Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.5.1.2 (DNA ligase)
 2,749 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

DNA polymerase beta (pol beta) is a constitutively expressed DNA repair enzyme in vertebrate cells. Yet, it had been shown previously that the pol beta mRNA level increases in Chinese hamster ovary (CHO) cells within 4 h after treatment with several monofunctional DNA damaging agents, notably, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Herein we report that a transfected pol beta promoter fusion gene is activated by MNNG treatment of CHO cells; mRNA from the transfected gene is approximately 10-fold higher in treated cells than in untreated cells 16 h after treatment. This activation is mediated through the decanucleotide palindromic element GTGACGTCAC at positions -49 to -40 in the "TATA-less" core promoter. This element, which is similar to the ATF/CREB transcription factor-binding site in a number of mammalian genes, forms the center of a strong protein-binding site for CHO cell nuclear extract proteins. Mutated pol beta promoter fusion genes lacking the element fail to bind protein at this site and fail to respond to MNNG treatment of cells.
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PMID:The ATF/CREB transcription factor-binding site in the polymerase beta promoter mediates the positive effect of N-methyl-N'-nitro-N-nitrosoguanidine on transcription. 182 4

The mammalian DNA repair enzyme beta-polymerase is encoded by a single-copy gene that is expressed in all tissues and cell lines studied to date. A protein fraction with high binding affinity for an ATF/CREB-like binding element, GTGACGTCAC, at -49 to -40 in the core beta-polymerase promoter has been purified to near-homogeneity from a nuclear extract of bovine testes. The major binding activity, as monitored by gel mobility shift assay, is recovered in 20% yield by a procedure involving oligonucleotide affinity chromatography. The purified protein yields DNase I footprinting and gel shift binding patterns indistinguishable from the activity in crude extracts. The final fraction activates transcription in an in vitro transcription reaction. The native molecular weight of the purified binding activity is about 100-120K as measured by gel filtration. SDS-PAGE of the purified fraction revealed that it contains several polypeptides in the molecular weight range of 30-52K, yet two of these peptides (Mr 49K and 52K) are predominant. Specific binding to the palindrome is salt-sensitive and is consistent with the formation of nine ion pairs (from log KA vs log KCl plots) and has a KA at 200 mM KCl of 5.8 X 10(11) M-1. Kinetic studies with synthetic oligonucleotides as binding ligands indicate that the purified protein can bind tighter to or discriminate between the beta-polymerase ATF/CREB element and similar elements derived from somatostatin and chorionic gonadotropin genes.
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PMID:Mammalian beta-polymerase promoter: large-scale purification and properties of ATF/CREB palindrome binding protein from bovine testes. 182 81

The multifunctional mammalian apurinic/apyrimidinic (AP) endonuclease (APE) is responsible for the repair of AP sites in DNA. In addition, this enzyme has been shown to function as a redox factor facilitating the DNA-binding capability of JUN and FOS, HeLa AP-1, and numerous other transcription factors, including Myb, members of the CREB family and nuclear factor-kappa B. Although previously presumed to be ubiquitously expressed at comparable levels in all tissues and cell types, recent evidence has shown APE to vary significantly in its expression between tissues and even within tissues. To further characterize APE expression at various stages of cervical neoplasia, we investigated the levels of APE protein expression using immunohistochemistry in normal cervix, pre-invasive and invasive squamous lesions of the cervix, as well as in cervical cancer cell lines. We report here that the APE protein is predominantly expressed in the nuclei of cells from both primary tumors and cervical cell lines, but the level of APE protein is significantly and dramatically elevated in cervical cancer tissue. These results implicate the use of anti-APE antibodies as an effective reagent in the early detection of premalignant and malignant cancer of the cervix. These findings are suggestive that the increase of a DNA repair enzyme in cancerous cells may allow these cells to be refractive to chemotherapy.
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PMID:The apurinic/apyrimidinic endonuclease (APE/ref-1) DNA repair enzyme is elevated in premalignant and malignant cervical cancer. 942 67

