EFFECT OF X IRRADIATION ON THE PRIMING ACTIVITY OF DNA

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Abstract
The activity of DNA as a primer for RNA-and DNA-polymerase from E. coli was severely depressed by X-irradiation in doses of 1,000 r or less. The priming activity for DNA -polymerase was more readily affected and was reduced in the case of DNA extracted from irradiated lymphoblasts, as well as for DNA irradiated in dilute solution. The optimum concentration of primer in the DNA-polymerase reaction was lower for irradiated DNA than for control DNA; concentrations higher than the optimum being inhibitory in both cases. Mixtures of irradiated and control DNA showed a lower priming activity than that of control DNA alone, the extent of the decrease depending on the ratio of the concentration of the control to the irradiated DNA in the mixture, as well as on the amount of enzyme present. The nature of irradiation damage to DNA which is responsible for the reduced priming activity remains to be determined.