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)

The activities of DNA polymerases alpha, beta, and gamma were determined in control and repair-deficient human fibroblasts (xeroderma pigmentosum complementation groups A, C, and D; Fanconi's Anemia; and Bloom's syndrome). Assays were done on 103,000XG supernatants which had been chromatographed on DEAE cellulose to remove nucleic acids and on fractions containing polymerase activities which had been separated from one another on a second DEAE cellulose column. All repair-deficient cell types contained all three DNA polymerase activities. Caffeine, which has been observed to inhibit some DNA-repair processes in intact cells, had no effect on DNA polymerase activities from XP-A, XP-C, XP-D or XP-variant cells. These data indicate that all three polymerases are present in cells which have reduced or absent repair functions and that the caffeine effects observed in living cells are probably not due to the direct action of caffeine on DNA polymerases.
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PMID:Levels of DNA polymerases alpha, beta, and gamma in control and repair-deficient human diploid fibroblasts 1. 89 83

An assay has been developed to measure the ability of human lymphocytes to repair damage to DNA. In this assay, purified human lymphocytes are exposed to graded doses of radiation and then stimulated with phytohemagglutinin to undergo DNA replication. The rate of incorporation of thymidine in irradiated lymphocytes during the second and subsequent rounds of DNA replication is taken to be indicative of the ability of the cells to repair damage to DNA. In lymphocytes from normal individuals, X-irradiation with doses of 100 to 800 rads was found to inhibit phytohemagglutinin-stimulated thymidine incorporation proportionally to the dose of radiation without curtailing the induction of DNA polymerase. The response to phytohemagglutinin of lymphocytes from a patient with xeroderma pigmentosum after exposure to graded doses of X-irradiation was found to be similar to that of the normal controls, whereas the response after ultraviolet irradiation was markedly impaired. In contrast, lymphocytes from patients with ataxia telangiectasia were hypersensitive to X-irradiation. The data on these clinical syndromes support the idea that this assay measures DNA repair and indicates the feasibility of using this method for screening individuals for genetic deficits in DNA repair.
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PMID:Screening for deficits in DNA repair by the response of irradiated human lymphocytes to phytohemagglutinin. 90 9

The mutagenic spectrum induced by aflatoxin-DNA lesions in DNA repair deficient and repair proficient human cells was investigated. The reactive metabolite aflatoxin B1-8,9-epoxide was synthesized and reacted in vitro with the shuttle vector plasmid pS189. Plasmids were transfected into human fibroblasts and allowed to replicate, and the recovered plasmids were screened in indicator bacteria for plasmid survival and mutations in the supF marker gene. Sequence data were obtained from 71 independently arising mutants recovered from DNA repair deficient xeroderma pigmentosum (XP) cells [XP12BE(SV40)] and 60 mutants recovered from a DNA repair proficient cell line (GM0637). Plasmid survival was lower and mutation frequency higher with the XP cells, and the mutation hotspots differed substantially for the 2 cell lines. Most mutations (> 90%) were base substitutions at G:C pairs, only about one-half of which were G:C-->T:A transversions, the expected predominant mutation. One-third of the mutations at GG sites and none of those at isolated Gs were G:C-->A:T transitions. Tandem base substitutions also occurred only at GG sites and were found only with XP cells. The location of mutation hotspots with either cell line did not correlate with the level of modification within the sequence as assessed by a DNA polymerase stop assay. These results suggest that the DNA repair deficiency associated with XP can influence not only the overall frequency of mutations but also the distribution of mutations within a gene. The finding of transition mutations exclusively at GG sites may be of predictive value in attempts to link dietary aflatoxin exposure to cancers associated with specific mutations in the c-ras oncogene and the p53 tumor suppressor gene.
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PMID:Sequence specificity of aflatoxin B1-induced mutations in a plasmid replicated in xeroderma pigmentosum and DNA repair proficient human cells. 139 91

