NER in 165TOR cells. A and B, Comparative autoradiography of a mixed culture of normal C5RO (small cytoplasmic beads) and 165TOR patient fibroblasts (large beads). A, GG-NER was measured as UDS by pulse labeling the cells with ³H-thymidine after exposure to 16 J/m² UV-C, as described elsewhere.20 B, TC-NER was measured as RNA synthesis recovery (RSR) after UV by pulse labeling the cells with ³H-uridine 16 h after they were exposed to 16 J/m² UV. C, Quantification of UDS and RSR by counting the silver grains in 50 nuclei of 165TOR (black) compared with in normal cells on the same slide. Data are shown in comparison with XP-A, XP-C, and CS-B standard strains measured in separate experiments. D, Cell survival assay to measure UV sensitivity of 165TOR (dots) relative to that of normal (C5RO), XP-A (diamonds), XP-C (unblackened circles), and CS-B (crosses) standard strains. E and F, Immunofluorescence detection of NER proteins to sites of UV-induced DNA damage. 165TOR cells were exposed to local UV radiation as described elsewhere,27 were fixed after 1 h, and were stained with antibodies against TFIIH core component p62 and XPC (E) or with anti-XPA antibodies (F).

ERCC1/XPF protein levels in the patient and his parents. A and B, Comparative immunofluorescence with anti-ERCC1 (A) or anti-XPF (B) antibodies. Upper panels are mixed phase contrast and 4′-6 diamidino-2-phenylindole images, to demonstrate the presence of cytoplasmic beads in the normal control fibroblasts (C5RO), mixed 1:1 with 165TOR cells (which have no beads). Note cytoplasmic pseudofluorescence caused by the optic effects of beads. C–E, Immunoblots with anti-ERCC1 (C and E) or anti-XPF (D) on whole-cell extracts from C5RO (normal), two XP-F patient cell lines (XP42RO(F) and XP51RO(F)), 165TOR, and the mother and father of 165TOR. The relevant bands are indicated with arrows; cross-reacting bands (indicated by an asterisk [*]) served as loading controls. Note the presence of degraded ERCC1, specifically in 165TOR (C). F and G, Comparative immunodetection of ERCC1 on cells from the parents, compared with 165TOR and normal. Mixed cultures contained C5RO (large beads) and 165TOR cells.

Characteristics of patient 165TOR and Ercc1^−/− mice. A, Image of patient at birth. B, Arthrogryposis of hands and rocker-bottom feet and frontal face appearance. Note microcephaly. C and D, Nuclear magnetic resonance scans of head, demonstrating simplified gyral pattern and cerebellar hypoplasia. E, Hematoxylin-eosin stained sections of 1-d-old mice (top row) and 4-d-old mice (bottom row), demonstrating delayed development of Ercc1^−/− mouse cerebellum (including hypoplasia and blunted gyri) compared with that of wild-type (WT) littermates. Images are representative of those obtained for at least three mice of each genotype.

ERCC1 defect in patient 165TOR. A and B, UV-induced UDS measured after microinjection of purified ERCC1-XPF protein complex (A) or ERCC1-GFP expression vector (B) into 165TOR multikaryons (arrows). Note the low number of grains in single cells from the same patient that were not injected. C and D, Partial genomic sequences of ERCC1 exon 5 (Q¹⁵⁸X) and exon 7 (F²³¹L). The presence of Q¹⁵⁸X was verified by restriction analysis of the destroyed PstI site (boxed). E, Schematic diagram of ERCC1, indicating exons (Roman numerals), known protein domains (XPA and XPF binding domain [BD] and helix-hairpin-helix [HLH] DNA binding motifs), and the inactivating mutations found in patient 165TOR (red-shaded boxes). The mutation identified in 43-3B CHO cells, which have undetectable levels of ERCC1-XPF, is also indicated (blue-shaded box). F and G, Fusion of mouse Ercc1^−/− embryonic fibroblasts with human fibroblasts (165TOR [F] and XPB [G]), followed by UDS assay. Note noncomplementation in panel E and complementation in panel G. Heterokaryons were identified on the basis of cytoplasmic beads as well as by nucleolar morphology.

Functionality of mutant ERCC1 cDNA. A, Clonogenic survival assay to measure sensitivity of fibroblasts to the crosslinking agent mitomycin C. 165TOR cells are compared with normal primary and human tert-immortalized fibroblasts (C5RO(tert)). For panels B–E, ERCC1-deficient 43-3B cells were stably transfected with expression plasmids carrying human ERCC1 or human ERCC1-GFP driven by a cytomegalovirus promoter and a neo^R selection marker. G⁴¹⁸-resistant mass populations were checked for survival after exposure to UV (C) or mitomycin C (D), compared with untransfected 43-3B cells (blackened squares) and wild-type AA8 cells (unblackened squares). Vectors were ERCC1 wild type (WT) (diamonds), ERCC1 F²³¹L (triangles), and ERCC1 Q¹⁵⁸X (circles). Blackened and unblackened symbols represent ERCC1 and ERCC1-GFP constructs, respectively. B and E, Western blots of transfected mass populations by use of antibodies against XPF (B) or ERCC1 (E). Cross-reacting bands (serving as loading controls) are indicated by an asterisk (*).