PCNA and Msh2-Msh6 activate an Mlh1-Pms1 endonuclease pathway required for Exo1-independent mismatch repair

Mol Cell. 2014 Jul 17;55(2):291-304. doi: 10.1016/j.molcel.2014.04.034. Epub 2014 Jun 26.


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 14 mutations 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 in activation 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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism*
  • Carrier Proteins / metabolism*
  • DNA Mismatch Repair
  • DNA, Fungal / genetics
  • DNA-Binding Proteins / metabolism*
  • Enzyme Activation
  • Exodeoxyribonucleases / metabolism*
  • Models, Molecular
  • MutL Protein Homolog 1
  • MutL Proteins
  • MutS Homolog 2 Protein / metabolism*
  • Mutation, Missense
  • Proliferating Cell Nuclear Antigen / chemistry
  • Proliferating Cell Nuclear Antigen / genetics*
  • Proliferating Cell Nuclear Antigen / metabolism
  • Protein Binding
  • Protein Interaction Domains and Motifs
  • Protein Multimerization
  • Protein Stability
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / genetics*
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Signal Transduction


  • Adaptor Proteins, Signal Transducing
  • Carrier Proteins
  • DNA, Fungal
  • DNA-Binding Proteins
  • MLH1 protein, S cerevisiae
  • MSH6 protein, S cerevisiae
  • PMS1 protein, S cerevisiae
  • POL30 protein, S cerevisiae
  • Proliferating Cell Nuclear Antigen
  • Saccharomyces cerevisiae Proteins
  • Exodeoxyribonucleases
  • exodeoxyribonuclease I
  • MSH2 protein, S cerevisiae
  • MutL Protein Homolog 1
  • MutL Proteins
  • MutS Homolog 2 Protein