Repair of a single CTG slip-out in a cell-free MMR assay is MLH1 dose-dependent.

(A) Short slipped-DNA repair using HeLa or HEK293T (MutLα-deficient) whole cell extracts complemented with equal amounts (100 ng) of purified MutLα protein complexes: hMLH1-hPMS2, mMLH1.B6-hPMS2 or mMLH1.129-hPMS2. Both B6 and 129 MLH1 proteins show ability to repair the mismatch when in a complex with hPMS2. The individual lanes represented are from the same blot. (B) Repair using MutLα-deficient HEK293T cell extracts complemented with increasing concentrations (5, 25 and 100 ng) of either mMLH1.B6-hPMS2 or mMLH1.129-hPMS2 protein complexes. Quantification of repair suggests that both B6 and 129 MLH1 proteins are comparably efficient at repairing CTG slip-outs. In addition, it suggests a MutLα dose-dependency, with higher concentrations of mMLH1-hPMS2 resulting in higher levels of MMR activity (p = 0.0013). The individual lanes represented are from the same blot and the experiment was reproduced three times. Bars graphs represent mean ±SD.