Molecular cloning of the acr-2 gene which controls acriflavine sensitivity in Neurospora crassa.

The acr-2 gene of Neurospora crassa was cloned by complementation of the wild-type strain by DNA from an acriflavine-resistant strain, acr-2. The transcript of the acr-2 gene is 2.3 kb long and contains two leader open reading frames (ORFs) that precede the acr-2 coding region and, if translated, they would generate sequences of 23 and 43 amino acid residues, respectively. The predicted ACR-2 protein contains 595 amino acids that include a putative Zn(II)Cys6 binuclear domain that is followed by a rather long serine/threonine-rich region near the amino-terminus. The acr-2 mutation, which confers acriflavine resistance, substitutes the amino acid residue at position 303 of the encoded protein from asparagine to lysine. Progeny that were hypersensitive to acriflavine were obtained by disruption of the acr-2 gene by repeat induced point mutation (RIP). The level of expression of the acr-2 gene is significantly higher in the acr-2 strain than in the wild-type strain. These results indicate that the acr-2 gene controls acriflavine sensitivity in N. crassa.