The human single-stranded DNA binding protein (HSSB/RPA) is involved in several processes that maintain the integrity of the genome including DNA replication, homologous recombination, and nucleotide excision repair of damaged DNA. We report studies that analyze the role of HSSB in DNA repair. Specific protein-protein interactions appear to be involved in the repair function of HSSB, since it cannot be replaced by heterologous single-stranded DNA binding proteins. Anti-HSSB antibodies that inhibit the ability of HSSB to stimulate DNA polymerase alpha also inhibit repair synthesis mediated by human cell-free extracts. However, antibodies that neutralize DNA polymerase alpha do not inhibit repair synthesis. Repair is sensitive to aphidicolin, suggesting that DNA polymerase epsilon or delta participates in nucleotide excision repair by cell extracts. HSSB has a role other than generally stimulating synthesis by DNA polymerases, as it does not enhance the residual damage-dependent background synthesis displayed by repair-deficient extracts from xeroderma pigmentosum cells. Significantly, when damaged DNA is incised by the Escherichia coli UvrABC repair enzyme, human cell extracts can carry out repair synthesis even when HSSB has been neutralized with antibodies. This suggests that HSSB functions in an early stage of repair, rather than exclusively in repair synthesis. A model for the role of HSSB in repair is presented.
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PMID:A role for the human single-stranded DNA binding protein HSSB/RPA in an early stage of nucleotide excision repair. 150 73

Human fibroblasts repair DNA damaged by bleomycin through both short-patch and long-patch pathways, mediated by an aphidicolin-resistant (beta) and aphidicolin-sensitive (delta) DNA polymerase respectively (DiGiuseppe, J.A. and Dresler, S.L. (1989) Biochemistry, 28, 9515-9520). Despite certain similarities, aphidicolin-sensitive repair synthesis induced by bleomycin can be distinguished genetically and biochemically from that elicited by UV radiation. Permeable xeroderma pigmentosum fibroblasts of complementation groups A and G, completely deficient in UV-induced repair, display aphidicolin-sensitive repair synthesis dependent upon dose of bleomycin. Furthermore, the ribonucleotide dependence of long-patch repair induced by bleomycin differs from that of UV repair with respect to substrate specificity and apparent Km for ATP. This novel ATPase activity mediates a step prior to polymerization. By contrast, short-patch repair synthesis does not require ATP. These data suggest that, in addition to short-patch repair, human cells possess two distinct long-patch excision repair pathways. We propose that these pathways represent strand-break, base and nucleotide excision repair respectively.
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PMID:Aphidicolin-sensitive DNA repair synthesis in human fibroblasts damaged with bleomycin is distinct from UV-induced repair. 169 20

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.
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PMID:Modulation of an ultraviolet mutational hotspot in a shuttle vector Xeroderma cells. 202 67

First generation progeny herpes simplex type 1 (HSV-1) virions grown in the presence of 5-iodo-2'-deoxyuridine (IdUrd) were irradiated with either 254 or 302 nm ultraviolet (u.v.) light. The kinetics of virus inactivation revealed decreased sensitivity of IdUrd-substituted virions to irradiation with 302 nm light under all conditions examined, and with 254 nm u.v. light when substituted and control virions were irradiated at equal particle concentrations. Comparison of virus survival after irradiation measured in Vero or Xeroderma Pigmentosum (complementation group A) cells indicated that cellular repair of ultraviolet-induced lesions was not a significant factor in the observed decrease in u.v. sensitivity. IdUrd substitution altered neither the formation of ultraviolet-induced thymidine photoproducts nor the ability of irradiated virions to express delayed early viral enzymes (thymidine kinase, DNA polymerase). It is suggested that nucleocapsid proteins or the highly ordered structure of IdUrd-substituted virions play a key role in u.v. desensitization, either by the formation of non-lethal photoproducts or by the prevention of the formation of DNA-uracilyl free radicals.
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PMID:Effect of incorporation of 5-iodo-2'-deoxyuridine into HSV-1 DNA on virion sensitivity to ultraviolet light. 282 22

