeG). We dissect the signaling pathways involved in O(6)MeG-induced apoptosis, a response dependent on the MutSalpha heterodimer that is normally involved in DNA mismatch repair. O(6)MeG triggers robust activation of caspases associated with both death receptor- and mitochondrial-mediated apoptosis. Despite this, O(6)MeG/MutSalpha-triggered apoptosis is only partly dependent on caspase activation; moreover, it is mediated solely by mitochondrial signaling and not at all by death receptor signaling. Finally, while Bcl-2 and Bcl-x(L), negative regulators of mitochondrial-regulated apoptosis, could effectively block O(6)MeG/MutSalpha-dependent apoptosis, they were unable to prevent the cells from ultimately dying.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adenosine Triphosphatases / genetics
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Adenosine Triphosphatases / metabolism
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Apoptosis / physiology*
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Arabidopsis Proteins / metabolism
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism
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Base Pair Mismatch
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Caspase Inhibitors
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Caspases / metabolism
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Cell Line
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Cysteine Proteinase Inhibitors / metabolism
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DNA Damage*
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DNA Repair
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism
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Dose-Response Relationship, Drug
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Enzyme Activation
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Fas Ligand Protein
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Fatty Acid Desaturases / metabolism
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Guanosine / analogs & derivatives*
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Guanosine / metabolism*
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Humans
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Membrane Glycoproteins / metabolism
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Methylnitronitrosoguanidine / metabolism
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MutS DNA Mismatch-Binding Protein
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Proto-Oncogene Proteins c-bcl-2 / metabolism
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Signal Transduction / physiology*
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bcl-X Protein
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fas Receptor / metabolism
Substances
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Arabidopsis Proteins
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BCL2L1 protein, human
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Bacterial Proteins
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Caspase Inhibitors
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Cysteine Proteinase Inhibitors
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DNA-Binding Proteins
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FASLG protein, human
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Fas Ligand Protein
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Membrane Glycoproteins
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Proto-Oncogene Proteins c-bcl-2
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Recombinant Fusion Proteins
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bcl-X Protein
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fas Receptor
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Guanosine
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Methylnitronitrosoguanidine
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6'-O-methylguanosine
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Fatty Acid Desaturases
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Fad7 protein, Arabidopsis
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Caspases
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Adenosine Triphosphatases
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MutS DNA Mismatch-Binding Protein