Comparative study of nucleotide excision repair defects between XPD-mutated fibroblasts derived from trichothiodystrophy and xeroderma pigmentosum patients.

Abstract

To get a clue to understand how mutations in the XPD gene result in different skin cancer susceptibilities in patients with xeroderma pigmentosum (XP) or trichothiodystrophy (TTD), a thorough understanding of their nucleotide excision repair (NER) defects is essential. Here, we extensively characterize the possible causes of NER defects in XP-D and in TTD fibroblasts. The 3 XP-D cell strains examined were similarly deficient in repairing UV-induced cyclobutane pyrimidine dimers (CPDs) and (6-4) photoproducts (6-4PPs) from genomic DNA. The severity of NER defects correlated with their UV sensitivities. Possible alterations of TFIIH (which consists of 10 subunits including XPD) were then examined. All XP-D cell strains were normal in their concentrations of TFIIH, and displayed normal abilities to recruit TFIIH to sites of UV-induced DNA damage. However, replication protein A (RPA; single-stranded DNA binding protein) accumulation at DNA damage sites, which probably reflects the in vivo XPD helicase activity of TFIIH, is similarly impaired in all XP-D cell strains. Meanwhile, all 3 TTD cell strains had approximately 50% decreases in cellular TFIIH content. Importantly, 2 of the 3 TTD cell strains, which carry the major XPD mutations found in TTD patients, showed defective recruitment of TFIIH to DNA damage sites. Moreover, RPA accumulation at damage sites was impaired in all TTD cell strains to different degrees, which correlated with the severity of their NER defects. These results demonstrate that XP-D and TTD cells are both deficient in the repair of CPDs and 6-4PPs, but TTD cells have more multiple causes for their NER defects than do XP-D cells. Since TFIIH is a repair/transcription factor, TTD-specific alterations of TFIIH possibly result in transcriptional defects, which might be implication for the lack of increased incidence of skin cancers in TTD patients.

• Authors: Tomohisa Nishiwaki, Nobuhiko Kobayashi, Takaaki Iwamoto, Aya Yamamoto, Shigeki Sugiura, Yin-Chang Liu, Alain Sarasin, Yumiko Okahashi, Makito Hirano, Satoshi Ueno, Toshio Mori
• Journal: DNA repair (DNA Repair (Amst)) Vol. 7 Issue 12 Pg. 1990-8 (Dec 01 2008) ISSN: 1568-7864 [Print] Netherlands
• PMID: 18817897 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Pyrimidine Dimers
• RPA1 protein, human
• Replication Protein A
• Transcription Factor TFIIH
• Xeroderma Pigmentosum Group D Protein
• ERCC2 protein, human

Topics

• Cells, Cultured
• DNA Damage (radiation effects)
• DNA Repair
• Enzyme-Linked Immunosorbent Assay
• Fibroblasts (metabolism, radiation effects)
• Genome, Human
• Humans
• Pyrimidine Dimers (radiation effects)
• Radiation Tolerance
• Replication Protein A (genetics, metabolism)
• Transcription Factor TFIIH (genetics, metabolism)
• Trichothiodystrophy Syndromes (genetics)
• Ultraviolet Rays
• Xeroderma Pigmentosum (genetics)
• Xeroderma Pigmentosum Group D Protein (genetics)