EXCISION OF URACIL FROM BROMODEOXYURIDINE-SUBSTITUTED AND UV-IRRADIATED DNA IN CULTURED MOUSE LYMPHOMA-CELLS

A uracil-DNA glycosylase activity was detected in cell-free extracts from cultured mouse lymphoma L5178Y cells. We investigated whether or not this enzyme plays a role in the removal of uracil from chromosomal DNA. U.V. light (254 nm) irradiation of the cells with BUdR-substituted DNA produced not only single-strand breaks but also internal uracil residues that were recognized as substrate sites by uracil-DNA glycosylase. These internal uracil residues were lost from the DNA upon reincubation of the irradiated cells. The product released from the DNA was identified as uracil. Thus, the intracellular action of the uracil-DNA glycosylase was demonstrated and the subsequent reconstitution of the DNA strand was inferred in cultured mammalian cells. © 1979 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.