Mechanism of 5'-directed excision in human mismatch repair

Mol Cell. 2003 Nov;12(5):1077-86. doi: 10.1016/s1097-2765(03)00428-3.

Abstract

We have developed a purified system that supports mismatch-dependent 5'-->3' excision. In the presence of RPA, ATP, and a mismatch, MutSalpha activates 5'-->3' excision by EXOI, and excision terminates after removal of the mispair. MutSalpha confers high processivity on EXOI, and termination is due to RPA-dependent displacement of this processive complex from the helix and a weak ability of EXOI to reload at the RPA-bound gap in the product, as well as MutSalpha- and MutLalpha-dependent suppression of EXOI activity in the absence of a mismatch cofactor. As observed in the purified system, excision directed by a 5' strand break in HeLa nuclear extract can proceed in the absence of MutLalpha or PCNA, although 3' excision in the extract system requires both proteins.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphatases / metabolism
  • Adenosine Triphosphate / metabolism
  • Bacterial Proteins*
  • Base Pair Mismatch*
  • Cell Nucleus / chemistry
  • DNA / genetics
  • DNA / metabolism*
  • DNA Repair Enzymes
  • DNA Repair*
  • DNA-Binding Proteins / metabolism
  • Enzyme Activation
  • Escherichia coli Proteins / metabolism
  • Exodeoxyribonucleases / metabolism
  • HeLa Cells
  • Humans
  • MutL Proteins
  • MutS DNA Mismatch-Binding Protein
  • Replication Protein A

Substances

  • Bacterial Proteins
  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • MutL protein, E coli
  • RPA1 protein, human
  • Replication Protein A
  • Adenosine Triphosphate
  • DNA
  • EXO1 protein, human
  • Exodeoxyribonucleases
  • exodeoxyribonuclease I
  • Adenosine Triphosphatases
  • MutL Proteins
  • MutS DNA Mismatch-Binding Protein
  • MutS protein, E coli
  • DNA Repair Enzymes