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

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• 作者：Paola Monti ; Giorgia Foggetti ; Paola Menichini ; Alberto Inga ; Barry Gold ; Gilberto Fronza
• 关键词：AP ; apurinic/apyrimidinic ; apn1apn2 ; AP endonucleases 1 and 2 defective ; BER ; base excision repair ; 3-mA ; N3-methyladenine ; 3-m-c3A ; 3-methyl-3-deazaadenine ; mag1 ; 3-methyladenine-DNA glycosylase 1 defective ; Me-lex ; {1-methyl-4-[1-methyl-4-(3-methoxysulfonylpropanamido)pyrrole-2-carboxamido]-pyrrole-2-carboxamido}propane ; MF ; mutation frequency ; MMS ; methyl methanesulfonate ; TLS ; Translesion Synthesis ; sMF ; spontaneous mutation frequency
• 刊名：Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
• 出版年：January, 2014
• 年：2014
• 卷：759
• 期：Complete
• 页码：45-51
• 全文大小：772 K

文摘

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-[1-methyl-4-(3-methoxysulfonylpropanamido)pyrrole-2-carboxamido]-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 Mag1 (3-methyladenine-DNA glycosylase 1, mag1), 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 AP-sites (AP endonucleases 1 and 2, apn1apn2). 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) Pol味 (REV3) and Pol畏 (RAD30) deficient strains. Furthermore, a mag1rad30 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味 in the mutagenic bypass of MMS and Me-lex induced lesions, with Pol畏 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.