A simple assay for monitoring the mutagenic effects of 5-methylcytosine deamination in Escherichia coli.
We have developed and tested a simple phenotypic assay which monitors C to T transition mutations at the second C of a CCAGG sequence in the lacZ gene of Escherichia coli. The assay is based on new data concerning amino acid requirements on either side of a crucial active site residue in beta-galactosidase, glutamic acid 461. We show that the frequency of occurrence of the mutation is influenced by two genes: dcm, the cytosine methylase gene, and vsr, one of the genes involved in very short patch repair. The assay has been used to evaluate the function of vsr cloned from a potential very short patch repair mutant.
Petropoulos
L
L
Biology Department, Concordia University, Montréal, Qué., Canada.
Vidmar
J J
JJ
Passi
E
E
Cupples
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CG
D044503:5-Methylcytosine; D000595:Amino Acid Sequence; D001483:Base Sequence; D003596:Cytosine / Q000031:analogs & derivatives* / Q000378:metabolism; D004252:DNA Mutational Analysis / Q000379:methods*; D004260:DNA Repair; D015257:DNA-Cytosine Methylases / Q000235:genetics*; D003641:Deamination; D004706:Endodeoxyribonucleases / Q000235:genetics*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D007763:Lac Operon; D008745:Methylation; D008969:Molecular Sequence Data; D017354:Point Mutation; D013489:Suppression, Genetic
D044503:5-Methylcytosine; D003596:Cytosine; D015257:DNA-Cytosine Methylases; D004706:Endodeoxyribonucleases; C071421:vsr endonuclease