Cyclic Labeling of Mammalian Cell DNA after X-Irradiation

Abstract

Summary

Starved L cells show a radiation-induced cyclic labeling of the acid-insoluble fraction when adenosine and deoxyadenosine are used as labeled precursors. The response consisted of a rapid uptake and loss of label. A similar effect has also been reported for ³²P labeling of DNA.

These findings support the idea that X-irradiation of mammalian cells produces increased action of an enzyme which rejoins single-strand breaks in DNA. The enzyme mechanism involves formation of a transient DNA-adenylate complex. In such a reaction, labeled adenylate should enter and then leave the DNA fraction. The results reported here agree with such a mechanism.