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Fleck SC, Sauter F, Pfeiffer E, Metzler M, Hartwig A, Köberle B. DNA damage and repair kinetics of the Alternaria mycotoxins alternariol, altertoxin II and stemphyltoxin III in cultured cells. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2016; 798-799:27-34. [DOI: 10.1016/j.mrgentox.2016.02.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Revised: 02/04/2016] [Accepted: 02/05/2016] [Indexed: 12/18/2022]
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2
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Sassa A, Kamoshita N, Kanemaru Y, Honma M, Yasui M. Xeroderma Pigmentosum Group A Suppresses Mutagenesis Caused by Clustered Oxidative DNA Adducts in the Human Genome. PLoS One 2015; 10:e0142218. [PMID: 26559182 PMCID: PMC4641734 DOI: 10.1371/journal.pone.0142218] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Accepted: 10/19/2015] [Indexed: 12/27/2022] Open
Abstract
Clustered DNA damage is defined as multiple sites of DNA damage within one or two helical turns of the duplex DNA. This complex damage is often formed by exposure of the genome to ionizing radiation and is difficult to repair. The mutagenic potential and repair mechanisms of clustered DNA damage in human cells remain to be elucidated. In this study, we investigated the involvement of nucleotide excision repair (NER) in clustered oxidative DNA adducts. To identify the in vivo protective roles of NER, we established a human cell line lacking the NER gene xeroderma pigmentosum group A (XPA). XPA knockout (KO) cells were generated from TSCER122 cells derived from the human lymphoblastoid TK6 cell line. To analyze the mutagenic events in DNA adducts in vivo, we previously employed a system of tracing DNA adducts in the targeted mutagenesis (TATAM), in which DNA adducts were site-specifically introduced into intron 4 of thymidine kinase genes. Using the TATAM system, one or two tandem 7,8-dihydro-8-oxoguanine (8-oxoG) adducts were introduced into the genomes of TSCER122 or XPA KO cells. In XPA KO cells, the proportion of mutants induced by a single 8-oxoG (7.6%) was comparable with that in TSCER122 cells (8.1%). In contrast, the lack of XPA significantly enhanced the mutant proportion of tandem 8-oxoG in the transcribed strand (12%) compared with that in TSCER122 cells (7.4%) but not in the non-transcribed strand (12% and 11% in XPA KO and TSCER122 cells, respectively). By sequencing the tandem 8-oxoG-integrated loci in the transcribed strand, we found that the proportion of tandem mutations was markedly increased in XPA KO cells. These results indicate that NER is involved in repairing clustered DNA adducts in the transcribed strand in vivo.
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Affiliation(s)
- Akira Sassa
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, Setagaya-ku, Tokyo, Japan
- * E-mail: (MY); (AS)
| | - Nagisa Kamoshita
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, Setagaya-ku, Tokyo, Japan
| | - Yuki Kanemaru
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, Setagaya-ku, Tokyo, Japan
| | - Masamitsu Honma
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, Setagaya-ku, Tokyo, Japan
| | - Manabu Yasui
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, Setagaya-ku, Tokyo, Japan
- * E-mail: (MY); (AS)
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3
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Camenisch U, Nägeli H. XPA gene, its product and biological roles. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 637:28-38. [PMID: 19181108 DOI: 10.1007/978-0-387-09599-8_4] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The 31 kDa XPA protein is part of the core incision complex of the mammalian nucleotide excision repair (NER) system and interacts with DNA as well as with many other NER subunits. In the absence of XPA, no incision complex can form and no excision of damaged DNA damage occurs. A comparative analysis of the DNA-binding properties in the presence of different substrate conformations indicated that XPA protein interacts preferentially with kinked DNA backbones. The DNA-binding domain of XPA protein displays a positively charged deft that is involved in an indirect readout mechanism, presumably by detecting the increased negative potential encountered at sharp DNA bends. We propose that this indirect recognition function contributes to damage verification by probing the susceptibility of the DNA substrate to be kinked during the assembly of NER complexes.
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Affiliation(s)
- Ulrike Camenisch
- Institute of Pharmacology and Toxicology, University of Zürich-Vetsuisse, Zürich, Switzerland.
