Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0043346 (xeroderma pigmentosum)
 2,924 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Xeroderma pigmentosum (XP), Cockayne syndrome (CS) and trichothiodystrophy (TTD) are genetic disorders with very different clinical features, but all associated with defects in nucleotide excision repair. Defects in the XPA or XPC genes confer sensitivity to UV carcinogenesis in both humans and mice, but only XPA(-/-) mice have increased acute responses to UV exposure, whereas XPC(-/-) mice are normal in this respect. Both XPE and XPF proteins have functions separate from their role in NER, but the exact nature of these functions has not yet been established. The CSA and CSB genes responsible for CS are both components of complexes associated with RNA polymerase II and their role is thought to be in assisting polII in dealing with transcription blocks. XPB and XPD proteins are components of transcription factor TFIIH, which is involved in both basal and activated transcription. XPB is part of the core of TFIIH and has a central role in transcription, whereas XPD connects the core to the CAK subcomplex, and can tolerate many different mutations. Subtle differences in the effects of these different mutations on the many activities of TFIIH and on its stability determine the clinical outcomes, which can be XP, TTD, XP with CS, XP with TTD or COFS. Features of single and double mutant mice indicate that the neurological and ageing features associated with these disorders result from the defects in NER in association with the transcriptional deficiencies. Skin tumours in XP patients have mutations characteristic of UV-induction in the ras, p53 and ptch genes, showing that sunlight-induced mutations in these genes are important in carcinogenesis in XP patients.
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PMID:DNA repair-deficient diseases, xeroderma pigmentosum, Cockayne syndrome and trichothiodystrophy. 1472 16

Overall, chemotherapy falls short of the high expectations for improved survival in surgically resected non-small cell lung cancer patients and prolonged survival in the metastatic setting. Conventional chemotherapy trials, even those including new cytotoxic drugs or novel targeting approaches, are hampered by a lack of genetic information. Within the global genomic repair pathway, overexpression of excision repair cross-complementing 1 (ERCC1) has been associated with poor response and survival in cisplatin-treated patients. The lack of DNA adducts in cell nuclei indicates an efficient global genomic repair pathway, which leads to cisplatin resistance. Several xeroderma pigmentosum (XP) genes, including XPD, play an important role in determining the efficiency of the transcription-coupled repair pathway. XPD polymorphism has been related to lower DNA repair capacity and enhanced cisplatin sensitivity. Other DNA repair systems are the base excision repair pathway, in which apurinic/apyrimidinic endonuclease 1 (Ape 1) plays a pivotal role, and the one-step repair pathway, where O(6-)alkylguanine-DNA alkyltransferase (MGMT) has a key function. MGMT methylation can be assessed in serum DNA. By assessing ERCC1 mRNA, cisplatin adducts, XPD polymorphism, Ape 1, and MGMT, we can obtain a complete genetic profile, which can be used in real translational research.
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PMID:Molecular predictors of response to chemotherapy in lung cancer. 1498 77

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.
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PMID:Trichothiodystrophy fibroblasts are deficient in the repair of ultraviolet-induced cyclobutane pyrimidine dimers and (6-4)photoproducts. 1500 40

Mutations in the XPD subunit of the transcription/repair factor TFIIH cause the Xeroderma pigmentosum disorder. We show that in some XP-D deficient cells, transactivation by the vitamin D receptor (VDR) is selectively inhibited for a subset of responsive genes, such as CYP24, and that the XPD/R683W mutation prevents VDR recruitment on its promoter. Contrary to other nuclear receptors, VDR, which lacks a functional A/B domain, is not phosphorylated and consequently not regulated by the cdk7 kinase of TFIIH. In fact, we demonstrate that the VDR transactivation defect resides in Ets1, another activator that cannot be phosphorylated by TFIIH in XP-D cells. Indeed, the phosphorylated Ets1 seems to promote the binding of VDR to its responsive element and trigger the subsequent recruitment of coactivators and RNA pol II. We propose a model in which TFIIH regulates the activity of nuclear receptors by phosphorylating either their A/B domain or an additional regulatory DNA binding partner.
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PMID:Selective regulation of vitamin D receptor-responsive genes by TFIIH. 1549 6

The nucleotide excision repair (NER) is one of the major human DNA repair pathways. Defects in one of the proteins that act in this system result in three distinct autosomal recessive syndromes: xeroderma pigmentosum (XP), Cockayne syndrome (CS) and trichothiodystrophy (TTD). TFIIH is a nine-protein complex essential for NER activity, initiation of RNA polymerase II transcription and with a possible role in cell cycle regulation. XPD is part of the TFIIH complex and has a helicase function, unwinding the DNA in the 5' --> 3' direction. Mutations in the XPD gene are found in XP, TTD and XP/CS patients, the latter exhibiting both XP and CS symptoms. Correction of DNA repair defects of these cells by transducing the complementing wild-type gene is one potential strategy for helping these patients. Over the last years, adenovirus vectors have been largely used in gene delivering because of their efficient transduction, high titer, and stability. In this work, we present the construction of a recombinant adenovirus carrying the XPD gene, which is coexpressed with the EGFP reporter gene by an IRES sequence, making it easier to follow cell infection. Infection by this recombinant adenovirus grants full correction of SV40-transformed and primary skin fibroblasts obtained from XP-D, TTD and XP/CS patients.
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PMID:Restoring DNA repair capacity of cells from three distinct diseases by XPD gene-recombinant adenovirus. 1565 Jul 64

