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)

Once a large proportion of the genes responsible for genetic disorders are identified in the post-genome era, the fundamental challenge is to establish a genotype/phenotype relationship. Our aim is to explain how mutations in a given gene affect its enzymatic function and, in consequence, disturb the life of the cell. Genome integrity is continuously threatened by the occurrence of DNA damage arising from cellular exposure to irradiation and genotoxic chemicals. This mutagenic or potentially lethal DNA damage induces various cellular responses including cell cycle arrest, transcription alteration and processing by DNA repair mechanisms, such as the nucleotide excision repair (NER) pathway. Disruption of NER in response to genotoxic injuries results in autosomal recessive hereditary diseases such as Xeroderma pigmentosum (XP), Cockayne syndrome (CS) and trichothiodystrophy (TTD). One of the most immediate consequences of the induction of strand-distorting lesions is the arrest of transcription in which TFIIH plays a role in addition to its role in DNA repair. The observations made by clinicians close to XP, TTD and CS patients, suggested that transcription defects responsible for brittle hair and nails for TTD, or developmental abnormalities for CS, resulted from TFIIH mutations. Here a story will be related which could be called 'a multi-faceted factor named TFIIH'. As biochemists, we have characterized each component of TFIIH, three of which are XPB and XPD helicases and cdk7, a cyclin-dependent kinase. With the help of structural biologists, we have characterized most of the specific three-dimensional structures of TFIIH subunits and obtained its electron microscopy image. Together these approaches help us to propose a number of structure-function relationships for TFIIH. Through transfection and microinjection assays, cell biology allows us to determine the role of TFIIH in transcription and NER. We are thus in a position to explain, at least in part, transcription initiation mechanisms and their coupling to DNA repair. We now know how the XPB helicase opens the promoter region for RNA synthesis and that one of the roles of XPD helicase is to anchor the cdk7 kinase to the core-TFIIH. In XP and CS associated patients, we have demonstrated that some XPD mutations prevent an optimal phosphorylation of nuclear receptors by cdk7 with, as a consequence, a drop in the expression of genes sensitive to hormone action. We have thus shown that hormonal responses operate through TFIIH. Careful analysis of each TFIIH subunit also shows how the p44 Ring finger participates in certain promoter escape reactions. We are also able to localize the action of TFIIH in the sequence of events that lead to the elimination of DNA lesions. Thanks to the combination of these different approaches we are obtaining a much clearer picture of the TFIIH complex and its integration into the life of the cell.
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PMID:The 14th Datta Lecture. TFIIH: from transcription to clinic. 1141 42

ERCC2 [Xeroderma pigmentosum (XP) group D] belongs to the nucleotide excision repair pathway. It is also part of the TFIIH transcription complex and is required for the association of the cyclin-dependent kinase (CDK)-activating kinase (CAK) subcomplex with TFIIH. Using the NCI-60 panel of human tumor cell lines, we had shown that the ERCC2 gene variant Gln(751) was significantly associated to increased taxanes sensitivity and decreased ERCC2 gene expression. Since TFIIH is involved in both DNA repair and cell cycle progression, we hypothesized that quantitative or qualitative ERCC2 alterations might cause CAK liberation, allowing its activation of the G(2)/M transition. Enhancing mitosis entry would lead to hypersensitivity to spindle poisons, explaining the effect of ERCC2 polymorphisms on taxane sensitivity. Starting from ERCC2-deficient XP6BE, we generated several isogenic clones differing only by the Lys751Gln variation. Wild-type and variant ERCC2-expressing clones recovered ultraviolet radiation and cisplatin resistance but presented similar sensitivity to paclitaxel, demonstrating that the amino acid change was not involved in paclitaxel differential sensitivity in the NCI-60 panel. Using small interfering RNA approach, we knocked down ERCC2 expression and observed a block in the G(2)/M phase, with a consistent increase in paclitaxel sensitivity and no change in cisplatin sensitivity. We observed in addition an increase in CDK1 activity, as evaluated by histone H1 phosphorylation. We evaluated messenger RNA (mRNA) half-life in the isogenic lines and observed a more rapid degradation in cells bearing the variant construct. We concluded that the increased paclitaxel sensitivity of ERCC2 variant cell lines is a consequence of lower gene expression, likely due to decreased stability of the variant ERCC2 mRNA.
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PMID:Deciphering the role of the ERCC2 gene polymorphism on anticancer drug sensitivity. 2234 63

The xeroderma pigmentosum group D (XPD) helicase is a subunit of transcription/DNA repair factor, transcription factor II H (TFIIH) that catalyzes the unwinding of a damaged DNA duplex during nucleotide excision repair. Apart from two canonical helicase domains, XPD is composed of a 4Fe-S cluster domain involved in DNA damage recognition and a module of uncharacterized function termed the "ARCH domain." By investigating the consequences of a mutation found in a patient with trichothiodystrophy, we show that the ARCH domain is critical for the recruitment of the cyclin-dependent kinase (CDK)-activating kinase (CAK) complex. Indeed, this mutation not only affects the interaction with the MAT1 CAK subunit, thereby decreasing the in vitro basal transcription activity of TFIIH itself and impeding the efficient recruitment of the transcription machinery on the promoter of an activated gene, but also impairs the DNA unwinding activity of XPD and the nucleotide excision repair activity of TFIIH. We further demonstrate the role of CAK in downregulating the XPD helicase activity within TFIIH. Taken together, our results identify the ARCH domain of XPD as a platform for the recruitment of CAK and as a potential molecular switch that might control TFIIH composition and play a key role in the conversion of TFIIH from a factor active in transcription to a factor involved in DNA repair.
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PMID:ARCH domain of XPD, an anchoring platform for CAK that conditions TFIIH DNA repair and transcription activities. 2338 12