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Adair JE, Maloney SC, Dement GA, Wertzler KJ, Smerdon MJ, Reeves R. High-mobility group A1 proteins inhibit expression of nucleotide excision repair factor xeroderma pigmentosum group A. Cancer Res 2007; 67:6044-52. [PMID: 17616660 DOI: 10.1158/0008-5472.can-06-1689] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cells that overexpress high-mobility group A1 (HMGA1) proteins exhibit deficient nucleotide excision repair (NER) after exposure to DNA-damaging agents, a condition ameliorated by artificially lowering intracellular levels of these nonhistone proteins. One possible mechanism for this NER inhibition is down-regulation of proteins involved in NER, such as xeroderma pigmentosum complimentation group A (XPA). Microarray and reverse transcription-PCR data indicate a 2.6-fold decrease in intracellular XPA mRNA in transgenic MCF-7 cells overexpressing HMGA1 proteins compared with non-HMGA1-expressing cells. XPA protein levels are also approximately 3-fold lower in HMGA1-expressing MCF-7 cells. Moreover, whereas a >2-fold induction of XPA proteins is observed in normal MCF-7 cells 30 min after UV exposure, no apparent induction of XPA protein is observed in MCF-7 cells expressing HMGA1. Mechanistically, we present both chromatin immunoprecipitation and promoter site-specific mutagenesis evidence linking HMGA1 to repression of XPA transcription via binding to a negative regulatory element in the endogenous XPA gene promoter. Phenotypically, HMGA1-expressing cells exhibit compromised removal of cyclobutane pyrimidine dimer lesions, a characteristic of cells that express low levels of XPA. Importantly, we show that restoring expression of wild-type XPA in HMGA1-expressing cells rescues UV resistance comparable with that of normal MCF-7 cells. Together, these data provide strong experimental evidence that HMGA1 proteins are involved in inhibiting XPA expression, resulting in increased UV sensitivity in cells that overexpress these proteins. Because HMGA1 proteins are overexpressed in most naturally occurring cancers, with increasing cellular concentrations correlating with increasing metastatic potential and poor patient prognosis, the current findings provide new insights into previously unsuspected mechanisms contributing to tumor progression.
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Affiliation(s)
- Jennifer E Adair
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, USA
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Maltseva EA, Rechkunova NI, Gillet LC, Petruseva IO, Schärer OD, Lavrik OI. Crosslinking of the NER damage recognition proteins XPC-HR23B, XPA and RPA to photoreactive probes that mimic DNA damages. Biochim Biophys Acta Gen Subj 2007; 1770:781-9. [PMID: 17320292 DOI: 10.1016/j.bbagen.2007.01.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Revised: 01/12/2007] [Accepted: 01/16/2007] [Indexed: 12/31/2022]
Abstract
A new assay to probe the mechanism of mammalian nucleotide excision repair (NER) was developed. Photoreactive arylazido analogues of dNMP in DNA were shown to be substrates for the human NER system. Oligonucleotides carrying photoreactive "damages" were prepared using the multi-stage protocol including one-nucleotide gap filling by DNA polymerase beta using photoreactive dCTP or dUTP analogues followed by ligation of the resulting nick. Photoreactive 60-mers were annealed with single-stranded pBluescript II SK (+) and subsequently primer extension reactions were performed. Incubation of HeLa extracts with the plasmids containing photoreactive moieties resulted in an excision pattern typical of NER. DNA duplexes containing photoreactive analogues were used to analyze the interaction of XPC-HR23B, RPA, and XPA with damaged DNA using the photocrosslinking assay. Crosslinking of the XPC-HR23B complex with photoreactive 60-mers resulted in modification of its XPC subunit. RPA crosslinked to ssDNA or mismatched dsDNA more efficiently than to dsDNA, whereas XPA did not show a preference for any of the DNA species. XPC and XPA photocrosslinking to DNA decreased in the presence of Mg(2+) whereas RPA crosslinking to DNA was not sensitive to this cofactor. Our data establish a photocrosslinking assay for the investigation of the damage recognition step in human nucleotide excision repair.