Mutations in the XPD subunit of TFIIH give rise to human genetic disorders initially defined as DNA repair syndromes. Nevertheless, xeroderma pigmentosum (XP) group D (XP-D) patients develop clinical features such as hypoplasia of the adipose tissue, implying a putative transcriptional defect. Knowing that peroxisome proliferator-activated receptors (PPARs) are implicated in lipid metabolism, we investigated the expression of PPAR target genes in the adipose tissues and the livers of XPD-deficient mice and found that (i) some genes are abnormally overexpressed in a ligand-independent manner which parallels an increase in the recruitment of RNA polymerase (pol) II but not PPARs on their promoter and (ii) upon treatment with PPAR ligands, other genes are much less induced compared to the wild type, which is due to a lower recruitment of both PPARs and RNA pol II. The defect in transactivation by PPARs is likely attributable to their weaker phosphorylation by the cdk7 kinase of TFIIH. Having identified the phosphorylated residues in PPAR isotypes, we demonstrate how their transactivation defect in XPD-deficient cells can be circumvented by overexpression of either a wild-type XPD or a constitutively phosphorylated PPAR S/E. This work emphasizes that underphosphorylation of PPARs affects their transactivation and consequently the expression of PPAR target genes, thus contributing in part to the XP-D phenotype.
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PMID:Dysregulation of the peroxisome proliferator-activated receptor target genes by XPD mutations. 1598 19

Defects in the XPD gene can result in several clinical phenotypes, including xeroderma pigmentosum (XP), trichothiodystrophy, and, less frequently, the combined phenotype of XP and Cockayne syndrome (XP-D/CS). We previously showed that in cells from two XP-D/CS patients, breaks were introduced into cellular DNA on exposure to UV damage, but these breaks were not at the sites of the damage. In the present work, we show that three further XP-D/CS patients show the same peculiar breakage phenomenon. We show that these breaks can be visualized inside the cells by immunofluorescence using antibodies to either gamma-H2AX or poly-ADP-ribose and that they can be generated by the introduction of plasmids harboring methylation or oxidative damage as well as by UV photoproducts. Inhibition of RNA polymerase II transcription by four different inhibitors dramatically reduced the number of UV-induced breaks. Furthermore, the breaks were dependent on the nucleotide excision repair (NER) machinery. These data are consistent with our hypothesis that the NER machinery introduces the breaks at sites of transcription initiation. During transcription in UV-irradiated XP-D/CS cells, phosphorylation of the carboxy-terminal domain of RNA polymerase II occurred normally, but the elongating form of the polymerase remained blocked at lesions and was eventually degraded.
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PMID:Transcription-associated breaks in xeroderma pigmentosum group D cells from patients with combined features of xeroderma pigmentosum and Cockayne syndrome. 1613 23

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.
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PMID:Suppression of UV-induced apoptosis by the human DNA repair protein XPG. 1616 68

Epidemiological data has implicated heterozygosity for xeroderma pigmentosum (XP) as a risk factor for lung cancer. XP has 8 known complementation groups, 7 of which are caused by mutations in genes encoding components of the nucleotide excision repair (NER) pathway. To formally investigate the role of XP-related NER genes in lung cancer susceptibility, we screened germline DNA from 92 familial early-onset lung cancer patients for mutations in all coding regions and intron-exon boundaries of XPA, XPC, XPD, XPF, XPB, XPG and DDB2. Forty-one exonic variants were identified. Twenty-four were nonsynonymous, of which 14 were previously documented polymorphisms. Ten missense variants had not been previously described; none of which were detected in germline DNA from 278 cancer-free controls. Two of the novel missense changes are predicted to be functionally deleterious. Our findings are compatible with XP heterozygosity being a risk factor for lung cancer susceptibility.
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PMID:Evaluation of xeroderma pigmentosum XPA, XPC, XPD, XPF, XPB, XPG and DDB2 genes in familial early-onset lung cancer predisposition. 1655 Jun 8

There are more than 50 subtypes of soft tissue sarcomas, among which 30% are associated with specific genetic alterations, including translocations. Several studies have reported associations between cancer risk and polymorphisms of DNA repair genes from the nucleotide excision repair (NER) pathway. NER involves more than 20 proteins whose inactivation leads to xeroderma pigmentosum (XP) or cockayne syndrome (CS), among which XPD, a helicase allowing DNA strand excision by the endonuclease XPG. DNA from 93 patients with synovial sarcomas, myxoid liposarcomas, dermatofibrosarcomas protuberans (DFSP), malignant fibrous histiocytomas and leiomyosarcomas were genotyped for both XPD Lys751Gln and XPG Asp1104His polymorphisms. Departure from Hardy-Weinberg was highly significant for the XPG polymorphism with an excess of heterozygotes in synovial sarcomas (p = 1.5 x 10(-5)), myxoid liposarcomas (p = 1.5 x 10(-4)) and to a lesser extent in DFSP (p = 0.028). In the case of XPD, a significant deviation was observed in synovial sarcomas (p = 3 x 10(-6)) and DFSP (p = 0.0014). When tumors were pooled according to their genetic alterations, the proportion of carriers of the variant XPG allele was significantly increased in sarcomas with specific translocations as compared to sarcomas with complex genetics (p < 10(-9)). No difference was found for XPD. Genotyping of the tumor samples in synovial sarcomas and myxoid liposarcomas revealed frequent loss of heterozygosity for XPG, mostly due to the loss of the frequent allele. For XPD, both alleles were lost with a similar frequency. Our results raise the potential implication of the XPG Asp1104His polymorphism in the occurrence of chromosomal translocations associated with specific subtypes of sarcomas.
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PMID:Genetic polymorphisms of the XPG and XPD nucleotide excision repair genes in sarcoma patients. 1664 69


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