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

Ultraviolet mutagenesis of the shuttle vector plasmid pZ189 in Xeroderma Pigmentosum cells yields a mutational pattern marked by hotspots at photoproduct sites on both strands of the supF marker gene. In order to test the influence of strand orientation on the appearance of hotspots the mutagenesis study was repeated on a vector with the supF gene in the inverted orientation. We recovered a pattern the same as that in the earlier work and conclude that the nature of the DNA polymerase involved in the replication of specific strands is not a primary determinant of hotspot occurrence in this system. One of the hotspots lies in an 8 base palindrome while the corresponding site on the other strand was not a hotspot. These results were obtained with calcium phosphate transfection of the UV treated vector. When DEAE dextran was used as a transfection agent both sites in the palindrome were hotspots. In a mixing experiment the calcium phosphate pattern was recovered. Our data suggest that the sequence determinants of mutational probability at these two sites lie outside the 8 bases of the palindrome and that mutagenesis at one, but not the other, site is sensitive to perturbation of cellular calcium levels.
 ...
PMID:Modulation of an ultraviolet mutational hotspot in a shuttle vector Xeroderma cells. 202 67

The release of DNA 5'-terminal deoxyribose-phosphate residues from enzymatically incised apurinic/apyrimidinic sites by human cell extracts has been under investigation. During the course of these studies, we observed that ataxia telangiectasia cell extracts modify deoxyribose-phosphate (dRp) residues by converting them to an altered form, dRp-X, which shows altered chromatographic properties on HPLC analysis. The chemical nature of the adduct is as yet unknown, but dRp-X is stable to both heat and acid. The modification requires an enzymatic activity and a low-molecular weight co-factor. Extracts of normal cells contain a dialyzable inhibitor that suppresses the reaction occurring with ataxia telangiectasia cell extracts. Formation of dRp-X has been observed in 7 out of 7 ataxia telangiectasia lymphoblastoid lines which represent at least 3 genetic complementation groups. Similar modification of dRp did not occur with extracts of cells of normal origin, nor those representing Fanconi's anaemia, xeroderma pigmentosum, Bloom's syndrome, Werner's syndrome or Friedreich's ataxia.
 ...
PMID:Modification of deoxyribose-phosphate residues by extracts of ataxia telangiectasia cells. 236 95

202 MHz 31P NMR (11.7 T) was used to study the effects of culture medium pH on the levels of phosphate metabolites in three human tumor cell lines (XP29MAmal, a malignant xeroderma pigmentosum; CX-1, a colon carcinoma; KB, a squamous cell carcinoma of the oral cavity). Cells were cultured in Roux flasks in HAM's F-12 medium, and the pH was varied with the final medium change. After harvesting, 1-5 x 10(8) cells were suspended in Ringer/HEPES buffer at pH 7.4 and 4 degrees C for 31P NMR studies. Cell adhesion and growth rate decreased with decreasing pH, but, down to ca pH 6.1, trypan blue exclusion and the observed levels of nucleoside di- and triphosphates (range: 22-37% of total phosphates detected), phosphocreatine (PCr, 2-5%) and Pi (5-11%) did not vary significantly with pH. For XP29MAmal cells in exponential growth phosphocholine levels decreased from 18-28% at pH 7.0 to ca 5% at pH 6.0, while phosphoethanolamine levels increased from 2-7% to 15%. Glycerophosphocholine (GPC) levels increased from ca 7% at pH 7.2 to 13% at pH 6.3. At pH less than 6.3 cytidine 5'-diphosphate (CDP) choline became detectable (8-16%, delta p:P alpha = -8.13 ppm, P beta = 8.93 ppm, for PCr = 0 ppm). However, confluent cells did not accumulate CDP-choline when the pH was lowered. The cell lines CX-1 and KB also showed the pH effects described herein.
 ...
PMID:31P NMR studies of cultured human tumor cells. Influence of pH on phospholipid metabolite levels and the detection of cytidine 5'-diphosphate choline. 239 Apr 57