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Affiliation(s)
- Ekaterina A Maltseva
- Institute of Chemical Biology and Fundamental Medicine, Lavrentiev av. 8, 630090 Novosibirsk, Russia
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6
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Hochberg M, Kohen R, Enk CD. Role of antioxidants in prevention of pyrimidine dimer formation in UVB irradiated human HaCaT keratinocytes. Biomed Pharmacother 2006; 60:233-7. [PMID: 16765564 DOI: 10.1016/j.biopha.2006.04.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2006] [Accepted: 04/11/2006] [Indexed: 11/20/2022] Open
Abstract
The objective of the present study was to study the role of reactive oxygen species (ROS) in UVB induced cyclobutane pyrimidine dimer (CPD) formation in human keratinocytes, and to examine the modulating activity of low molecular weight antioxidants. To demonstrate the involvement of ROS, we examined the protective capacity of alpha-tocopherol, tempamine, and diethyldithiocarbamate (DDC) on CPD formation in intact cells and naked DNA. HaCaT cells and naked DNA in water solution were irradiated with UVB in the presence of the antioxidants and CPD was determined by ELISA. We found that all three antioxidants provided protection against UVB induced CPD formation. The protection was observed in intact cells only and not in naked DNA. Since some of the tested antioxidants do not possess UV absorbing qualities, our findings suggest that in a cellular environment ROS play a role in CPD formation.
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Affiliation(s)
- Malka Hochberg
- Department of Dermatology, Hadassah Medical Center, Hebrew University, Jerusalem, Israel
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Köberle B, Roginskaya V, Wood RD. XPA protein as a limiting factor for nucleotide excision repair and UV sensitivity in human cells. DNA Repair (Amst) 2006; 5:641-8. [PMID: 16413230 DOI: 10.1016/j.dnarep.2005.12.001] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2005] [Revised: 11/28/2005] [Accepted: 12/05/2005] [Indexed: 01/06/2023]
Abstract
Nucleotide excision repair (NER) acts on a variety of DNA lesions, including damage induced by many chemotherapeutic drugs. Cancer therapy with such drugs might be improved by reducing the NER capacity of tumors. It is not known, however to what extent any individual NER protein is rate-limiting for any step of the repair reaction. We studied sensitivity to UV radiation and repair of DNA damage with regard to XPA, one of the core factors in the NER incision complex. About 150,000-200,000 molecules of XPA protein are present in NER proficient human cell lines, and no XPA protein in the XP-A cell line XP12RO. Transfected XP12RO cell lines expressing 50,000 or more XPA molecules/cell showed UV resistance similar to normal cells. Suppression of XPA protein to approximately 10,000 molecules/cell in a Tet-regulatable system modestly but significantly increased sensitivity to UV irradiation. No removal of cyclobutane pyrimidine dimers was detected in the SV40 immortalized cell lines tested. Repair proficient WI38-VA fibroblasts and transfected XP-A cells expressing 150,000 molecules of XPA/cell removed (6-4) photoproducts from the genome with a half-life of 1h. Cells in which XPA protein was reduced to about 10,000 molecules/cell removed (6-4) photoproducts more slowly, with a half-life of 3h. A reduced rate of repair of (6-4) photoproducts thus results in increased cellular sensitivity towards UV irradiation. These data indicate that XPA levels must be reduced to <10% of that present in a normal cell to render XPA a limiting factor for NER and consequent cellular sensitivity. To inhibit NER, it may be more effective to interfere with XPA protein function, rather than reducing XPA protein levels.
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Affiliation(s)
- Beate Köberle
- UPCI and Department of Pharmacology, University of Pittsburgh, Hillman Cancer Center, Research Pavilion, Suite 2.6, 5117 Centre Avenue, Pittsburgh, PA 15213-1863, USA.
