Variations in DNA topoisomerase I activity after gamma irradiation of mature neurons.

ABSTRACT

The activity of DNA topoisomerase I in nuclear extracts from rat cerebral cortex neurons increases about two-fold after gamma irradiation (700 rads) of rats or incubated cerebral cortex slices. Analysis of the salt dependence of the DNA topoisomerase I association with chromatin shows a change of the activity only for tight-bound pool of the enzyme. The change appears to reflect a modification of the enzyme which results from its repair function.