(A) Close-up views of the active site regions within the Polη 8-oxoG insertion (left) and postinsertion (right) complexes. The palm and fingers domains and the PAD are colored cyan, yellow, and green, respectively. The incoming dCTPs and the 8-oxoG lesions at the T0 position (left) and the T1 position (right) are shown in red. The DNA is colored gray, and the putative Mg2+ ions are dark blue. Highlighted are the catalytic residues (D30, D155, and E156), residues interacting with the incoming dCTP (F35, Y64, R67, and K279), residues interacting with the templating base (Q55) and the 5’ nucleotide (R73 and M74), and residues interacting with the phosphate group of the T1 nucleotide (W56, N398, and N400). (B) Hydrogen bonding interactions between Polη residues Q55, W56, N398, and N400 and the T0 and T1 nucleotides in the 8-oxoG insertion (left) and postinsertion (right) complexes. A water molecule (magenta) that mediates interaction between N400 and the O8 atom of 8-oxoG in the postinsertion complex is also shown (right).