INEFFICIENT REPAIR OF RNA-CENTER-DOT-DNA HYBRIDS

RNA.DNA hybrids are commonly observed during normal biological process es. We tested the ability of three DNA-repair enzymes to remove lesion s from the DNA strand of RNA.DNA heteroduplexes. Three nucleotide anal ogs, 5-hydroxy-2'-deoxycytidine triphosphate, 8-oxo-2'-deoxyguanosine triphosphate, and O-6-methyl-2'-deoxyguanosine triphosphate, represent ative of lesions generated by oxygen damage and methylating agents, we re incorporated into the DNA strand synthesized using either a DNA or RNA template. The extended DNA.DNA and RNA.DNA hybrids were used as su bstrates for bacterial formamidopyrimidine-DNA glycosylase, Nth protei n (endonuclease III) and O-6-methylguanine-DNA methyltransferase. We s how that all three lesions are readily cleaved from the DNA strand of a DNA.DNA duplex but are relatively resistant to cleavage when present in the DNA strand of an RNA.DNA hybrid. Our in vitro studies suggest that damaged DNA in RNA.DNA hybrids is less likely to be repaired in v ivo.