Site-directed mutagenesis analysis of the structural interaction of the single-strand-break repair protein, X-ray cross-complementing group 1, with DNA polymerase beta

Nucleic Acids Res. 2003 Jan 15;31(2):580-8. doi: 10.1093/nar/gkg159.


Human X-ray cross-complementing group 1 (XRCC1) is a single-strand DNA break repair protein which forms a base excision repair (BER) complex with DNA polymerase beta (beta-Pol). Here we report a site- directed mutational analysis in which 16 mutated versions of the XRCC1 N-terminal domain (XRCC1-NTD) were constructed on the basis of previous NMR results that had implicated the proximity of various surface residues to beta-Pol. Mutant proteins defective in XRCC1-NTD interaction with beta-Pol and with a beta-Pol-gapped DNA complex were determined by gel filtration chromatography and a gel mobility shift assay. The interaction surface determined from the mutated residues was found to encompass beta-strand D and E of the five-stranded beta-sheet (betaABGDE) and the protruding alpha2 helix of the XRCC1-NTD. Mutations that included F67A (betaD), E69K (betaD), V86R (betaE) on the five-stranded beta-sheet and deletion of the alpha2 helix, but not mutations within alpha2, abolished binding of the XRCC1-NTD to beta-Pol. A Y136A mutant abolished beta-Pol binding, and a R109S mutant reduced beta-Pol binding. E98K, E98A, N104A, Y136A, R109S, K129E, F142A, R31A/K32A/R34A and delta-helix-2 mutants displayed temperature dependent solubility. These findings confirm the importance of the alpha2 helix and the betaD and betaE strands of XRCC1-NTD to the energetics of beta-Pol binding. Establishing the direct contacts in the beta-Pol XRCC1 complex is a critical step in understanding how XRCC1 fulfills its numerous functions in DNA BER.

Publication types

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

MeSH terms

  • Amino Acid Substitution
  • Binding Sites / genetics
  • Chromatography, High Pressure Liquid
  • DNA Polymerase beta / metabolism*
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Electrophoresis, Polyacrylamide Gel
  • Magnetic Resonance Spectroscopy
  • Mutagenesis, Site-Directed
  • Mutation
  • Protein Binding
  • Protein Conformation
  • Protein Folding
  • Solubility
  • Temperature
  • X-ray Repair Cross Complementing Protein 1


  • DNA-Binding Proteins
  • X-ray Repair Cross Complementing Protein 1
  • XRCC1 protein, human
  • DNA Polymerase beta