Suppression of UV-induced apoptosis by the human DNA repair protein XPG

Cell Death Differ. 2006 Mar;13(3):478-88. doi: 10.1038/sj.cdd.4401764.

Abstract

The severe xeroderma pigmentosum/Cockayne syndrome (XP/CS) syndrome is caused by mutations in the XPB, XPD and XPG genes that encode the helicase subunits of TFIIH and the 3' endonuclease of nucleotide excision repair (NER). Because XPB and XPD have been implicated in p53-mediated apoptosis, we examined the possible involvement of XPG in this process. After ultraviolet light (UV) irradiation, primary fibroblasts of XP complementation group G (XP-G) individuals with CS enter apoptosis more readily than other NER-deficient cells, but this is unlinked to unrepaired damage. These XP-G/CS cells accumulate p53 post-UV but they fail to accumulate the 90/92 kDa isoforms of Mdm2 and their cellular distribution of Mdm2 is impaired. Apoptosis levels revert to wild type, Mdm2 90/92 kDa isoforms accumulate, and Mdm2 regains its normal post-UV nuclear location in transduced XP-G/CS cells expressing wild-type XPG, but not an XPG catalytic site mutant. These results suggest that XPG suppresses UV-induced apoptosis and that this suppression, most simply, requires its endonuclease function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis*
  • Cell Nucleus / chemistry
  • Cells, Cultured
  • DNA Damage
  • DNA Repair
  • DNA-Binding Proteins / deficiency
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / physiology*
  • Endonucleases / deficiency
  • Endonucleases / genetics
  • Endonucleases / physiology*
  • Fibroblasts / metabolism
  • Fibroblasts / radiation effects
  • Genetic Vectors
  • Humans
  • Lentivirus / genetics
  • Mutation
  • Nuclear Proteins / deficiency
  • Nuclear Proteins / genetics
  • Nuclear Proteins / physiology*
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Proto-Oncogene Proteins c-mdm2 / analysis
  • Proto-Oncogene Proteins c-mdm2 / genetics
  • Proto-Oncogene Proteins c-mdm2 / metabolism
  • RNA, Messenger / metabolism
  • Transcription Factors / deficiency
  • Transcription Factors / genetics
  • Transcription Factors / physiology*
  • Tumor Suppressor Protein p53 / metabolism
  • Ultraviolet Rays*
  • Xeroderma Pigmentosum / genetics

Substances

  • DNA excision repair protein ERCC-5
  • DNA-Binding Proteins
  • Nuclear Proteins
  • Protein Isoforms
  • RNA, Messenger
  • Transcription Factors
  • Tumor Suppressor Protein p53
  • Proto-Oncogene Proteins c-mdm2
  • Endonucleases