Genetic evidence has implicated multiple pathways in eukaryotic DNA mismatch repair (MMR) downstream of mispair recognition and Mlh1-Pms1 recruitment, including Exonuclease 1 (Exo1)-dependent and -independent pathways. We identified 14mutations in POL30, which encodes PCNA in Saccharomyces cerevisiae, specific to Exo1-independent MMR. The mutations identified affected amino acids at three distinct sites on the PCNA structure. Multiple mutant PCNA proteins had defects either in trimerization and Msh2-Msh6 binding or inactivation of the Mlh1-Pms1 endonuclease that initiates excision during MMR. The latter class of mutations led to hyperaccumulation of repair intermediate Mlh1-Pms1 foci and were enhanced by an msh6 mutation that disrupted the Msh2-Msh6 interaction with PCNA. These results reveal a central role for PCNA in the Exo1-independent MMR pathway and suggest that Msh2-Msh6 localizes PCNA to repair sites after mispair recognition to activate the Mlh1-Pms1 endonuclease for initiating Exo1-dependent repair or for driving progressive excision in Exo1-independent repair.
|Number of pages||14|
|State||Published - Jul 17 2014|
Bibliographical noteFunding Information:
The authors thank Nikki Bowen for help with protein purification. This work is supported by NIH grants GM50006 and CA92584 (to R.D.K.), GM074215 (to A.D.) and CA23100 (to A.D. and R.D.K.), a NIH fellowship F32GM106598 (to E.M.G.), a Damon Runyon Cancer Research Foundation Fellowship (to C.S.C.), and the Harald zur Hausen Fellowship from the German Cancer Research Center, DKFZ (to H.H.).
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology