UMLS:C0043346 - FACTA Search

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Query: UMLS:C0043346 (xeroderma pigmentosum)
2,924 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have assessed the role of cellular transformation in ultraviolet (uv)-induced mutagenic events in human cells. To maintain uniformity of genetic background and to eliminate the effect of DNA repair, primary nontransformed lymphocytes (T-cells) and Epstein-Barr virus-transformed lymphocytes (B-cells) from one patient (XP12Be) with the DNA repair-deficient disorder xeroderma pigmentosum (group A) were transfected with the mutagenesis shuttle vector pZ189. Parallel control experiments were performed with primary, nontransformed lymphocytes from a normal individual and with a repair-proficient Epstein-Barr virus-transformed lymphocyte line (KR6058). pZ189 was treated with uv and introduced into the four cell lines by electroporation. Plasmid survival and mutations inactivating the marker supF suppressor tRNA gene in the recovered pZ189 were scored by transforming an indicator strain of Escherichia coli. Plasmid survival was reduced and mutation frequency elevated equally with both XP-A cell lines compared to both normal cell lines. Base sequence analysis of more than 250 independent plasmids showed that while the G:C----A:T base substitution mutation was found in at least 60% of plasmids with single or tandem mutations with all four cell lines, the frequency with the transformed XP-A (93%) cells was significantly higher (P less than 0.01) than that with the nontransformed XP-A cells (77%). In addition, with the transformed XP-A cells, there were significantly fewer plasmids with transversions and with mutations at a transversion hotspot (base pair 134) than with plasmids recovered from nontransformed XP-A cells. Interleukin-2 and phytohemagglutinin (used to maintain growth of the nontransformed lymphocytes) treatment of transformed XP12Be cells did not change overall plasmid survival or mutation frequency, but increased the transversion frequency and induced a mutational hotspot (at base pair 159), while another mutational hotspot (at base pair 123) disappeared. Thus we have demonstrated that in repair-deficient human cells, cellular transformation, while not affecting overall postuv plasmid survival and mutation frequency, does increase the susceptibility to G:C----A:T transition mutations, a type of mutation associated with uv-induced neoplasia.
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PMID:Ultraviolet mutagenesis in human lymphocytes: the effect of cellular transformation. 132 18

The supF gene of the shuttle vector pZ189 was used as a target for the study of mutations induced by cis-diamminedichloroplatinum(II) (cis-DDP). Normal human repair-proficient fibroblasts and cis-DDP repair-deficient xeroderma pigmentosum (XP) cells were used as host cells to study the effect of cis-DDP on the inhibition of shuttle vector replication and mutagenesis. Transfection of cis-DDP-treated pZ189 into normal and XP cell lines resulted in a marked increase in the mutation frequency and a decrease in the replication efficiency of the vector. However, these effects were much greater for the plasmid propagated in XP cells. Atomic absorption spectroscopy showed that six to eight Pt-DNA adducts per plasmid were necessary to inhibit plasmid replication by 50% in normal cells. In contrast, only one to two Pt-DNA adducts were necessary to inhibit replication of the plasmid by 50% in XP cells. Analysis of mutation sites demonstrated that cis-DDP treatment resulted primarily in single and double mutations separated by one base and limited to a few locations within the 85-bp mature tRNA. Propagation of the cis-DDP-treated vector in either normal or XP cells led to predominantly transversion mutations at AGA, AGG, and GAG sites and a cis-DDP-associated deletion of 174 bp. Although mutations occurred at target sites for cis-DDP adduct formation, there was no correlation between sites of mutation and the most frequent sites of adduct formation.
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PMID:Spectrum of cis-diamminedichloroplatinum(II)-induced mutations in a shuttle vector propagated in human cells. 191 Apr 83

