RNA-DNA hybrids containing damaged DNA are substrates for RNase H

During the replication of the lagging strand, RNA-DNA hybrids are formed an d the RNA is subsequently degraded by the action of RNase H. Little is know n about the effects of damaged DNA on lagging strand replication and subseq uent RNA removal. The rates and sites of digestion by E. coli RNase H of RN A-DNA hybrids containing either a thymine glycol or urea site in the DNA st rand have been examined. The cleavage patterns for duplexes containing thym ine glycol or urea differ from that of a fully complementary duplex. There is one major product of the digestion of the fully complementary hybrid, bu t three products are formed in the reactions with the hybrids containing da maged DNAs. Cleavage is partially redirected to the position adjacent to th e damaged sites. The overall rate of cleavage of these hybrids containing d amaged DNA is comparable to that of the fully complementary duplex. These r esults indicate that the cleavage of RNA-DNA hybrids by RNase H is less sel ective when a damaged site is present in the DNA strand. (C) 2001 Elsevier Science Ltd. All rights reserved.