XRCC1 deficiency influences the cytotoxicity and the genomic instability induced by Me-lex, a specific inducer of N3-methyladenine.

Abstract

Me-lex is a sequence-specific alkylating agent synthesized to preferentially (>90%) generate N3-methyladenine (3-mA) in the minor groove of double-strand DNA, in A-T rich regions. In this paper we investigated the effect of XRCC1 deficiency in the processing of 3-mA adducts generated by Me-lex, through the molecular analysis of the Hprt mutations and the evaluation of cytogenetic end points such as sister chromatid exchanges (SCEs), micronuclei (MN) and nucleus fragmentation. EM-C11 cells, deficient in XRCC1 activity, showed a 2.5-fold higher sensitivity to the toxicity of Me-lex compared to the DNA repair proficient parental CHO-9 cells, but were not hyper mutable. The spontaneous mutation spectrum at the Hprt locus generated in EM-C11 cells revealed a high percentage of genomic deletions. After Me-lex treatment, the percentage of genomic deletions did not increase, but a class of mutations which appeared to target regulatory regions of the gene significantly increased (p=0.0277), suggesting that non-coding Hprt genomic sequences represent a strong target for the rare mutations induced by Me-lex. The number of SCEs per chromosome increased 3-fold above background in 50mucapital EM, Cyrillic Me-lex treated CHO-9 cells, while at higher Me-lex concentrations a sharp increase in the percentage of MN and fragmented nuclei was observed. In EM-C11 cells the background level of SCEs (0.939+/-0.182) was approximately 10-fold higher than in CHO-9 (0.129+/-0.027) and higher levels of multinucleated cells and MN were also found. In EM-C11, even low doses of Me-lex (25microM) led to a significant increase in genomic damage. These results indicate that XRCC1 deficiency can lead to genomic instability even in the absence of an exogenous genotoxic insult and low levels of Me-lex-induced lesions, i.e., 3-mA and/or a BER intermediate, can exacerbate this instability.

• Authors: Debora Russo, Gilberto Fronza, Laura Ottaggio, Paola Monti, Chiara Perfumo, Alberto Inga, Prema Iyer, Barry Gold, Paola Menichini
• Journal: DNA repair (DNA Repair (Amst)) Vol. 9 Issue 7 Pg. 728-36 (Jul 01 2010) ISSN: 1568-7856 [Electronic] Netherlands
• PMID: 20471330 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: 2010 Elsevier B.V. All rights reserved.

Chemical References

• Alkylating Agents
• DNA-Binding Proteins
• Mutagens
• X-ray Repair Cross Complementing Protein 1
• methyl lexitropsin
• 3-methyladenine
• Netropsin
• Adenine

Topics

• Adenine (analogs & derivatives, metabolism)
• Alkylating Agents (pharmacology)
• Animals
• CHO Cells
• Cricetinae
• Cricetulus
• DNA Damage (genetics)
• DNA-Binding Proteins (genetics)
• Genomic Instability (genetics)
• Mutagens (pharmacology)
• Netropsin (analogs & derivatives, pharmacology)
• Sequence Deletion
• X-ray Repair Cross Complementing Protein 1