In order to examine possible cell-type specificity in mutagenic events, a shuttle-vector plasmid, pZ189, carrying a bacterial suppressor tRNA marker gene, was treated with ultraviolet radiation and propagated in Epstein-Barr virus transformed lymphoblastoid cell lines from a patient, XP12BE, with xeroderma pigmentosum (XP), group A, and a normal control. XP is a skin-cancer-prone disorder with UV hypersensitivity and defective DNA repair. Plasmid survival and mutations inactivating the marker gene were scored by transforming an indicator strain of E. coli. An earlier report on this data [Seetharam et al., (1990) J. Mol. Biol., 212, 433] indicated lower survival and higher mutation frequency with the UV-treated plasmid passed through the XP12Be(EBV) line. In the present report, sequence analysis of 198 mutant plasmids revealed a predominance of G:C----A:T transitions with both lymphoblastoid cell lines. This finding is consistent with the bias of polymerases toward insertion of an adenine opposite non-coding photoproducts (dinucleotides or other lesions). Transversion mutagenesis, non-adjacent double mutations, and triple-base mutations may involve other mechanisms. These results were compared to similar data from a fibroblast line from the same patient [Bredberg et al., (1986) Proc. Natl. Acad. Sci. (U.S.A.), 83, 8273]. The frequency of G:C----A:T transitions was higher, and there were fewer plasmids with multiple-base substitutions and with transversion mutations with both XP lymphoblasts and fibroblasts than with the normal lymphoblasts and fibroblasts. There were no significant differences in classes or types of mutations in the UV-treated plasmid replicated in the XP lymphoblasts and the XP fibroblasts. This suggests that the major features of UV mutagenesis in different cell types from the same individual are similar.
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PMID:Ultraviolet mutational spectrum in a shuttle vector propagated in xeroderma pigmentosum lymphoblastoid cells and fibroblasts. 198 77

The mutagenesis shuttle vector, pZ189, was treated with ultraviolet (u.v.) radiation in vitro and passed through a DNA repair-deficient lymphoblastoid cell line derived from a patient with xeroderma pigmentosum complementation group A (XP-A) (XP12BE(EBV)) and a DNA repair-proficient lymphoblastoid cell line (GM606(EBV)). After u.v. treatment, plasmid survival was lower and mutation frequency higher with the XP-A cells mirroring the survival and mutagenesis of the host cells. The nature of the mutations in the suppressor tRNA marker gene was determined by direct sequence analysis. The G.C to A.T transition was the dominant (85%) base substitution mutation with the XP lymphoblasts and was the major (56%) base substitution mutation with the repair-proficient lymphoblasts. We found a G.C to A.T transition mutational hotspot with the XP lymphoblasts not seen in our previous experiments with fibroblasts from the same patient. Comparison of the data presented here with our results with DNA repair-deficient and DNA repair-proficient fibroblasts suggests that hotspot variability is not due to genetic polymorphism or repair capacity of the cells. Instead it appears that cellular factors can influence the probability of mutagenesis of modified DNA at particular sites.
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PMID:Mutational hotspot variability in an ultraviolet-treated shuttle vector plasmid propagated in xeroderma pigmentosum and normal human lymphoblasts and fibroblasts. 218 82

A shuttle vector plasmid, pZ189, carrying a bacterial suppressor tRNA marker gene, was treated with ultraviolet radiation and propagated in cultured skin cells from a patient with the skin-cancer-prone, DNA repair-deficient disease xeroderma pigmentosum and in repair-proficient cells. After replication in the human cells, progeny plasmids were purified. Plasmid survival and mutations inactivating the marker gene were scored by transforming an indicator strain of Escherichia coli carrying a suppressible amber mutation in the beta-galactosidase gene. Plasmid survival in the xeroderma pigmentosum cells was less than that of pZ189 harvested from repair-proficient human cells. The point-mutation frequency in the 150-base-pair tRNA marker gene increased up to 100-fold with ultraviolet dose. Sequence analysis of 150 mutant plasmids revealed that mutations were infrequent at potential thymine-thymine dimer sites. Ninety-three percent of the mutant plasmids from the xeroderma pigmentosum cells showed G X C----A X T transitions, compared to 73% in the normal cells (P less than 0.002). There were significantly fewer transversions (P less than 0.002) (especially G X C----T X A) and multiple base substitutions (P less than 0.00001) than when pZ189 was passaged in repair-proficient cells. The subset of mutational changes that are common to ultraviolet-treated plasmids propagated in both repair-proficient and xeroderma pigmentosum skin cells may be associated with the development of ultraviolet-induced skin cancer in humans.
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PMID:Restricted ultraviolet mutational spectrum in a shuttle vector propagated in xeroderma pigmentosum cells. 346 53

