Figure 1.

Msh2/Msh6-dependent suppression of UVC-induced mutations is not related to ncMMR. (A) C’s within CPD lesions can deaminate spontaneously to U’s that instruct the mutagenic incorporation of adenines during replication. Excision of U-containing CPD by ncMMR might preclude their mutagenicity. Levels of site-specific UU-CPD at an ectopic Hprt minigene can be quantified, after photoreversal of the CPD in vitro, by PCR using primers with a 3′ AA dinucleotide and quantitative Southern blotting. Primers with a 3′ GG dinucleotide are used as standards (see Hendriks et al., 2010 for primer sequences). (B) Autoradiographs of Southern blots of PCR products, specific for the four tested UU-CPD. Numerals refer to the position in the Hprt cDNA. TS, UU-CPD at the transcribed strand; NTS, UU-CPD at the nontranscribed strand; X, Xpa^−/−; MX, Msh6^−/−Xpa^−/−. (C) Quantification of deaminated CC-CPD from the autoradiographs shown in B, corrected for the standards.