The DNA alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) upregulates the level of the base excision DNA repair enzyme DNA polymerase beta (beta-pol) in several mammalian cell types. Previous studies suggested that beta-pol expression is upregulated via a transcriptional mechanism that requires: the specific cAMP response element (CRE) in the beta-pol core promoter; a phosphorylated form of CRE-binding protein-1 (CREB-1); and cellular protein kinase A activity. A large family of CRE-binding proteins, ie., the ATF/CREB factors, has been identified in various cell types. This study further examines the role of CRE-binding proteins in regulating beta-pol expression through study of Chinese hamster ovary (CHO) cells. In CHO cell nuclear extract, CREB-1 and ATF-1 are the predominant CRE-binding protein family members recognizing the CRE in the beta-pol core promoter. The concentration of CREB-1 increases strongly in CHO cells after exposure to MNNG. In contrast, the level of ATF-1 does not change after MNNG treatment. Recombinant expression of CREB-1 in CHO cells is sufficient to increase expression of the endogenous beta-pol gene, even in the absence of MNNG exposure. These results indicate that beta-pol gene expression in CHO cells can be upregulated by CREB-1 and that the activation of beta-pol gene expression in response to DNA alkylating agent exposure involves a strong increase in the level of CREB-1.
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PMID:DNA polymerase beta gene expression: the promoter activator CREB-1 is upregulated in Chinese hamster ovary cells by DNA alkylating agent-induced stress. 1267 96

The co-transcription factor and DNA repair enzyme, Redox effector factor-1/apurinic/apyrimidinic endonuclease (Ref-1/Ape), facilitates DNA binding and transcriptional activity of a number of transactivating factors, including those governing hypoxia-induced gene expression HIF-1. It is not known, however, whether Ref-1/Ape is a component of the hypoxic transcriptional complex. Electrophoretic mobility shift assays failed to detect direct DNA binding of Ref-1/Ape to either the HIF-1 or AP1 DNA recognition sequences present in the hypoxic response element of the VEGF gene. However, immunodepletion of Ref-1/Ape from nuclear extract prevented DNA binding of ATF/CREB and HIF-1 to the HIF-1 DNA recognition sequence. DNA affinity-precipitation analyses showed that Ref-1/Ape was part of the multiprotein transcriptional complex forming on a 64-mer sequence encompassing a minimal hypoxic response element. Immunodepletion of Ref-1/Ape prevented probe association with HIF-1, p300, ATF, and CREB. Co-immunoprecipitation experiments indicated that Ref-1/Ape present in nuclear extract interacted with HIF-1 and p300 but not ATF/CREB. However, when Ref-1/Ape was immunoprecipitated from the oligonucleotide probe, both HIF-1 and p300 remained probe-associated while ATF/CREB co-immunoprecipitated. These findings suggest that Ref-1/Ape is a critical component of the hypoxia-inducible transcriptional complex forming on the VEGF gene's hypoxic response element and that the presence of Ref-1/Ape in the complex is required for the apparent high affinity association between HIF-1 and its DNA recognition sequence.
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PMID:Ref-1/Ape is critical for formation of the hypoxia-inducible transcriptional complex on the hypoxic response element of the rat pulmonary artery endothelial cell VEGF gene. 1508 19

Arsenite is a human carcinogen causing skin, bladder, and lung tumors, but the cellular mechanisms underlying these effects remain unclear. We investigated expression of the essential base excision DNA repair enzyme apurinic endonuclease 1 (Ape1) in response to sodium arsenite. In mouse 10T(1/2) fibroblasts, Ape1 induction in response to arsenite occurred about equally at the mRNA, protein, and enzyme activity levels. Analysis of the APE1 promoter region revealed an AP-1/CREB binding site essential for arsenite-induced transcriptional activation in both mouse and human cells. Electrophoretic mobility shift assays indicated that an ATF4/c-Jun heterodimer was the responsible transcription factor. RNA interference targeting c-Jun or ATF4 eliminated arsenite-induced APE1 transcription. Suppression of Ape1 or ATF4 sensitized both mouse fibroblasts (10T(1/2)) and human lymphoblastoid cells (TK6) to arsenite cytotoxicity. Expression of Ape1 from a transgene did not efficiently restore arsenite resistance in ATF4-depleted cells but did offset initial accumulation of abasic DNA damage following arsenite treatment. Mutagenesis by arsenite (at the TK and HPRT loci in TK6 cells) was observed only for ATF4-depleted cells, which was strongly offset by Ape1 expression from a transgene. Therefore, the ATF4-mediated up-regulation of Ape1 and other genes plays a key role against arsenite-mediated toxicity and mutagenesis.
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PMID:ATF4-dependent oxidative induction of the DNA repair enzyme Ape1 counteracts arsenite cytotoxicity and suppresses arsenite-mediated mutagenesis. 1793 2