Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Various DNA alterations can be caused by exposure to environmental and endogenous carcinogens. Most of these alterations, if not repaired, can result in genetic instability, mutagenesis and cell death. DNA repair mechanisms are important for maintaining DNA integrity and preventing carcinogenesis. Recent lung cancer studies have focused on identifying the effects of single nucleotide polymorphisms (SNPs) in candidate genes, among which DNA repair genes are increasingly being studied. Genetic variations in DNA repair genes are thought to modulate DNA repair capacity and are suggested to be related to lung cancer risk. We identified a sufficient number of epidemiologic studies on lung cancer to conduct a meta-analysis for genetic polymorphisms in nucleotide excision repair pathway genes, focusing on xeroderma pigmentosum group A (XPA), excision repair cross complementing group 1 (ERCC1), ERCC2/XPD, ERCC4/XPF and ERCC5/XPG. We found an increased risk of lung cancer among subjects carrying the ERCC2 751Gln/Gln genotype (odds ratio (OR) = 1.30, 95% confidence interval (CI) = 1.14 - 1.49). We found a protective effect of the XPA 23G/G genotype (OR = 0.75, 95% CI = 0.59 - 0.95). Considering the data available, it can be conjectured that if there is any risk association between a single SNP and lung cancer, the risk fluctuation will probably be minimal. Advances in the identification of new polymorphisms and in high-throughput genotyping techniques will facilitate the analysis of multiple genes in multiple DNA repair pathways. Therefore, it is likely that the defining feature of future epidemiologic studies will be the simultaneous analysis of large samples.
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PMID:Genetic polymorphisms in the nucleotide excision repair pathway and lung cancer risk: a meta-analysis. 1729 78

Mutations in the human XPG gene give rise to an inherited photosensitive disorder, xeroderma pigmentosum (XP) associated with Cockayne syndrome (XP-G/CS). The clinical features of CS in XP-G/CS patients are difficult to explain on the basis of a defect in nucleotide excision repair (NER). We found that XPG forms a stable complex with TFIIH, which is active in transcription and NER. Mutations in XPG found in XP-G/CS patient cells that prevent the association with TFIIH also resulted in the dissociation of CAK and XPD from the core TFIIH. As a consequence, the phosphorylation and transactivation of nuclear receptors were disturbed in XP-G/CS as well as xpg(-/-) MEF cells and could be restored by expression of wild-type XPG. These results provide an insight into the role of XPG in the stabilization of TFIIH and the regulation of gene expression and provide an explanation of some of the clinical features of XP-G/CS.
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PMID:XPG stabilizes TFIIH, allowing transactivation of nuclear receptors: implications for Cockayne syndrome in XP-G/CS patients. 1746 19

The XPB DNA helicase, a subunit of the basal transcription factor TFIIH, is also involved in nucleotide excision repair (NER). We examined recruitment of NER proteins in XP-B cells from patients with mild or severe xeroderma pigmentosum (XP) having different XPB mutations using local UV-irradiation through filters with 5 microm pores combined with fluorescent antibody labeling. XPC was rapidly recruited to UV damage sites containing DNA photoproducts (cyclobutane pyrimidine dimers, CPD) in all the XP-B and normal cells, thus reflecting its role in damage recognition prior to the function of XPB. Cells from the mild XP-B patients, with a missense mutation, showed delayed recruitment of all NER proteins except XPC to UV damage sites, demonstrating that this mutation impaired localization of these proteins. Surprisingly, in cells from severely affected patients, with a C-terminal XPB mutation, XPG and XPA proteins were normally recruited to UV damage sites demonstrating that this mutation permits recruitment of XPG and XPA. In marked contrast, in all the XP-B cells recruitment of XPF was absent immediately after UV and was delayed by 0.5 and 3 h in cells from the mild and severely affected XP patients, respectively. Redistribution of NER proteins was nearly complete in normal cells by 3 h but by 24 h redistribution was only partially present in cells from mild patients and virtually absent in cells from the severely affected patients. Ineffectual repair of UV-induced photoproducts resulting from delayed recruitment and impaired redistribution of NER proteins may contribute to the markedly increased frequency of skin cancer in XP patients.
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PMID:Influence of XPB helicase on recruitment and redistribution of nucleotide excision repair proteins at sites of UV-induced DNA damage. 1750 50

