Lack of correlation between binding of EcoRII methyltransferase to DNA duplexes containing mismatches and the promotion of C to T mutations

• Published in: Molecular & general genetics Vol. 255; no. 1; pp. 54 - 59
• Main Authors: Sheluho, D, Yebra, M J, Khariwala, S S, Bhagwat, A S
• Format: Journal Article
• Language: English
• Published: Germany 01.06.1997
• Subjects: 5-Methylcytosine; Binding Sites; Cytosine - analogs & derivatives; Cytosine - metabolism; DNA Methylation; DNA Repair; DNA, Bacterial - metabolism; DNA-Cytosine Methylases - genetics; DNA-Cytosine Methylases - metabolism; Drug Resistance, Microbial; Escherichia coli - drug effects; Escherichia coli - enzymology; Escherichia coli - genetics; Kanamycin - pharmacology; Mutation; Nucleic Acid Heteroduplexes - metabolism; Oligodeoxyribonucleotides - metabolism; Point Mutation
• ISSN: 0026-8925
• DOI: 10.1007/s004380050474

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.