Trichothiodystrophy fibroblasts are deficient in the repair of ultraviolet-induced cyclobutane pyrimidine dimers and (6-4)photoproducts.
A photosensitive form of trichothiodystrophy (TTD) results from mutations in the same XPD gene as the DNA-repair-deficient genetic disorder xeroderma pigmentosum group D (XP-D). Nevertheless, unlike XP, no increase in skin cancers appears in patients with TTD. Although the ability to repair ultraviolet (UV)-induced DNA damage has been examined to explain their cancer-free phenotype, the information accumulated to date is contradictory. In this study, we determined the repair kinetics of cyclobutane pyrimidine dimers (CPD) and (6-4)photoproducts (6-4PP) in three TTD cell strains using an enzyme-linked immunosorbent assay. We found that all three TTD cell strains are deficient in the repair of CPD and of 6-4PP. UV sensitivity correlated well with the severity of repair defects. Moreover, accumulation of repair proteins (XPB and proliferating cell nuclear antigen) at localized DNA damage sites, detected using micropore UV irradiation combined with fluorescent antibody labeling, reflected their DNA repair activity. Importantly, mutations of the XPD gene affected both the recruitment of the TFIIH complex to DNA damage sites and the TFIIH expression. Our results suggest that there is no major difference in the repair defect between TTD and XP-D and that the cancer-free phenotype in TTD is unrelated to a DNA repair defect.
Radioisotope Research Center and Department of Dermatology, Nara Medical University, Kashihara, Nara, Japan.
Yoko
Y
Nishiwaki
Nobuhiko
N
Kobayashi
Kyoko
K
Imoto
Taka-aki
TA
Iwamoto
Aya
A
Yamamoto
Sachiko
S
Katsumi
Toshihiko
T
Shirai
Shigeki
S
Sugiura
Yu
Y
Nakamura
Alain
A
Sarasin
Sachiko
S
Miyagawa
Toshio
T
Mori
D004265:DNA Helicases; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics; D005347:Fibroblasts / Q000378:metabolism* / Q000528:radiation effects; D006201:Hair Diseases / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D006801:Humans; D066298:In Vitro Techniques; D008856:Microscopy, Fluorescence; D010777:Photochemistry; D011740:Pyrimidine Dimers / Q000378:metabolism*; D012720:Severity of Illness Index; D012867:Skin / Q000166:cytology; D014983:Xeroderma Pigmentosum / Q000235:genetics
D004268:DNA-Binding Proteins; D011740:Pyrimidine Dimers; C058406:pyrimidine-pyrimidone dimer; C072022:XPBC-ERCC-3 protein; D004265:DNA Helicases