Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.7 (DNA polymerase)
 17,007 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

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

During nucleotide excision repair, damaged DNA is incised on both sides of a lesion and an oligomer containing the damage is excised and replaced by repair DNA synthesis. The latter step is accomplished in vitro by proteins that include the DNA polymerase accessory factor PCNA, which binds to DNA ends to initiate repair synthesis. An increased association of PCNA with nuclei occurs after UV irradiation of nonreplicating DNA in normal human fibroblasts, probably following incision of damaged DNA. This property was used to detect the catalysis of nucleotide excision repair incisions in damaged DNA in vivo, by immunostaining of quiescent human fibroblasts with the widely available PC10 antibody. We summarize here a comprehensive survey of PCNA immunostaining in repair-defective xeroderma pigmentosum (XP) cells in comparison to normal cells. XP-A and XP-G cells were completely defective in staining for PCNA 30 min after UV irradiation. This strongly suggests that XPA and XPG proteins are absolutely required in cells before any incisions can be formed in damaged DNA. XP-B, XP-C, XP-D, and XP-F cells showed an intermediate level of staining for PCNA after UV irradiation, indicative of partial incision capacity in those cells. UV-irradiated XP-E and XP-V cells showed normal PCNA immunostaining levels, consistent with evidence that the corresponding factors are not essential for the incision step of repair. The results provide further evidence for the involvement of PCNA in the repair process in vivo and give an alternative to traditional approaches for measurement of nucleotide excision repair capability.
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PMID:Detection of nucleotide excision repair incisions in human fibroblasts by immunostaining for PCNA. 749 31

Nucleotide excision repair is the principal way by which human cells remove UV damage from DNA. Human cell extracts were fractionated to locate active components, including xeroderma pigmentosum (XP) and ERCC factors. The incision reaction was then reconstituted with the purified proteins RPA, XPA, TFIIH (containing XPB and XPD), XPC, UV-DDB, XPG, partially purified ERCC1/XPF complex, and a factor designated IF7. UV-DDB (related to XPE protein) stimulated repair but was not essential. ERCC1- and XPF-correcting activity copurified with an ERCC1-binding polypeptide of 110 kDa that was absent in XP-F cell extract. Complete repair synthesis was achieved by combining these factors with DNA polymerase epsilon, RFC, PCNA, and DNA ligase I. The reconstituted core reaction requires about 30 polypeptides.
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PMID:Mammalian DNA nucleotide excision repair reconstituted with purified protein components. 769 16

The genetic disorders xeroderma pigmentosum (XP), Cockayne syndrome (CS), and trichothiodystrophy (TTD) are all associated with defects in nucleotide excision repair (NER) of DNA damage. Their clinical features are very different, however, XP being a highly cancer-prone skin disorder, whereas CS and TTD are cancer-free multisystem disorders. All three are genetically complex, with at least eight complementation groups for XP (XP-A to -G and variant), five for CS (CS-A, CS-B, XP-B, XP-D, and XP-G), and three for TTD (XP-B, XP-D, and TTD-A). With the exception of the variant, the products of the XP genes are proteins involved in the different steps of NER, and comprise three damage-recognition proteins, two helicases, and two nucleases. The two helicases, XPB and XPD, are components of the basal transcription factor TFIIH, which has a dual role in NER and initiation of transcription. Different mutations in these genes can affect NER and transcription differentially, and this accounts for the different clinical phenotypes. Mutations resulting in defective repair without affecting transcription result in XP, whereas if transcription is also affected, TTD is the outcome. CS proteins are only involved in transcription-coupled repair, a subpathway of NER in which damage in the transcribed strands of active genes is rapidly and preferentially repaired. Current evidence suggests that they also have an important but not essential role in transcription. The variant form of XP is defective in a novel DNA polymerase, which is able to synthesise DNA past UV-damaged sites.
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PMID:Xeroderma pigmentosum and related disorders: defects in DNA repair and transcription. 1103 99

DNA repair may be a determinant of the susceptibility of the conceptus to DNA damaging teratogens. The nucleotide excision repair (NER) pathway repairs a substantial amount of chemically induced DNA damage. The goals of this study were to assess the coordinate expression of NER genes in the midorganogenesis-stage rat conceptus and determine the consequences of exposure to the genotoxic teratogen, 4-hydroperoxycyclophosphamide (4-OOHCPA), on NER gene expression. Most NER genes were expressed at low levels in both yolk sac and embryo on gestational day (GD) 10, with the exception of XPD, XPE and PCNA. No significant alterations in gene expression occurred between GDs 10 and 11; in the yolk sac XPB expression increased on GD12 compared to either GD10 or 11. In the embryo, XPE expression increased between GDs 10 and 12, while hHR23B, XPB, ERCC1, and DNA polymerase epsilon expression increased on GD12 relative to both GDs 10 and 11. Contrary to gene expression data, XPB protein was found at high levels and XPD at low levels in GDs 10-12 embryos and yolk sacs. Mirroring gene expression, high levels of PCNA protein were found in both tissues; XPA protein levels were minimal in yolk sac from GDs 10-12 but increased in the embryo from moderate on GD10 to high on GD12. Therefore, NER gene expression during organogenesis was regulated in a developmental stage- and tissue-specific manner. Exposure of the conceptus to a teratogen, 4-OOHCPA, induced malformations without affecting NER transcript levels. Thus, NER gene expression in the conceptus was unresponsive to regulation by DNA alkylation.
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PMID:Nucleotide excision repair gene expression in the rat conceptus during organogenesis. 1142 16