Fig. 7.

Mechanism by which specialized polymerases contribute to NHEJ. (A) Diverse end structures relevant to synthesis during NHEJ may be addressed by these polymerases similarly, as if alignments always generate one-nucleotide gaps, by adjusting template (grayed positions) upstream (Pol μ) or down stream (Pol λ) of the nascent base pair (red) when gaps are longer than one nucleotide. (B) Complex DSBs are ligated after synthesis by a Pol X polymerase on its cognate substrate or after nuclease activity remodels the initial end structure to a cognate substrate for the other polymerase. In the absence of polymerase activity ligation is more reliant on microhomologies, likely uncovered by repeated cycles of nuclease activity, and is associated with increased deletion.