Nucleotide excision repair endonuclease genes in Drosophila melanogaster

Nucleotide excision repair (NER) is the primary pathway for the removal of ultraviolet light-induced damage and bulky adducts from DNA in eukaryotes. During NER, the helix is unwound around the damaged site, and incisions are made on the 5' and 3' sides, to release an oligonucleotide carrying the le sion. Repair synthesis can then proceed, using the intact strand as a templ ate. The incisions flanking the lesion are catalyzed by different structure -specific endonucleases. The 5' incision is made by a heterodimer of XPF an d ERCCl (Rad1p-Rad10p in Saccharomyces cerevisiae), and the 3' incision is made by XPG (Rad2p in S. cerevisiae). We previously showed that the Drosoph ila XPF homologue is encoded by the meiotic recombination gene mei-9. We re port here the identification of the genes encoding the XPG and ERCC1 homolo gues (XPG(Dm) and ERCC1(Dm)). XpG(Dm) is encoded by the mus201 gene; we fou nd frameshift mutations predicted to produce truncated XPG(Dm) proteins in each of two mus201 alleles. These mutations cause defects in nucleotide exc ision repair and hypersensitivity to alkylating agents and ultraviolet ligh t, but do not cause hypersensitivity to ionizing radiation and do not impai r viability or fertility. ERCC1Dm interacts strongly in a yeast two-hybrid assay with MEI-9, indicative of the presumed requirement for these polypept ides to dimerize to form the functional endonuclease. The Drosophila Ercc1 gene maps to polytene region 51D1-2. The nucleotide excision repair gene mu s210 maps nearby (51E-F) but is distinct from Ercc1. (C) 2000 Published by Elsevier Science B.V. All rights reserved.