Figure 4.

A scheme presenting the repair of mismatched nucleotides by MMR based on a mammalian model. A mismatched pair of nucleotides at complementary DNA strands does not create correct hydrogen bonds (a). The MutSα complex, composed of MSH2 and MSH6 recognizes unpaired bases (b). MutSα interacts with MutLα made up of MLH1 and PMS2. The MutSα-MutLα-DNA complex interacts with PCNA (c). PCNA activates MutLα attenuated endonuclease activity, which cleaves the DNA strand (d). 5′-3′ exonuclease of activity of EXO1, activated by MutSα or MutLα bound to the lesion, removes the DNA fragment containing incorrect nucleotide (e). Resynthesis of a missing DNA strand performed by pol δ or pol ε and assisted by PCNA is followed by its ligation performed by LIG1 (f).