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Relationship between DNA methylation and mutational patterns induced by a sequence selective minor groove methylating
1Eppley Institute for Research in Cancer, University of Nebraska Medical Center, Omaha, Nebraska 69198-6805, USA.
The Journal of Biological Chemistry
|June 22, 1999
Summary
Me-lex preferentially forms N3-methyladenine (3-MeA) DNA adducts. While expected to be cytotoxic, this study reveals 3-MeA is also premutagenic, causing specific AT-targeted mutations in a sequence-dependent manner.
Area of Science:
- Chemical Biology
- Molecular Toxicology
- Genetics
Background:
- Me-lex is a novel DNA alkylating agent designed to induce N3-methyladenine (3-MeA) adducts.
- These 3-MeA adducts were hypothesized to be primarily cytotoxic rather than mutagenic DNA lesions.
Purpose of the Study:
- To determine the sequence specificity of DNA alkylation by Me-lex.
- To establish the mutagenic and lethal properties of Me-lex-induced DNA lesions.
Main Methods:
- Sequence specificity analysis of Me-lex in p53 cDNA using single strand breaks and sequencing gel electrophoresis.
- Assessing mutagenicity and cytotoxicity in a yeast system by transfecting Me-lex-treated p53 cDNA into a reporter strain.
Main Results:
- Me-lex predominantly (>99%) generated 3-MeA adducts, with methylation occurring at A bases within or adjacent to lex equilibrium binding sites.
- Distamycin inhibited methylation at minor groove sites.
- Mutational analysis revealed that 3-MeA lesions are premutagenic, leading to base pair substitutions, predominantly AT to TA transversions, at specific sequence contexts (e.g., A600-602 in p53).
Conclusions:
- 3-MeA adducts induced by Me-lex are not only cytotoxic but also exhibit premutagenic potential.
- The mutagenic activity of 3-MeA is strictly sequence-dependent, highlighting a novel aspect of DNA damage and repair.
- Me-lex provides a valuable tool for studying the sequence-specific mutagenic properties of 3-MeA lesions.