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8
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Reddy AP, Bethea CL. Preliminary array analysis reveals novel genes regulated by ovarian steroids in the monkey raphe region. Psychopharmacology (Berl) 2005; 180:125-40. [PMID: 15731897 DOI: 10.1007/s00213-005-2154-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2004] [Accepted: 11/30/2004] [Indexed: 10/25/2022]
Abstract
We hypothesize that ovarian hormones may improve serotonin neuron survival. We sought the effect of estradiol (E) and progesterone (P) on novel gene expression in the macaque dorsal raphe region with Affymetrix array analysis. Nine spayed rhesus macaques were treated with either placebo, E or E+P via Silastic implant for 1 month prior to euthanasia (n=3 per treatment). RNA was extracted from a small block of midbrain containing the dorsal raphe and examined on an Agilent Bioanalyzer. The RNA from each monkey was labeled and hybridized to an Affymetrix HG_U95AV Human GeneChip Array. After filtering and sorting, 25 named genes remained that were regulated by E, and 24 named genes remained that were regulated by supplemental P. These genes further sorted into functional categories that would promote neuronal plasticity, transmitter synthesis, and trafficking, as well as reduce apoptosis. The relative abundance of four pivotal genes was examined in all nine animals with quantitative RT-PCR and normalized by glyceraldehyde 3-phosphate dehydrogenase (GAPDH). E+/-P caused a significant threefold reduction in JNK-1 (a pro-apoptosis gene, p<0.007); and a significant sixfold decrease in kynurenine mono-oxygenase (produces neurotoxic quinolones, p<0.05). GABA-A receptor (alpha3 subunit; benzodiazepine site) and E2F1 (interferes with cytokine signaling) were unaffected by E, but increased sevenfold (p<0.02) and fourfold (p<0.009), respectively, upon treatment with P. In summary, subsets of genes related to tissue remodeling or apoptosis were up- or down-regulated by E and P in a tissue block containing the dorsal raphe. These changes could promote cellular resilience in the region where serotonin neurons originate.
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Affiliation(s)
- Arubala P Reddy
- Division of Reproductive Sciences, Oregon National Primate Research Center, Beaverton, OR 97006, USA
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Porter PC, Mellon I, States JC. XP-A cells complemented with Arg228Gln and Val234Leu polymorphic XPA alleles repair BPDE-induced DNA damage better than cells complemented with the wild type allele. DNA Repair (Amst) 2005; 4:341-9. [PMID: 15661657 DOI: 10.1016/j.dnarep.2004.10.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2004] [Accepted: 10/18/2004] [Indexed: 11/25/2022]
Abstract
Functional effects of Arg228Gln and Val2343Leu XPA polymorphisms on benzo[a]pyrene-r-7,t-8-dihydrodiol-t-9,10-epoxide-(+/-)-anti (BPDE) survival and repair were investigated in SV40 immortalized XP12RO cells complemented with wild type and polymorphic XPA cDNAs in an inducible cDNA expression system. In contrast to previous studies showing little impact of XPA polymorphisms on UV survival and repair, cells complemented with polymorphic XPAs displayed improved BPDE survival and repair as compared to wild type XPA-complemented cells. Survival after BPDE treatment was measured using AlamarBlue reduction and colony forming ability. Cells expressing low levels of either polymorphic XPA had equivalent or improved survival compared to wild type XPA-complemented cells (XPAwt cells). XPA induction improved BPDE survival in Arg228Gln (R228Q cells) and Val234Leu (V234L cells) complemented cells, but not XPAwt cells. BPDE-induced DNA damage repair was measured both by reactivation after transfection of a luciferase reporter plasmid reacted with BPDE in vitro, and by removal of adducts from genomic DNA of BPDE-treated cells. BPDE-induced DNA damage repair in R228Q and V234L cells expressing XPA at very low levels was similar to repair in XPAwt cells expressing XPA at normal levels. XPA induction improved repair in R228Q and V234L cells but not in XPAwt cells. Our findings suggest that both Arg228Gln and Val234Leu XPAs function better than wild type XPA for BPDE adduct removal. These observations differ from UV repair results suggesting that the differences are lesion specific. The location of the polymorphisms within the putative poly(ADP-ribose) binding domain suggests that poly(ADP-ribose) interaction is important in repair.
