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Journal of Nucleic Acids
Volume 2010 (2010), Article ID 426505, 14 pages
http://dx.doi.org/10.4061/2010/426505
Research Article

Effect of N3-Methyladenine and an Isosteric Stable Analogue on DNA Polymerization

1Eppley Institute for Research in Cancer, University of Nebraska Medical Center, Omaha, NE 68198-6805, USA
2Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, NE 68198-6805, USA
3Department of Pharmaceutical Sciences, University of Pittsburgh, Pittsburgh, PA 15261, USA
4Molecular Mutagenesis and DNA Repair Unit, Department of Epidemiology and Prevention, National Cancer Research Institute (IST), 16132 Genova, Italy

Received 29 January 2010; Accepted 25 June 2010

Academic Editor: Ramón Eritja

Copyright © 2010 Samuel Settles et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

N3-methyladenine (3-mA) is a cytotoxic lesion formed by the reaction of DNA with many methylating agents, including antineoplastic drugs, environmental agents and endogenously generated compounds. The toxicity of 3-mA has been attributed to its ability to block DNA polymerization. Using Me-lex, a compound that selectively and efficiently reacts with DNA to afford 3-mA, we have observed in yeast a mutational hotspot at the -terminus of an A4 tract. In order to explore the potential role of sequence-dependent DNA polymerase bypass of 3-mA, we developed an in vitro system to prepare 3-mA modified substrates using Me-lex. We detail the effects of 3-mA, its stable isostere analogue, 3-methyl-3-deazaadenine, 3-deazaadenine and an THF abasic site on DNA polymerization within an A4 sequence. The methyl group on 3-mA and 3-methyl-3-deazaadenine has a pronounced inhibitory effect on DNA polymerization. There was no sequence selectivity for the bypass of any of the lesions, except for the abasic site, which was most efficiently by-passed when it was on the -terminus of the A4 tract. The results indicate that the weak mutational pattern induced by Me-lex may result form the depurination of 3-mA to an abasic site that is bypassed in a sequence dependent context.