Figure 2.

RER model. A misincorporated ribonucleotide (green) is recognized by RNase H2 (blue), which cleaves on the 5′ side, leaving a nick. PCNA (blue ring) and DNA polymerase (Polϵ or Polδ) displace the strand with the ribonucleotide by replicating new DNA. A 5′ flap endonuclease (red) cuts, releasing the ribonucleotide-containing DNA strand. DNA ligase I seals the remaining nick, resulting in fully repaired DNA. The creation of the nick may signal strand discrimination or mating type switching, highlighting potential beneficial roles of rNTP incorporation.