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Affiliation(s)
- Paul C Porter
- Department of Pharmacology and Toxicology, Center for Genetics and Molecular Medicine, James Graham Brown Cancer Center, and Center for Environmental and Occupational Health Sciences, University of Louisville, Louisville, KY 40202, USA
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10
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Terunuma A, Ye J, Emmert S, Khan SG, Kraemer KH, Vogel JC. Ultraviolet light selection assay to optimize oligonucleotide correction of mutations in endogenous xeroderma pigmentosum genes. Gene Ther 2005; 11:1729-34. [PMID: 15334113 DOI: 10.1038/sj.gt.3302344] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Various oligonucleotide (ODN)-based approaches have been proposed for their ability to correct mutated genes at the normal chromosomal locations. However, the reported gene correction frequencies of these approaches have varied markedly in different experimental settings, including when different tissues or cell types are targeted. In order to find the optimal ODN-based approach for a specific target tissue, an assay system that allows direct comparison of the different methods on that tissue is necessary. Herein, we describe an XP-UVC selection assay that can be used to evaluate and compare gene correction frequencies in different cell types obtained from a xeroderma pigmentosum (XP) patient, following treatment by different ODN-based approaches. As an experimental example, the XP-UVC selection assay was used to assess the ability of chimeric RNA/DNA ODN to correct point mutations in the XPA gene. This assay can be used to assess and evaluate other types of ODN-based approaches, and to further optimize them.
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Affiliation(s)
- A Terunuma
- Dermatology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
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11
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States JC, McDuffie ER, Myrand SP, McDowell M, Cleaver JE. Distribution of mutations in the human xeroderma pigmentosum group A gene and their relationships to the functional regions of the DNA damage recognition protein. Hum Mutat 2000; 12:103-13. [PMID: 9671271 DOI: 10.1002/(sici)1098-1004(1998)12:2<103::aid-humu5>3.0.co;2-6] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A series of xeroderma pigmentosum group A cell lines from 19 patients and cell lines from 13 other family members were examined for XPA mutations to find previously unidentified mutations from American and European patients, to establish pedigrees in represented families, and to develop a database for XPA diagnosis. Most mutations were deletions and splice site mutations observed previously in other XPA patients, in exon III, intron III, or exon IV, that resulted in frameshifts within the DNA binding region-including an Afl III RFLP (G to C) in four unrelated families. One new mutation was a point mutation within intron III (A to G) creating a new splice acceptor site that may compete with the original splice acceptor site. Missplicing at this new site inserts 11 nucleotides in the mRNA creating a frameshift. A small amount of normal splicing to give wild-type XPA protein is the likely molecular mechanism for the relatively mild clinical features of this patient. In another patient, a new 2 bp deletion in the RPA70 binding region was identified in the same region as a 20 bp deletion previously characterized in an unrelated patient. Mutations in the DNA binding region of XPA were from patients with the more severe disease often associated with neurological complications, whereas mutations in the C-terminal end of the protein, which interacts with the TFIIH transcription factor, were from patients with milder skin disease only. The rarity of naturally occurring missense mutations in the DNA binding region of XPA suggests that amino acid changes might be sufficiently tolerated that patients would have mild symptoms and escape detection.
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Affiliation(s)
- J C States
- Center for Molecular Medicine and Genetics, Wayne State University, Detroit, MI, USA
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12
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Cleaver JE, Thompson LH, Richardson AS, States JC. A summary of mutations in the UV-sensitive disorders: xeroderma pigmentosum, Cockayne syndrome, and trichothiodystrophy. Hum Mutat 2000; 14:9-22. [PMID: 10447254 DOI: 10.1002/(sici)1098-1004(1999)14:1<9::aid-humu2>3.0.co;2-6] [Citation(s) in RCA: 177] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The human diseases xeroderma pigmentosum, Cockayne syndrome, and trichothiodystrophy are caused by mutations in a set of interacting gene products, which carry out the process of nucleotide excision repair. The majority of the genes have now been cloned and many mutations in the genes identified. The relationships between the distribution of mutations in the genes and the clinical presentations can be used for diagnosis and for understanding the functions and the modes of interaction among the gene products. The summary presented here represents currently known mutations that can be used as the basis for future studies of the structure, function, and biochemical properties of the proteins involved in this set of complex disorders, and may allow determination of the critical sites for mutations leading to different clinical manifestations. The summary indicates where more data are needed for some complementation groups that have few reported mutations, and for the groups for which the gene(s) are not yet cloned. These include the Xeroderma pigmentosum (XP) variant, the trichothiodystrophy group A (TTDA), and ultraviolet sensitive syndrome (UVs) groups. We also recommend that the XP-group E should be defined explicitly through molecular terms, because assignment by complementation in culture has been difficult. XP-E by this definition contains only those cell lines and patients that have mutations in the small subunit, DDB2, of a damage-specific DNA binding protein.
