The excision repair of UV-induced pyrimidine dimers was investigated in three genes: Gart, Notch and white in a permanent Drosophila cell line Kc, derived from wild type Drosophila melanogaster embryonic cells. In this cell line Gart and Notch are actively transcribed, whereas white is not expressed. In all three genes UV-induced pyrimidine dimers were removed with the same rate and to the same extent: 60% removal within 16 hours, up to 80-100% in 24 hours after irradiation with 10 or 15 J/m2 UV. These kinetics are similar to the time course of dimer removal measured in the genome overall. No difference in repair of the inactive white locus compared to the active Gart and Notch genes was found. Similar results were obtained using a different wild type cell line, SL2, although repair appeared to be somewhat slower in this cell line. The results are discussed with respect to the data found for gene specific repair in other eukaryotic systems.
The nucleotide excision repair (NER; dark-repair) of (6-4)photoproducts ((6-4)PPs) was assayed in cells from a permanent Drosophila melanogaster embryonic cell line, Kc, after exposure to 20 or 40 J/m2 ultraviolet (UV) light. Induction rates in the transcriptionally active genes Gart and Notch as well as in the inactive white locus is similar. They are formed with a frequency of about one-third of that of cyclobutane pyrimidine dimers (CPDs). In all three genes, (6-4)PPs are repaired with the same rate and to the same extent: 31% of the (6-4)PPs are removed in 4 hours post-irradiation and after 16 hours repair is nearly complete. In none of the three genes strand-specific repair was found. Exposure of cells that were irradiated with 40 J/m2 UV to photoreactivating light for 1 hour prior to dark-repair incubation, resulted in enhanced repair of (6-4)PPs.
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