Reconstitution of 5'-directed human mismatch repair in a purified system

Cell. 2005 Sep 9;122(5):693-705. doi: 10.1016/j.cell.2005.06.027.


This paper reports reconstitution of 5'-nick-directed mismatch repair using purified human proteins. The reconstituted system includes MutSalpha or MutSbeta, MutLalpha, RPA, EXO1, HMGB1, PCNA, RFC, polymerase delta, and ligase I. In this system, MutSbeta plays a limited role in repair of base-base mismatches, but it processes insertion/deletion mispairs much more efficiently than MutSalpha, which efficiently corrects both types of heteroduplexes. MutLalpha reduces the processivity of EXO1 and terminates EXO1-catalyzed excision upon mismatch removal. In the absence of MutLalpha, mismatch-provoked excision by EXO1 occurs extensively. RPA and HMGB1 play similar but complementary roles in stimulating MutSalpha-activated, EXO1-catalyzed excision in the presence of a mismatch, but RPA has a distinct role in facilitating MutLalpha-mediated excision termination past mismatch. Evidence is provided that efficient repair of a single mismatch requires multiple molecules of MutSalpha-MutLalpha complex. These data suggest a model for human mismatch repair involving coordinated initiation and termination of mismatch-provoked excision.

Publication types

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

MeSH terms

  • 5' Flanking Region / physiology*
  • Base Pair Mismatch*
  • Cell-Free System / chemistry
  • Cell-Free System / metabolism
  • DNA Ligase ATP
  • DNA Ligases / metabolism
  • DNA Repair Enzymes / metabolism
  • DNA Repair*
  • DNA-Binding Proteins / metabolism*
  • Exodeoxyribonucleases / metabolism
  • HMGB1 Protein / metabolism
  • Humans
  • MutL Proteins
  • Neoplasm Proteins / metabolism
  • Replication Protein A


  • DNA-Binding Proteins
  • HMGB1 Protein
  • LIG1 protein, human
  • MutLalpha protein, human
  • Neoplasm Proteins
  • RPA1 protein, human
  • Replication Protein A
  • EXO1 protein, human
  • Exodeoxyribonucleases
  • MutL Proteins
  • DNA Ligases
  • DNA Repair Enzymes
  • DNA Ligase ATP