UMMS Affiliation
Graduate School of Biomedical Sciences; Department of Biochemistry and Molecular Pharmacology
Publication Date
2005-06-24
Document Type
Article
Disciplines
Life Sciences | Medicine and Health Sciences
Abstract
DNA mismatch repair (MMR) sensitizes human and Escherichia coli dam cells to the cytotoxic action of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) while abrogation of such repair results in drug resistance. In DNA methylated by MNNG, MMR action is the result of MutS recognition of O6-methylguanine base pairs. MutS and Ada methyltransferase compete for the MNNG-induced O6-methylguanine residues, and MMR-induced cytotoxicity is abrogated when Ada is present at higher concentrations than normal. To test the hypothesis that MMR sensitization is due to decreased recombinational repair, we used a RecA-mediated strand exchange assay between homologous phiX174 substrate molecules, one of which was methylated with MNNG. MutS inhibited strand transfer on such substrates in a concentration-dependent manner and its inhibitory effect was enhanced by MutL. There was no effect of these proteins on RecA activity with unmethylated substrates. We quantified the number of O6-methylguanine residues in methylated DNA by HPLC-MS/MS and 5-10 of these residues in phiX174 DNA (5386 bp) were sufficient to block the RecA reaction in the presence of MutS and MutL. These results are consistent with a model in which methylated DNA is perceived by the cell as homeologous and prevented from recombining with homologous DNA by the MMR system.
DOI of Published Version
10.1093/nar/gki673
Source
Nucleic Acids Res. 2005 Jun 22;33(11):3591-7. Link to article on publisher's site
Journal/Book/Conference Title
Nucleic acids research
Related Resources
PubMed ID
15972855
Repository Citation
Calmann MA, Evans JE, Marinus MG. (2005). MutS inhibits RecA-mediated strand transfer with methylated DNA substrates. GSBS Student Publications. https://doi.org/10.1093/nar/gki673. Retrieved from https://escholarship.umassmed.edu/gsbs_sp/167