Phenotype of FAECB (Facility for Automated Experiments in Cell Biology) Chinese hamster ovary mutants with minimal UV-sensitivity

The Facility for Automated Experiments in Cell Biology (FAECB) collection o f over 200 lines of ultraviolet (UV)-sensitive mutant Chinese hamster ovary (CHO) cells has previously been studied for complementation group assignme nt (CG), with representatives of rodent UV CGs 1-6 (ERCC1-6) and the new ro dent XRCC9/FANCG group identified. Ten mutants from the collection, includi ng a further six derived from wildtype AA8, three UV-sensitive double-mutan ts of CHO ERCC1 cell line UV4, and a UV-sensitive mutant of CHO XRCC1 cell line EM9, had not been assigned or characterized in these previous studies. These 10 mutants include 8 with approximately 1.5-fold the UV-sensitivity of the parental line (AAS, EM9, or UV4), and 2 with about 2-fold the UV-sen sitivity of AAS. The present study reports the partial characterization of these 10 mutants in terms of sensitivity to UV (with and without caffeine), ionizing radiation, mitomycin C (MMC) and ethyl methanesulfonate (EMS); pr oficiency in DNA repair (unscheduled DNA synthesis (UDS)); and UV-mutabilit y. The phenotypes of the 10 cell lines were heterogeneous, a number showed reduced UDS or UV-sensitization by caffeine, whilst others showed marked se nsitivity to EMS or MMC, and they may have mutations in different genes inv olved in nucleotide excision repair, post-replicational repair, base excisi on repair or recombinational repair. Previous mutants isolated as part of t he FAECB collection have proved to be extremely important in characterizing mammalian DNA repair processes and cloning human repair genes and these cu rrent mutants, whilst not as hypersensitive to UV, may still have the poten tial to make further contributions. (C) 2001 Elsevier Science B.V. All righ ts reserved.