HIGH-LEVEL EXPRESSION OF THE PHOTOREPAIR GENE IN DROSOPHILA OVARY ANDITS EVOLUTIONARY IMPLICATIONS

DNA photolyase catalyzes light-dependent repair of cis,syn-cyclobutane dipyrimidines (pyrimidine dimers); its apoenzyme is encoded by the ph otorepair (phr) gene. The phr cDNA was cloned from D. melanogaster; it has an open reading frame to encode a 61483-Da protein. The phr cDNA hybridized to band 44C-D of Drosophila polytene chromosome, equivalent to the locus of the phr(-) gene. Drosophila photolyase is made of an apoenzyme with a molecular weight of 62 kDa. Drosophila photolyase is extraordinarily abundant in the embryo and adult ovary, whereas mRNA o f the phr gene is abundant only in the ovary. The action spectrum of D rosophila photolyase for photoreactivation has a maximum at 440 nm. Th e phr gene of Drosophila has about 60% identical amino acid sites with that of goldfish but only 13-18% with those of microorganisms. Implic ations of the unique characteristics of the Drosophila phr gene are di scussed overviewing the diversified characteristics of phr genes in va rious organisms that have presumably evolved from a common ancestral g ene.