Abstract
Strains of Escherichia coli which lack the dam-encoded adenine methylase are mutators due to a reduction in the efficiency of postreplication mismatch repair. In this study, we show that Dam(-) strains are also defective in very-short-patch repair, the system which corrects T/G mismatches arising from the deamination of 5-methylcytosine. This defect is associated with decreased levels of Vsr, the endonuclease which initiates short-patch repair. We also show that production of the dcm-encoded cytosine methylase is unaffected in Dam(-) strains. Since the dcm and vsr genes are cotranscribed, the regulation of Vsr by Dam is probably posttranscriptional.
MeSH terms
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5-Methylcytosine
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Adenosine Triphosphatases*
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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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Blotting, Western
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Cytosine / analogs & derivatives
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Cytosine / metabolism
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DNA Methylation
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DNA Repair Enzymes*
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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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Deamination
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Endodeoxyribonucleases / genetics*
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Endodeoxyribonucleases / metabolism
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Escherichia coli / genetics*
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Escherichia coli / metabolism
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Escherichia coli Proteins*
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MutL Proteins
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MutS DNA Mismatch-Binding Protein
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Mutation
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Site-Specific DNA-Methyltransferase (Adenine-Specific) / genetics*
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Site-Specific DNA-Methyltransferase (Adenine-Specific) / metabolism
Substances
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Bacterial Proteins
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DNA-Binding Proteins
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Escherichia coli Proteins
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MutL protein, E coli
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5-Methylcytosine
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Cytosine
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Dam methyltransferase
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Site-Specific DNA-Methyltransferase (Adenine-Specific)
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dam protein, E coli
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Endodeoxyribonucleases
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methyl-directed mismatch repair protein, E coli
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vsr endonuclease
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Adenosine Triphosphatases
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MutL Proteins
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MutS DNA Mismatch-Binding Protein
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MutS protein, E coli
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DNA Repair Enzymes