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Affiliation(s)
- J E Cleaver
- UCSF Cancer Center and Department of Dermatology, University of California, San Francisco 94143-0808, USA.
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Panchal RG, Wang S, McDermott J, Link CJ. Partial functional correction of xeroderma pigmentosum group A cells by suppressor tRNA. Hum Gene Ther 1999; 10:2209-19. [PMID: 10498252 DOI: 10.1089/10430349950017194] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Genetic diseases are often caused by nonsense mutations. The resulting defect in protein translation can be restored by expressing suppressor tRNA in the mutant cells. Our goal was to demonstrate both protein restoration and phenotypic correction using these small transgenes. Functional activity of an arginine opal suppressor tRNA in cells expressing a nonsense mutated GFP gene was demonstrated by restored fluorescence. This suppressor tRNA was expressed in xeroderma pigmentosum group A cells, containing a homozygous nonsense mutation at Arg-207 in the XPA complementing gene. The transfected XPA cell population showed a twofold increase in cell survival after UV irradiation as determined by colony-forming assays compared with cell populations without the suppressor tRNA gene. The UV doses required for 37% survival of XP cells and XP cells expressing the suppressor tRNA were 0.6 and 1.2 J/m2. A similar twofold increase in the reactivation of UV-irradiated plasmid DNA was observed in XP cells expressing the suppressor tRNA. However, there was no detectable increase in XPA protein levels. Several potential limitations of this approach exist, including the availability of mutant RNA transcripts, the efficiency of suppression by the suppressor tRNA, and the abundance and availability and continued expression of the suppressor tRNA. The unique feature of this study is the relatively small size (88 bp) of the suppressor tRNA. Small-sized suppressor tRNAs can be synthetically constructed and subcloned into different viral vectors for delivery into the target cells. This approach may be useful for other genetic diseases caused by nonsense mutations.
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Affiliation(s)
- R G Panchal
- Human Gene Therapy Research Institute, Des Moines, IA 50309, USA
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Maeda T, Eller MS, Hedayati M, Grossman L, Gilchrest BA. Enhanced repair of benzo(a)pyrene-induced DNA damage in human cells treated with thymidine dinucleotides. Mutat Res 1999; 433:137-45. [PMID: 10102040 DOI: 10.1016/s0921-8777(98)00071-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The small DNA fragment thymidine dinucleotide (pTpT) stimulates photoprotective responses in mammalian cells and intact skin. These responses include increased melanogenesis (tanning) and enhanced repair of DNA damage induced by ultraviolet (UV) light. Here we show that pTpT treatment of human keratinocytes enhances their repair of DNA damaged by the chemical carcinogen benzo(a)pyrene (BP), as determined by increased expression of a transfected BP-damaged reporter plasmid containing the chloramphenicol acetyltransferase (CAT) gene. The pTpT-enhanced repair of this BP-damaged plasmid is accomplished at least in part through activation of the p53 tumor suppressor protein and transcription factor, because p53-null H1299 cells showed enhanced repair only if previously transfected with a p53-expression vector. To elucidate the mechanism of this enhanced DNA repair, we examined the expression of p21 and proliferating cell nuclear antigen (PCNA), proteins known to be regulated by p53, as well as the XPA protein, which is mutated in the inherited repair-deficient disorder xeroderma pigmentosum (XP) group A and is necessary for the recognition of UV-induced DNA photoproducts. The p53, PCNA and XPA proteins were all up-regulated within 48 h after the addition of pTpT. Taken together, these data demonstrate that pTpT-enhanced repair of DNA damaged by either UV irradiation or chemical mutagens can be achieved in human cells by exposure to small DNA fragments at least in part through the activation of p53 and increased expression of p53-regulated genes.
