Ataxia telangiectasia: an anomaly in DNA replication after irradiation

The effect of increasing dose of gamma-radiation on DNA synthesis in an ataxia telangiectasia lymphoblastoid cell line and a number of control lymphoblastoid cell lines was investigated. No significant inhibition of low molecular weight DNA synthesis was observed in the AT cell line at doses which resulted in considerable inhibition in the control cell lines. At higher doses, 600 to 800 rad, low molecular weight DNA synthesis and chain elongation were enhanced in the AT cell line. At time course study of DNA synthesis after 200 rads of gamma-radiation, revealed no appreciable inhibition of low and high molecular weight DNA synthesis up to 60 minutes postirradiation. However, in control cell lines, overall DNA synthesis was depressed to a level 50% of that shown by the unirradiated cells.