Those pyrimidine dimers that are repaired in confluent xeroderma pigmentosum Group C cells are clustered together in the genome. Although the average level of repair in this complementation group is of the order of 25% of normal, this percentage represents normal levels of repair in one quarter of the genome and little repair in the remainder. The factors that regulate this clustering process have been investigated using inhibitors of the initial incision step of repair (novobiocin) and of the polymerization step (aphidicolin). Novobiocin at a concentration that permitted 30% of repair to continue reduced the clustering of mended sites only slightly. Aphidicolin, in contrast, at a concentration that permitted 30 to 60% of repair to continue caused the mended sites to be distributed randomly. The clustering of repair sites seen in xeroderma pigmentosum Group C cells, therefore, is produced by an excision repair mechanism in which an aphidicolin-sensitive DNA polymerase, presumably alpha, plays an important regulatory role in determining which damaged sites are mended.
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PMID:Relative importance of incision and polymerase activities in determining the distribution of damaged sites that are mended in xeroderma pigmentosum group C cells. 310 77

When UV-irradiated cultured diploid human fibroblasts were permeabilized with Brij-58 then separated from soluble material by centrifugation, conservative DNA repair synthesis could be restored by a soluble factor obtained from the supernatant of similarly treated HeLa cells. Extensive purification of this factor yielded a 10.2 S, 220,000-dalton polypeptide with the DNA polymerase and 3'- to 5'-exonuclease activities reported for DNA polymerase delta II (Crute, J. J., Wahl, A. F., and Bambara, R. A. (1986) Biochemistry 25, 26-36). Monoclonal antibody to KB cell DNA polymerase alpha, while binding to HeLa DNA polymerase alpha, did not bind to the HeLa DNA polymerase delta. Moreover, at micromolar concentrations N2-(p-n-butylphenyl)-2'-deoxyguanosine 5'-triphosphate (BuPdGTP) and 2-(p-n-butylanilino)-2'-deoxyadenosine 5'-triphosphate (BuAdATP) were potent inhibitors of DNA polymerase alpha, but did not inhibit the DNA polymerase delta. Neither purified DNA polymerase alpha nor beta could promote repair DNA synthesis in the permeabilized cells. Furthermore, under conditions which inhibited purified DNA polymerase alpha by greater than 90%, neither monoclonal antibodies to DNA polymerase alpha, BuPdGTP, nor BuAdATP was able to inhibit significantly the DNA repair synthesis mediated by the DNA polymerase delta. Thus, it appears that a major portion of DNA repair synthesis induced by UV irradiation might be catalyzed by DNA polymerase delta. When xeroderma pigmentosum human diploid fibroblasts were utilized, DNA repair synthesis dependent upon ultraviolet light could be restored by addition of both T4 endonuclease V and DNA polymerase delta, but not by addition of either one alone. This result suggests that cytosol-depleted permeabilized DNA repair-defective human fibroblasts and HeLa DNA polymerase delta might be exploited to provide a functional assay for purifying active DNA repair factors from DNA repair-proficient cells without a preknowledge of their function.
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PMID:DNA repair synthesis in human fibroblasts requires DNA polymerase delta. 333 6

Two intraspecific human cell hybrids, HD2 and HD1A, produced from fusion between HeLa cells and xeroderma pigmentosum fibroblasts, express XPD-like rates of excision repair and hypersensitivity to UV-radiation. In the present paper we describe unusual patterns of UV-induced mutation in both cell lines. Though HD2 very closely resembles XPD both phenotypically and genetically, in UV-dose response it is hypomutable at the loci for ouabain and diphtheria toxin resistance. At equitoxic dose, however, it shows normal mutability, HD1A, by contrast, is hypermutable as a function either of UV dose or in terms of equitoxicity for these genes. HD1A's mutator phenotype is a dominant characteristic and is not associated with grossly abnormal DNA precursor pool imbalance. The possibility remains that DNA polymerase infidelity underlies its hypermutability.
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PMID:Abnormal mutation frequencies in human repair-defective hybrid cell lines. 362 40


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