The Xeroderma Pigmentosum group C (XPC) protein is indispensable to global genomic repair (GGR), a subpathway of nucleotide excision repair (NER), and plays an important role in the initial damage recognition. XPC can be modified by both ubiquitin and SUMO in response to UV irradiation of cells. Here, we show that XPC undergoes degradation upon UV irradiation, and this is independent of protein ubiquitylation. The subunits of DDB-Cul4A E3 ligase differentially regulate UV-induced XPC degradation, e.g DDB2 is required and promotes, whereas DDB1 and Cul4A protect the protein degradation. Mutation of XPC K655 to alanine abolishes both UV-induced XPC modification and degradation. XPC degradation is necessary for recruiting XPG and efficient NER. The overall results provide crucial insights regarding the fate and role of XPC protein in the initiation of excision repair.
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PMID:Ubiquitylation-independent degradation of Xeroderma pigmentosum group C protein is required for efficient nucleotide excision repair. 1769 35

Benzo[a]pyrene (BaP) is a ubiquitously distributed environmental pollutant known to cause DNA damage, which may be repaired through nucleotide excision repair (NER). However, little is known about dynamic changes in levels of DNA damage and their correlations with levels of NER proteins in cells exposed to BaP. In a series of experiments using the human bronchial epithelia cells (16HBE) exposed to different concentrations of BaP for different times, we measured dynamic changes in levels of DNA damage and expression of NER subunit xeroderma pigmentosum (XP) groups A, C, F, G (XPA, XPC, XPF, XPG) and excision repair cross-complementing 1 (ERCC1), and analyzed their possible correlations. We found that in vitro exposure to BaP reduced cell viability in a dose-dependent manner ranging from 2 to 64microM and increased DNA damage in a dose- and time-dependent manner. Our results showed that levels of these NER proteins significantly increased and peaked at 12th or 24th, 8th or 12th and 4th or 8th hours in cells exposed to 2, 8 and 16microM BaP, respectively. ERCC1 expression increased by 2.4-, 4.2- and 19.3-fold for exposure to 2, 8 and 16microM BaP, respectively, compared with control group. Moreover, levels of ERCC1 in cells exposed 16microM BaP significantly higher than those in 2 and 8microM BaP from 2nd to 48th hours. In addition, there was a significant positive correlation between Olive tail moments and relative ratios of ERCC1 in cells exposed to BaP. Our results suggested ERCC1 may be an important limiting factor for NER, but the mechanisms underlying this observation needs further investigation.
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PMID:Dynamic changes of XPA, XPC, XPF, XPG and ERCC1 protein expression and their correlations with levels of DNA damage in human bronchial epithelia cells exposed to benzo[a]pyrene. 1790 Aug 31

Nucleotide excision repair (NER) eliminates helix-distorting DNA base lesions. Seven XP-deficient genetic complementation groups (XPA to XPG) have already been identified in mammals, and their corresponding genes have been cloned. Hereditary defects in NER are associated with several diseases, including xeroderma pigmentosum (XP). UV-DDB (XPE) is formed by two associated subunits, DDB1 and DDB2. UV-DDB was identified biochemically as a protein factor that exhibits very strong and specific binding to ultraviolet (UV)-treated DNA. As a preliminary step to characterize the components of the NER in the filamentous fungus Aspergillus nidulans, here we identified a putative DDB1 homologue, DdbA. Deletion and expression analysis indicated that A. nidulans ddbA gene is involved in the DNA damage response, more specifically in the UV light response and 4-nitroquinoline oxide (4-NQO) sensitivity. Furthermore, the DeltaddbA strain cannot self-cross and expression analysis showed that ddbA can be induced by oxidative stress and is developmentally regulated in both asexual and sexual processes. The DeltaddbA mutation can genetically interact with uvsB (ATR), atmA(ATM), nkuA (KU70), H2AX-S129A (a replacement of the conserved serine in the C-terminal of H2AX with alanine), and cshB (a mutation in CSB Cockayne's syndrome protein involved in the transcription-coupled repair subpathway of NER) mutations. Finally, to determine the DdbA cellular localization, we constructed a GFP::DdbA strain. In the presence and absence of DNA damage, DdbA was mostly detected in the nuclei, indicating that DdbA localizes to nuclei and its cellular localization is not affected by the cellular response to DNA damage induced by 4-NQO and UV light.
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PMID:Functional characterization of the putative Aspergillus nidulans DNA damage binding protein homologue DdbA. 1806 Apr 32