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Affiliation(s)
- T Maeda
- Department of Dermatology, Boston University School of Medicine, MA 02118-2394, USA
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15
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Sumitani S, Ishikawa Y, Ishikawa Y, Minami R. Molecular studies of Japanese patients with group A xeroderma pigmentosum using polymerase chain reaction and restriction fragment length polymorphism and nonradioactive single strand conformation polymorphism analyses. J Child Neurol 1999; 14:168-72. [PMID: 10190268 DOI: 10.1177/088307389901400307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Xeroderma pigmentosum is an autosomal recessive disease characterized by extreme sensitivity of the skin to ultraviolet light, which results in a high incidence of early skin cancer. We report here the molecular analysis of the xeroderma pigmentosum group A complementing genes of five Japanese patients with group A xeroderma pigmentosum and their families, by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis, and by PCR and non-radioactive single strand conformation polymorphism (SSCP) analysis using the Pharmacia PhastSystem. Four of the five patients were found to be homozygous for a known splicing mutation of intron 3. One patient was found to be heterozygous for the splicing mutation of intron 3 and a known nonsense mutation of exon 6. This nonradioactive PCR-SSCP technique was as useful for the molecular diagnosis of patients with group A xeroderma pigmentosum as was PCR-RFLP analysis.
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Affiliation(s)
- S Sumitani
- Department of Pediatrics, National Yakumo Hospital, Hokkaido, Japan
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16
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Ikegami T, Kuraoka I, Saijo M, Kodo N, Kyogoku Y, Morikawa K, Tanaka K, Shirakawa M. Solution structure of the DNA- and RPA-binding domain of the human repair factor XPA. NATURE STRUCTURAL BIOLOGY 1998; 5:701-6. [PMID: 9699634 DOI: 10.1038/1400] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The solution structure of the central domain of the human nucleotide excision repair protein XPA, which binds to damaged DNA and replication protein A (RPA), was determined by nuclear magnetic resonance (NMR) spectroscopy. The central domain consists of a zinc-containing subdomain and a C-terminal subdomain. The zinc-containing subdomain has a compact globular structure and is distinct from the zinc-fingers found in transcription factors. The C-terminal subdomain folds into a novel alpha/beta structure with a positively charged superficial cleft. From the NMR spectra of the complexes, DNA and RPA binding surfaces are suggested.
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Affiliation(s)
- T Ikegami
- Graduate School of Biological Sciences, Nara Institute of Sciences and Technology, Ikoma, Japan
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States JC, McDuffie ER, Myrand SP, McDowell M, Cleaver JE. Distribution of mutations in the human xeroderma pigmentosum group A gene and their relationships to the functional regions of the DNA damage recognition protein. Hum Mutat 1998. [DOI: 10.1002/(sici)1098-1004(1998)12:2%3c103::aid-humu5%3e3.0.co;2-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Cleaver JE, States JC. The DNA damage-recognition problem in human and other eukaryotic cells: the XPA damage binding protein. Biochem J 1997; 328 ( Pt 1):1-12. [PMID: 9359827 PMCID: PMC1218880 DOI: 10.1042/bj3280001] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The capacity of human and other eukaryotic cells to recognize a disparate variety of damaged sites in DNA, and selectively excise and repair them, resides in a deceptively small simple protein, a 38-42 kDa zinc-finger binding protein, XPA (xeroderma pigmentosum group A), that has no inherent catalytic properties. One key to its damage-recognition ability resides in a DNA-binding domain which combines a zinc finger and a single-strand binding region which may infiltrate small single-stranded regions caused by helix-destabilizing lesions. Another is the augmentation of its binding capacity by interactions with other single-stranded binding proteins and helicases which co-operate in the binding and are unloaded at the binding site to facilitate further unwinding of the DNA and subsequent catalysis. The properties of these reactions suggest there must be considerable conformational changes in XPA and associated proteins to provide a flexible fit to a wide variety of damaged structures in the DNA.
