Lack of correlation between binding of EcoRII methyltransferase to DNA duplexes containing mismatches and the promotion of C to T mutations.
The cytosine methyltransferases (MTases) M. HhaI and M. HpaII bind substrates in which the target cytosine is replaced by uracil or thymine, i.e. DNA containing a U:G or a T:G mismatch. We have extended this observation to the EcoRII MTase (M. EcoRII) and determined the apparent Kd for binding. Using a genetic assay we have also tested the possibility that MTase binding to U:G mismatches may interfere with repair of the mismatches and promote C:G to T:A mutations. We have compared two mutants of M. EcoRII that are defective for catalysis by the wild-type enzyme for their ability to bind DNA containing U:G or T:G mismatches and for their ability to promote C to T mutations. We find that although all three proteins are able to bind DNAs with mismatches, only the wild-type enzyme promotes C:G to T:A mutations in vivo. Therefore, the ability of M. EcoRII to bind U:G mismatched duplexes is not sufficient for their mutagenic action in cells.
Sheluho
D
D
Wayne State University, Department of Chemistry, Detroit, MI 48202, USA.
Yebra
M J
MJ
Khariwala
S S
SS
Bhagwat
A S
AS
D044503:5-Methylcytosine; D001665:Binding Sites; D003596:Cytosine / Q000031:analogs & derivatives / Q000378:metabolism; D019175:DNA Methylation; D004260:DNA Repair; D004269:DNA, Bacterial / Q000378:metabolism*; D015257:DNA-Cytosine Methylases / Q000235:genetics / Q000378:metabolism*; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D007612:Kanamycin / Q000494:pharmacology; D009154:Mutation; D009692:Nucleic Acid Heteroduplexes / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides / Q000378:metabolism; D017354:Point Mutation
D004269:DNA, Bacterial; D009692:Nucleic Acid Heteroduplexes; D009838:Oligodeoxyribonucleotides; D007612:Kanamycin; D044503:5-Methylcytosine; D003596:Cytosine; C029528:DNA modification methylase EcoRII; D015257:DNA-Cytosine Methylases