A gene trap approach to isolate mammalian genes involved in the cellular response to genotoxic stress

Treatment of cells with DNA damaging agents leads to induction of a variety of genes involved in different cellular processes. We have applied a lacZ-based gene trap strategy to search for new mammalian genes induced by genotoxic stress. A population of 32 x 10(3) neo r clones stably transfected with a gene trap vector was obtained, stained with fluorescein di-beta-d-galactopyranoside and analyzed by flow activated cell sorting and replica plating. This strategy allowed isolation of 30 neo r 'putative inducible' cell lines expressing lacZ only after a DNA damaging treatment. For three clones the site of integration and the degree of inducibility after UV treatment were determined by Southern blot and beta-galactosidase measurement respectively. One cell line (clone VI) showed a single integration site and a reproducible 3-fold induction of beta-galactosidase activity following UV irradiation. Fused transcripts were isolated from induced cells and a portion of the trapped gene was amplified by rapid amplification of cDNA ends. Sequence analysis and comparison with available gene and protein databanks revealed that the gene was novel.