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Methanol and acriflavine resistance in Dictyostelium are caused by loss of catalase

Division of Biological Sciences, University of Missouri, Columbia, MO 65211-7400, USA¹
School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK²
Laboratory for Molecular Cell Biology, UCL, Gower Street, London WC1E 6BT, UK³

Author for correspondence: Robert H. Insall. Tel: +44 121 414 2507. Fax: +44 121 414 3982. e-mail: r.h.insall{at}bham.ac.uk

Various chemicals with harmful effects are not themselves toxic, but are metabolized in vivo to produce toxic products. One example is methanol in Dictyostelium, which is lethal to cells containing the acrA gene, but relatively harmless to acrA mutants. This makes methanol resistance one of the tightest genetic selections in Dictyostelium. Loss of acrA also confers cross-resistance to unrelated compounds such as acriflavine and thiabendazole. We have used insertional mutagenesis to demonstrate that the acrA locus encodes the peroxisomal catalase A enzyme. Disruption of the catA gene results in parallel resistance to acriflavine. Molecular and biochemical studies of several previously characterized methanol-resistant strains reveal that each lacks catalase activity. One allele, acrA2, contains a 13 bp deletion which introduces a frameshift in the middle of the gene. The involvement of catalase in methanol resistance in Dictyostelium compares with its role in methanol metabolism in yeast and rodents. However, this is the first study to show that catalase is required for the toxicity of acriflavine. Our results imply that acriflavine and thiabendazole are precursors which must be oxidized to generate biologically active species. The catA/acrA gene is also a potentially invaluable negative selectable marker for Dictyostelium molecular genetics.

Keywords: alcohol metabolism, methanol, xenobiotics, prodrug, isoniazid

Abbreviations: REMI, restriction enzyme mediated integration

The GenBank accession number for the sequence reported in this paper is AF090443.

^a Ma. X. U. Garcia and C. Roberts contributed equally to this work.