A cDNA expression vector containing the element oriP and the sequence encoding the Epstein-Barr virus (EBV) nuclear antigen 1 (EBNA-1) as well as the hygromycin B-resistance dominant marker gene has been constructed. Its characteristics have been compared to a similar vector lacking the EBV sequences. (a) The EBV+ vector is maintained as an episome with a copy number of approx. 50 per cell, whereas the number of the integrated EBV- copies is in general smaller than 10, when simian virus 40-transformed xeroderma pigmentosum fibroblasts (XP20S-SV) constitute the recipient cell line. (b) The presence of the EBV sequences in the vector resulted in a five- to ten-fold higher transfection efficiency with the Ca.phosphate precipitation technique. (c) cDNA inserts in the EBV+ vector are shown to be efficiently and properly expressed in the recipient cell. (d) If transfection is performed with a mixture of EBV+ vectors with different inserts, transfectants are shown to harbour different plasmids within one cell. (e) The ratio between these plasmids in one cell can be shifted in favour of a vector with a particular insert, when selection for this insert is performed. (f) Reconstruction experiments indicated that isolation of a low-abundance sequence from a mixture of vectors is at least 100-fold more efficient with the EBV+ system, than with the EBV- system. (g) Rescue of the episomal vector from transfected cells can be readily achieved.
 ...
PMID:Construction and properties of an Epstein-Barr-virus-derived cDNA expression vector for human cells. 248 30

We have examined several parameters which address the feasibility of complementing the UV-sensitive phenotype of xeroderma pigmentosum (XP) fibroblasts by gene transfer. We present a comparative study which demonstrates that, relative to immortalized cells, human diploid cells are poor recipients for gene transfer. As measured by both transient and stable expression assays, diploid fibroblasts were completely refractory to DNA transfer by calcium phosphate coprecipitation and exhibited substantially reduced levels of expression following gene transfer by fusion with E. coli protoplasts. We also examined the significance of reversion of the phenotype of UV sensitivity in SV40-immortalized XP-A cell lines. In addition to confirming a previous report of reversion to wild-type levels of UV resistance at a frequency of approximately 10(-7), we have attempted to facilitate the identification of XP-A cells complemented with genomic DNA by employing less stringent selection schemes and cotransfection of a selectable marker. Under these conditions, we observed an increased frequency of reversion and were unable to identify true transfectants.
 ...
PMID:Studies on gene transfer and reversion to UV resistance in xeroderma pigmentosum cells. 300 3

In previous work, a xeroderma pigmentosum cell line belonging to complementation group C was established by transformation with origin-defective simian virus 40. We now report the complementation of the UV sensitivity of this cell line by gene transfer. A human cDNA clone library constructed in a mammalian expression vector, and itself incorporated in a lambda phage vector, was introduced into the cells as a calcium phosphate precipitate. Following selection to G418 resistance, provided by the neo gene of the vector, transformants were selected for UV resistance. Twenty-one cell clones were obtained with UV-resistance levels typical of normal human fibroblasts. All transformants contained vector DNA sequences in their nuclei. Upon further propagation in the absence of selection for G418 resistance, about half of the primary transformants remained UV-resistant. Secondary transformants were generated by transfection with a partial digest of total chromosomal DNA from one of these stable transformants. This resulted in 15 G418-resistant clones, 2 of which exhibited a UV-resistant phenotype. The other primary clones lost UV resistance rapidly when subcultured in the absence of G418. Importantly, several retained UV resistance under G418 selection pressure. The acquisition of UV resistance by secondary transformants derived by transfection of DNA from a stable primary transformant, and the linkage between G418 and UV resistances in the unstable primary transformants, strongly suggests that the transformants acquired UV resistance through DNA-mediated gene transfer and not by reversion.
 ...
PMID:Complementation of the UV-sensitive phenotype of a xeroderma pigmentosum human cell line by transfection with a cDNA clone library. 348 May 11

Xeroderma pigmentosum (XP) is an inherited disease characterized by the defective repair of DNA damaged by ultraviolet radiation and a number of chemicals. In this paper, plasmid DNA carrying a marker gene is cross-linked in vitro by the antitumor drug cisplatin and successfully introduced into tissue culture cells by both calcium phosphate coprecipitation and electroporation. Transient expression of the marker gene is greatly decreased in XP cells compared to wild-type. As few as seven lesions will inactivate the marker gene in XP cells. Furthermore, the biochemical defect must include an impaired capacity for repair of cisplatin-DNA intrastrand cross-links. Since the host cell itself is not exposed to chemical modification, a cisplatin cross-linked plasmid shuttle vector can be used as a specific probe for the DNA repair capacity of cultured cells. Paradoxically, when cisplatin cross-linked plasmid carrying the selectable marker neo is introduced into cells, there is an increase in the number of stable neo+ transformants in both XP and wild-type cells. Thus, cisplatin damage appears to stimulate the integration of transfected DNA into the host chromosome by a mechanism that is independent of the defective repair pathway in XP.
 ...
PMID:DNA cross-linked by cisplatin: a new probe for the DNA repair defect in xeroderma pigmentosum. 369 39

