The cytochrome P450 geneCyp6a2fromDrosophila melanogasteris located on the right arm of chromosome 2 at position 43A1-2 and comprises two exons separated by a 69-bp intron. Phenobarbital treatment of flies leads to a rapid increase in the level of CYP6A2 mRNA and to an increased production of the CYP6A2 protein. DNA from theCyp6a2promoter region was functional when linked to a luciferase reporter gene and transfected intoD. melanogasterSchneider cells. Moreover, a dose-dependent induction of luciferase activity by phenobarbital indicated that elements necessary for phenobarbital induction are located within 428 bp of the translation start site. Heterologous expression of the CYP6A2 protein in lepidopteran cells infected with aCyp6a2-recombinant baculovirus was observed by Western blotting of cell lysates and by spectral characterization of the reduced-CO complex of the P450. The CYP6A2 protein produced in this system metabolized aldrin and heptachlor to their epoxides and metabolized the insecticide diazinon by desulfuration to diazoxon and by oxidative ester cleavage to 2-isopropyl-4-methyl-6-hydroxypyrimidine. Metabolism in lysates of cells infected with recombinant baculovirus was greatly enhanced by the addition of purified housefly NADPH cytochrome P450 reductase and cytochromeb5. These results show that CYP6A2 catalyzes the metabolism of organophosphorus insecticides and they implicateCyp6a2overexpression in metabolic resistance. TheCyp6a2gene appears to be a suitable model for a genetic analysis of the phenobarbital induction process.
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