Resistance of the DNA strand in RNA-DNA hybrids to DNA repair

RNA-DNA hybrids are commonly observed during normal biological processes. We tested the ability of three DNA repair enzymes to remove lesions from the DNA strand of RNA-DNA heteroduplexes. Three nucleotide analogs, 8-oxo-dGTP, 5-OH-dCTP, and 06-methyl dGTP, representative of lesions generated by oxygen damage and methylating agents, were incorporated into the DNA strand synthesized using either a DNA or RNA template. The extended DNA-DNA and RNA-DNA hybrids were used as substrates for bacterial FaPyDNA glycosylase, endonuclease III and methyltransferase. We show that all three lesions are resistant to excision by DNA repair enzymes when present in the DNA strand of a RNA-DNA hybrid. In contrast, they are readily cleaved from the DNA strand of a DNA-DNA hybrid. Our in vitro studies suggest that damaged DNA in RNA-DNA hybrids present in cells is less likely to be repaired in vivo.