Irradiation with UV-A of normal human fibroblasts in phosphate-buffered saline induced cell death, measured as lack of colony-forming ability. A specially filtered sunlamp, emitting wavelengths greater than 330 nm, was used as UV-A source. After UV-A irradiation, single-strand breaks (alkali-labile bonds) could be detected in DNA; these lesions were rapidly repaired. The induction of these single-strand breaks was almost eliminated when irradiation was performed in the presence of catalase. However, catalase, when present during UV-A irradiation, did not reduce cell death of the fibroblasts. Excision repair, monitored as unscheduled DNA synthesis, was induced strongly by irradiation with UV-C (predominantly 254 nm), but could not be detected after UV-A irradiation. Moreover, very little accumulation of incision breaks during post-irradiation incubation with hydroxyurea and 1-beta-D-arabinofuranosylcytosine (araC) was detected after UV-A. This is consistent with the low amount of pyrimidine dimers (measured as UV-endonuclease susceptible sites) induced by UV-A. Xeroderma pigmentosum fibroblasts of complementation group A, which are extremely sensitive to UV-C irradiation, showed the same sensitivity to UV-A as normal fibroblasts. The results indicate that lethality by UV-A wavelengths greater than 330 nm is caused by lesions other than single-strand breaks (alkali-labile bonds) and pyrimidine dimers.
 ...
PMID:The induction and repair of DNA damage and its influence on cell death in primary human fibroblasts exposed to UV-A or UV-C irradiation. 400 Jan 50

The formation and repair of alkali-labile sites in the DNA of human cells treated with 254 nm u.v. light, 1'-acetoxyestragole (1'-AcO-E) or 1'-acetoxysafrole (1'-AcO-S) have been studied. DNA was analysed by sedimentation in alkaline sucrose gradients after the cells had been layered on the gradients in lysis solution for 15 h (long lysis) or for only 0.75 h (short lysis). With the long lysis technique, a dose of 20 J/m2 resulted in 0.2-0.4 strand breaks/10(8) daltons while treatment of cells with 0.5 mM 1'-AcO-E or 1'-AcO-S caused 0.1-0.3 strand breaks/10(8) daltons. In excision repair proficient T98G cells, one third to two thirds of these strand breaks disappeared upon 4 h incubation after exposure to each of the three agents. In excision repair deficient xeroderma pigmentosum fibroblasts (XPA), the alkali-labile sites produced by 1'-AcO-E or 1'-AcO-S were still repaired, although those resulting from u.v.-irradiation were not. Similar characteristics were observed after the short lysis period. The sedimentation velocities of nucleoids, prepared from treated XPA cells, in neutral sucrose gradients containing ethidium bromide, did not reveal the presence of overt strand breaks in the DNA, suggesting that the lesions were of a type in which the sugar-phosphate backbone was intact but sensitive to hydrolysis by alkali. The contribution of this type of damage to the total DNA damage produced by the agents was estimated to be less than 1% for u.v., and less than 2.5% for 1'-AcO-E and 1'-AcO-S.
 ...
PMID:Alkali-sensitive sites in DNA from human cells treated with ultraviolet light, 1'-acetoxysafrole or 1'-acetoxyestragole. 712 74

We showed that DNA-dependent ATPase Q1 (DNA helicase Q1) from xeroderma pigmentosum complementation group C (XP-C) cells elutes from FPLC Mono Q column at higher concentrations of KCl than that from other human cells (35). We purified DNA helicase Q1 from XP-C and HeLa cells. The purified fractions of both cells contained a major polypeptide with a molecular mass of 73 kDa and had the same enzymatic properties, including salt- and temperature-sensitivity. Characterization using an anti-DNA helicase Q1 antibody indicated that this enzyme localized in the nuclei and was not modified by incorporating phosphate groups through phosphorylation and ADP-ribosylation. No interactions of DNA helicase Q1 with other proteins were indicated by immunoprecipitation of the helicase from crude extracts. No difference was observed in XP-C cells in intracellular localization of DNA helicase Q1, phosphorylation, and the interaction with other proteins as compared to HeLa cells.
 ...
PMID:Characterization of the properties of a human homologue of Escherichia coli RecQ from xeroderma pigmentosum group C and from HeLa cells. 879 Sep 42


1 2 Next >>