High frequency of genomic deletions induced by Me-lex, a sequence selective N3-adenine methylating agent, at the Hprt locus in Chinese hamster ovary cells

Debora Russo, Gilberto Fronza, Laura Ottaggio, Paola Monti, Alberto Inga, Prema Iyer, Barry Gold, Paola Menichini

Research output: Contribution to journalArticlepeer-review

Abstract

We have investigated the mutagenicity induced at the Hprt locus in Chinese hamster ovary (CHO) cells treated with increasing concentrations of Me-lex, a minor groove selective methylating agent that efficiently generates more than 90-95% of 3-MeA DNA adducts. Me-lex treatment was cytotoxic but weakly mutagenic, resulting in up to 7-fold induction above background in the Hprt mutation frequency. The molecular nature of 43 Hprt mutations induced by Me-lex was determined by sequence analysis of the Hprt cDNA and genomic analysis of the gene locus. Base pair substitutions represented about 25% of Me-lex induced mutations. The mutation spectrum revealed a high percentage of genomic deletions (51%) comprising single/multiple exon(s) and even the loss of the complete locus. When the distribution of mutations among different classes was considered, the difference between the spontaneous and Me-lex induced CHO spectra was statistically significant (p <0.012), indicating that the sites where mutations occurred were Me-lex specific. Based upon these results we hypothesize that a large proportion of mutations may result from the processing of 3-MeA, the main adduct induced by Me-lex, within A/T rich sequences in non-coding regions of the Hprt gene. The processing of these lesions by DNA polymerases could result in recombination and genomic deletions, thus representing a severe threat for genome integrity.

Original languageEnglish
Pages (from-to)58-66
Number of pages9
JournalMutation Research - Fundamental and Molecular Mechanisms of Mutagenesis
Volume671
Issue number1-2
DOIs
Publication statusPublished - Dec 1 2009

Keywords

  • Hamster cells
  • Hprt
  • Me-lex
  • Mutation induction

ASJC Scopus subject areas

  • Genetics
  • Molecular Biology
  • Health, Toxicology and Mutagenesis

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