Comparison of the biological effects of MMS and Me-lex, a minor groove methylating agent: Clarifying the role of N3-methyladenine

作者：Monti Paola; Foggetti Giorgia; Menichini Paola; Inga Alberto; Gold Barry; Fronza Gilberto^*

来源：Mutation Research-Fundamental and Molecular Mechanisms of Mutagenesis, 2014, 759: 45-51.

DOI：10.1016/j.mrfmmm.2013.10.004

• MMS
• Me-lex
• 3-mA
• AP-site
• Yeast

N3-methyladenine (3-mA), generated by the reaction of methylating agents with DNA, is considered a highly toxic but weakly mutagenic lesion. However, due to its intrinsic instability, some of the biological effects of the adduct can result from the formation of the corresponding depurination product an apurinic (AP)-site]. Previously, we exploited Me-lex, i.e. {1-methyl-4-11methy1-4-(3-methoxysulfonylpropanamido)pyrrole-2-carboxamidol-Pyrrole-2 carboxamido}propane, a minor groove equilibrium binder with selectivity for A/T rich sequences that efficiently reacts with DNA to afford 3-mA as the dominant product, to probe the biology of this lesion. Using human p53 cDNA as a target in a yeast system, a weak increase in mutagenicity was observed in the absence of Magl (3methyladenine-DNA glycosylase 1, magl), the enzyme devoted to remove 3-mA from DNA. Moreover, a significant increase in mutagenicity occurred in the absence of the enzymes involved in the repair of APsites (AP endonucleases 1 and 2, apnl apn2). Since methyl methanesulfonate (MMS) has been extensively used to explore the biological effects of 3-mA, even though it produces 3-mA in low relative yield, we compared the toxicity and mutagenicity induced by MMS and Me-lex in yeast. A mutagenesis reporter plasmid was damaged in vitro by MMS and then transformed into wild-type and Translesion Synthesis (TLS) Polt (REV3) and Pohl (RAD30) deficient strains. Furthermore, a magl rad30 double mutant strain was constructed and transformed with the DNA plasmid damaged in vitro by Me-lex. The results confirm the important role of Pol in the mutagenic bypass of MMS and Me-lex induced lesions, with Pohl contributing only towards the bypass of Me-lex induced lesions, mainly in an error-free way. Previous and present results point towards the involvement of AP-sites, derived from the depurination of 3-mA, in the observed toxicity and mutagenicity.

• 出版日期2014-1