Mutagenesis was studied at the DNA-sequence level in human fibroblast and lymphoid cells by use of a shuttle vector plasmid, pZ189, containing a suppressor tRNA marker gene. In a series of experiments, 62 plasmids were recovered that had two to six base substitutions in the 160-base-pair marker gene. Approximately 20-30% of the mutant plasmids that were recovered after passing ultraviolet-treated pZ189 through a repair-proficient human fibroblast line contained these multiple mutations. In contrast, passage of ultraviolet-treated pZ189 through an excision-repair-deficient (xeroderma pigmentosum) line yielded only 2% multiple base substitution mutants. Introducing a single-strand nick in otherwise unmodified pZ189 adjacent to the marker, followed by passage through the xeroderma pigmentosum cells, resulted in about 66% multiple base substitution mutants. The multiple mutations were found in a 160-base-pair region containing the marker gene but were rarely found in an adjacent 170-base-pair region. Passing ultraviolet-treated or nicked pZ189 through a repair-proficient human B-cell line also yielded multiple base substitution mutations in 20-33% of the mutant plasmids. An explanation for these multiple mutations is that they were generated by an error-prone polymerase while filling gaps. These mutations share many of the properties displayed by mutations in the immunoglobulin hypervariable regions.
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PMID:Multiple point mutations in a shuttle vector propagated in human cells: evidence for an error-prone DNA polymerase activity. 347 35

The diagnosis of the melanoma-prone disorder dysplastic nevus syndrome (DNS) is based currently on a combination of clinical and histopathologic examinations of patients. To develop a potential laboratory test for DNS, we utilized the observation that an ultraviolet light (UV)-treated mutagenesis plasmid shuttle vector has an abnormally increased frequency of mutations after transfection into lymphoblastoid cells from a patient with familial DNS. pSP189 (containing the bacterial suppressor tRNA gene supF as a marker for mutations and a gene for ampicillin resistance for selection) was treated with UV and transfected into familial DNS, xeroderma pigmentosum complementation group A (XP-A), and normal lymphoblastoid cells by electroporation or diethylaminoethyl (DEAE) dextran. Untreated plasmid pZ189K (containing a gene for kanamycin resistance) was co-transfected as an internal standard to reduce the variability of plasmid survival measurements. After 2 d, plasmids were extracted, used to transform an indicator strain of Escherichia coli, and assayed on plates containing ampicillin or kanamycin. Counting light blue or white colonies (containing mutated supF in the plasmid) and blue colonies (with wild type supF) permitted measurement of the plasmid survival and mutation frequency. Transfection by electroporation or DEAE dextran resulted in abnormally reduced survival of UV-treated plasmid after passage through the XP-A but normal survival in the three DNS lines. Transfection of UV-treated plasmid by DEAE dextran yielded a greater hypermutability with the familial DNS lines than by electroporation. These results suggest that pSP189 UV hypermutability with normal UV survival using DEAE dextran transfection may form the basis of a potential laboratory assay for familial DNS.
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PMID:A potential laboratory test for dysplastic nevus syndrome: ultraviolet hypermutability of a shuttle vector plasmid. 802 83

