CHARACTERIZATION OF SPONTANEOUS AND INDUCED MUTATIONS IN SV40-TRANSFORMED NORMAL AND ATAXIA-TELANGIECTASIA CELL-LINES

Spontaneous and induced mutations at the HPRT locus were analyzed in o ne normal (MRC5CV1) and one ataxia telangiectasia (AT5BIVA) SV40-trans formed cell line derived from male donors. Multiplex PCR and Southern analyses revealed a high frequency of spontaneous deletion mutations t hat may be a consequence of the SV40 transformation. Four mutagens (et hyl methanesulfonate, bromodeoxyuridine, bleomycin, adriamycin), which differ in their types of primary DNA lesions, caused specific pattern s of mutations. By using fluorescence in situ hybridization (FISH) tec hniques, we were able to show that more than 90% of the AT5BIVA cells contained two X chromosomes with HPRT alleles, while in more than 90% of the MRC5CV1 cells genomic hemizygosity for the HPRT gene was found. Taking into account these findings we found that the AT5BIVA cell lin e possesses spontaneous hypermutability as well as hypersensitivity an d hypermutability to bleomycin (BLM) and adriamycin (AM). Both mutagen s induced deletion mutations in both cell lines but more complex mutat ions and larger deletions were found in AT5BIVA cells.