XPD helicase structures and activities: insights into the cancer and aging phenotypes from XPD mutations

Cell. 2008 May 30;133(5):789-800. doi: 10.1016/j.cell.2008.04.030.


Mutations in XPD helicase, required for nucleotide excision repair (NER) as part of the transcription/repair complex TFIIH, cause three distinct phenotypes: cancer-prone xeroderma pigmentosum (XP), or aging disorders Cockayne syndrome (CS), and trichothiodystrophy (TTD). To clarify molecular differences underlying these diseases, we determined crystal structures of the XPD catalytic core from Sulfolobus acidocaldarius and measured mutant enzyme activities. Substrate-binding grooves separate adjacent Rad51/RecA-like helicase domains (HD1, HD2) and an arch formed by 4FeS and Arch domains. XP mutations map along the HD1 ATP-binding edge and HD2 DNA-binding channel and impair helicase activity essential for NER. XP/CS mutations both impair helicase activity and likely affect HD2 functional movement. TTD mutants lose or retain helicase activity but map to sites in all four domains expected to cause framework defects impacting TFIIH integrity. These results provide a foundation for understanding disease consequences of mutations in XPD and related 4Fe-4S helicases including FancJ.

Publication types

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

MeSH terms

  • Archaeal Proteins / chemistry*
  • Archaeal Proteins / genetics*
  • Archaeal Proteins / metabolism
  • Cockayne Syndrome / genetics
  • Cockayne Syndrome / metabolism
  • Crystallography, X-Ray
  • DNA Helicases / chemistry
  • DNA Helicases / genetics
  • DNA Helicases / metabolism
  • DNA Repair
  • Iron-Sulfur Proteins / chemistry
  • Iron-Sulfur Proteins / genetics
  • Models, Molecular
  • Mutation
  • Protein Structure, Tertiary
  • Sequence Homology, Amino Acid
  • Structural Homology, Protein
  • Sulfolobus acidocaldarius / enzymology*
  • Trichothiodystrophy Syndromes / genetics
  • Trichothiodystrophy Syndromes / metabolism
  • Xeroderma Pigmentosum / genetics
  • Xeroderma Pigmentosum / metabolism
  • Xeroderma Pigmentosum Group D Protein / chemistry*
  • Xeroderma Pigmentosum Group D Protein / genetics*
  • Xeroderma Pigmentosum Group D Protein / metabolism


  • Archaeal Proteins
  • Iron-Sulfur Proteins
  • DNA Helicases
  • Xeroderma Pigmentosum Group D Protein

Associated data

  • PDB/3CRV
  • PDB/3CRW