Hotspots are a standard feature of mutational spectra induced by mutagens in a variety of marker genes. While it is generally believed that sequence context exerts an important influence on hotspot location, direct experimental evidence is quite limited. We have studied ultraviolet mutagenesis in a suppressor tRNA marker gene (supF) carried in a mammalian shuttle vector and replicated in Xeroderma pigmentosum cells in culture. We have now constructed a small family of functional variant suppressor tRNA marker gene which differ from one another by one or two nucleotide changes. UV mutational spectra were generated for each variant gene. We found that the change of a dipyrimidine from 5' TC to 5' CC eliminated a strong mutational hotspot. In addition a single base change in the supF gene was accompanied by the appearance of a new hotspot eight bases away. Finally, another single base change suppressed a major hotspot 48 bases away. Polymerase stop assays on the UV modified marker genes were used to measure the frequency and distribution of photoproducts. The differences in hotspot patterns could not be explained by differences in modification patterns. These results indicate that a change in sequence context can directly influence the probability of mutagenesis at specific sites.
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PMID:Proximal and distal effects of sequence context on ultraviolet mutational hotspots in a shuttle vector replicated in xeroderma cells. 810 35

Shuttle vector plasmids pYZ289 were irradiated with UV and transfected to mouse cells to permit repair of damage, mutation and replication in the cells. The frequency and types of mutations were compared with those of UV-irradiated shuttle vector plasmids pZ189 which were propagated in normal human and xeroderma pigmentosum (XP) patient cells defective in DNA repair. Both shuttle vector plasmids contain a bacterial suppressor tRNA gene supF as a common mutation target. pYZ289 propagated in the mouse cells showed survival and mutation frequency similar to pZ189 propagated in the normal human cells. All single base substitution mutations were induced in dipyrimidine sequences and G:C to A:T transition was most frequently observed (47%) in the mouse cells; however, the frequency was significantly lower than that in the XP cells. The frequency of the base substitution mutations at A:T base pairs was significantly higher in the mouse cells (29%) than in the normal human (12%) and the XP cells (6%). These results show that similar types of mutations are induced by UV in mouse and normal human cells, and that the A:T base pair is relatively more mutable in mouse than in normal human and XP cells.
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PMID:Similarity in the molecular profile of mutations induced by UV light in shuttle vector plasmids propagated in mouse and human cells. 820 34

Trichothiodystrophy (TTD) is a rare genetic disease associated in approximately 50% of patients with DNA repair deficiency analogous to that found in xeroderma pigmentosum group D (XP-D) patients. Although XP-D patients exhibit a very high level of skin cancer on sun-exposed parts, TTD is not associated with cancer. We analysed UV-induced mutations in TTD cells and compared them to data in XP-D in order to determine if the molecular mechanisms of mutagenesis can explain the discrepancies between these two syndromes. We first immortalized a fibroblast TTD line with an ori(-)-SV40 plasmid. To investigate the kinds of mutations induced in TTD cells, we used an UV-irradiated (at 254 nm) shuttle vector carrying the supF tRNA gene as a target. We compared our data with those published by others with the same pZ189 vector in normal and XP-D fibroblast lines (Bredberg et al., Proc. Natl. Acad. Sci. USA, 83, 8273-8277; Seetharam et al., J. Clin. Invest., 80, 1613-1617). The frequency of mutants increased linearly with UV dose and the slope was > 4 times steeper in TTD cells than that observed in normal cells. The mutation frequency was almost identical between XP-D and TTD cells. Sequence analysis of the supF tRNA gene showed that 96% of mutations obtained in TTD cells are base substitutions. Single base substitutions were found in 62% of mutants in TTD cells while they corresponded to 86% in XP-D cells. The frequency of multiple mutations in TTD cells (26%) was similar to that in normal cells (27%) and much higher than that in XP-D cells (9%). Despite the fact that the same gene is mutated in TTD and XP patients, the molecular characteristics of mutagenesis are not identical. The fact that the frequency of mutations in TTD and XP cells are similar shows that a high level of UV-induced mutations is therefore not always directly related to cancer-proneness. Other factors such as catalase activity and immuno-surveillance may intervene in cancer incidence.
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PMID:UV-induced mutations in a shuttle vector replicated in repair deficient trichothiodystrophy cells differ with those in genetically-related cancer prone xeroderma pigmentosum. 839 42

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