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Affiliation(s)
- J E Cleaver
- Laboratory of Radiobiology and Environmental Health, University of California, San Francisco 94143-0750, USA
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Chadwick BP, Obermayr F, Frischauf AM. FKHL15, a new human member of the forkhead gene family located on chromosome 9q22. Genomics 1997; 41:390-6. [PMID: 9169137 DOI: 10.1006/geno.1997.4692] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
FKHL15 was isolated from a cDNA library enriched for transcripts from 9q22. Isolation and sequencing of a 3.5-kb cDNA clone identified a putative 376-amino-acid protein with greater than 80% homology over a 100-amino-acid stretch to the forkhead DNA-binding domain. The FKHL15 gene contains a region rich in alanine residues, frequently associated with transcriptional repression. The forkhead genes are believed to play important roles in development and differentiation in many different organisms and have also been implicated in the development of some tumors. The map position of FKHL15 on 9q22 places the gene within the candidate regions for the cancer predisposition syndrome multiple self-healing squamous epitheliomata and the degenerative neurological disorder hereditary sensory neuropathy type I. This is a region frequently lost in squamous cell cancer.
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Affiliation(s)
- B P Chadwick
- Imperial Cancer Research Fund, London, United Kingdom
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States JC, Reed E. Enhanced XPA mRNA levels in cisplatin-resistant human ovarian cancer are not associated with XPA mutations or gene amplification. Cancer Lett 1996; 108:233-7. [PMID: 8973600 DOI: 10.1016/s0304-3835(96)04428-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Enhanced expression of the nucleotide excision repair gene XPA is associated with resistance to cisplatin treatment in human ovarian cancer. Understanding the cause of enhanced XPA expression will provide new molecular targets for therapy directed at overcoming chemoresistance. Enhanced gene expression in cancer cells is often caused by mutations or gene amplification. Molecular analyses of the XPA genes in human ovarian cancers indicate that gene mutation and amplification are not the cause of enhanced XPA mRNA levels in ovarian cancers overexpressing XPA. Altered nucleotide excision repair (NER) gene regulation in chemoresistant tumors is discussed.
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Affiliation(s)
- J C States
- Center for Molecular Medicine and Genetics, Wayne State University, Detroit, MI,
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Abstract
We cloned the human xeroderma pigmentosum group A gene (XPA) and characterized the XPA promoter (pXPA) by transient cat expression. The pXPA is extraordinarily weak in human fibroblasts (1% of RSV-LTR) and appears to function without any of the usual promoter elements. Regions containing positive and negative control elements were localized.
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Affiliation(s)
- R S Topping
- Center for Molecular Medicine and Genetics, Wayne State University, Detroit, MI 48201, USA
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Cleaver JE, McDowell M, Jones C, Wood R, Karentz D. Mutation and expression of the XPA gene in revertants and hybrids of a xeroderma pigmentosum cell line. SOMATIC CELL AND MOLECULAR GENETICS 1994; 20:327-37. [PMID: 7974007 DOI: 10.1007/bf02254721] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A series of ultraviolet (UV)-resistant cell lines have been generated from a UV-sensitive XP group A cell line homozygous for a stop codon (TGA) in the chromosome 9 XPA gene. Three lines generated by chemical mutagenesis acquired the ability to excise (6-4) photoproducts but not cyclobutane dimers from the whole genome; two lines generated by a fusion procedure with hamster cells acquired the ability to excise both (6-4) photoproducts and cyclobutane dimers from the whole genome. A central region of the hamster XPA gene was cloned and sequenced. With the use of species-specific primers in the polymerase chain reaction, we found that the hybrid cell lines do not contain a hamster XPA gene. Sequence analysis showed that all of the UV-resistant cell lines contain reversions of the human stop codon, resulting in missense mutations (glycine or leucine for arginine) or wild-type sequences. The concentration of XPA protein in revertant cell lines was about one-half that in normal cells, which would be expected from heterozygous cells; there was no evidence that the mutant proteins were less stable than the wild-type proteins. These results are consistent with the idea that the XPA protein initiates repair by binding to damaged sites with various affinities, depending on the photoproduct and the transcriptional state of the region. A concentration of XPA protein near 50% is needed before repair can proceed into nontranscribed regions of the genome. The revertant cell lines represent a class of missense mutations in the XPA gene that may have altered specificity and that can be used to understand some of the regulatory differences in repair of photoproducts in various regions of the genome.
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Affiliation(s)
- J E Cleaver
- Laboratory of Radiobiology and Environmental Health, University of California, San Francisco 94143-0750
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