Alterations in genes involved in nucleotide excision repair (NER) are associated with three genetic disorders, xeroderma pigmentosum (XP), Cockayne syndrome (CS) and trichothiodystrophy (TTD). The transcription and repair factor TFIIH is a central component of NER and mutations of its subunits are associated with all three diseases. A recent report provides a molecular basis for how mutations in the NER endonuclease XPG that affect the interaction of TFIIH might give rise to CS features. In cells of XP-G patients with a combined XP and CS phenotype, XPG fails to associate with TFIIH and as a consequence the CAK subunit dissociates from core TFIIH. A simplified, but general model of how various assembly and disassembly states of TFIIH can be invoked to explain different disease states is discussed. Accordingly, defects in specific enzymatic functions typically result in XP, dissociation of the CAK subunit from TFIIH is associated with XP/CS and a more generalized destabilization of TFIIH gives rise to TTD. While this classification provides a useful framework to understand how alterations in TFIIH correlate with disease states, it does not universally apply and relevant exception and alternative explanations are discussed.
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PMID:Hot topics in DNA repair: the molecular basis for different disease states caused by mutations in TFIIH and XPG. 1807 23

Xeroderma pigmentosum (XP) is an autosomal recessive disease, which is characterized by susceptibility to ultraviolet light (UV)-induced skin cancer. Among eight genes so far identified as responsible for XP, XPA through XPG are involved in nucleotide excision repair of DNA damage induced by UV as well as various chemical carcinogens. Since this repair system removes a major UV photoproduct, the cyclobutane pyrimidine dimer, quite slowly from the global genome, this lesion must be accurately bypassed during replication by DNA polymerase eta, encoded by the XPV gene. Recent studies have revealed that each of these XP genes possesses additional functions, some of which are concerned with other DNA repair pathways and/or cellular DNA damage responses. Such differential functions not only explain clinical heterogeneity among different genetic complementation groups but also have implications for the promotion of carcinogenic processes in XP patients.
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PMID:Xeroderma pigmentosum genes: functions inside and outside DNA repair. 1817 45

Molecular profiling of markers involved in the activity of chemotherapeutic agents can shed light on the successes and failures of treatment in patients and can also provide a basis for individualization of therapy. Toward those ends, we have used reverse-phase protein lysate microarrays to evaluate expression of protein components of the nucleotide excision repair (NER) pathways. Those pathways strongly influence the anticancer activities of numerous drugs, including those that are the focus here, cisplatin and ecteinascidin 743 (Et-743; Yondelis, Trabectedin). Cisplatin is generally more active in cell types deficient in NER, whereas Et-743 tends to be less active in those cells. We measured protein expression and sensitivity to those drugs in 17 human ovarian and colon cancer cell lines (13 of them from the NCI-60 panel) and five xeroderma pigmentosum (XP) patient cell types, each containing a different NER defect. Of the NER proteins giving reliable signals, XPF and XPG showed the highest correlations of protein expression with drug activity across all three tissue-of-origin groups. When we compared protein expression data with mRNA expression data from Affymetrix U133A chips, we found no consistent correlation between the two across the cell lines studied, which reinforces the conclusion that protein measurements can give more interpretable mechanistic information than can transcript measurements. The work reported here provides motivation for larger proteomic studies with more cell types focused on potential biomarkers in additional pharmacologically pertinent pathways.
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PMID:Predicting cisplatin and trabectedin drug sensitivity in ovarian and colon cancers. 1818 10

Xeroderma pigmentosum (XP) is a rare DNA repair disorder characterized by extreme sensitivity to sunlight and severe predisposition to UV-induced skin cancer. Seven genes, ranging from XPA to XPG, are defective in XP. These genes are important components of the nucleotide excision repair (NER) system, which removes DNA damage induced by solar radiation, thereby preventing genome instability and carcinogenesis. In addition, XPV patients are defective in a translesion synthesis activity specialized in bypassing UV-induced lesions, and share symptoms with other XP patients. This review will focus on the evidence that elucidates the link between defective NER, genetic instability, and oncogenesis.
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PMID:Xeroderma pigmentosum: a glimpse into nucleotide excision repair, genetic instability, and cancer. 1819 91


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