X-RAY-INDUCED TRANSCRIPTIONAL ACTIVATION OF C-MYC AND XRCC1 GENES IN ATAXIA-TELANGIECTASIA CELLS

The transcriptional level of c-myc, c-jun and XRCC1 genes after X-irra diation was compared in human cells originating from subjects presumab ly with different DNA repair abilities. The mRNA amount of the beta-ac tin gene was used as an internal standard of transcription. The relati ve mRNA level of c-myc and XRCC1 genes was significantly increased 15 min after X-irradiation with doses of 2-8 Gy in ataxia telangiectasia (AT) cells (AT5BIVA and TAT2SF), in contrast to little change in xerod erma pigmentosum (XP2OS(SV) and XF2YO(SV)) and normal cells (WI38VA13 and GM0637). The increased mRNA level of the XRCC1 gene in AT5BIVA and of the c-myc and XRCC1 genes in TAT2SF cells was maintained for up to 8 h after X-irradiation with 2 Gy. For the c-jun mRNA level after X-i rradiation with 2-8 Gy, no significant change was observed in all cell lines tested. These results indicate that AT cells show a high transc riptional response of certain genes in response to X-irradiation, and suggest that the transcriptional activation of c-myc and XRCC1 genes a fter X-irradiation may be related to the hyper-radiosensitivity of AT cells.