Search results for "OxyR"
showing 10 items of 216 documents
A Thermophilic Tetramolecular G-Quadruplex/Hemin DNAzyme.
2017
International audience; The quadruplex-based DNAzyme system is one of the most useful artificial enzymes or catalysts; their unique properties make them reliable alternatives to proteins for performing catalytic transformation. The first prototype of a thermally stable DNAzyme system is presented. This thermophilic DNAzyme is capable of oxidizing substrates at high temperatures (up to 95 degrees C) and long reaction times (up to 18 h at 75 degrees C). The catalytic activity of the DNAzymes were investigated with the standard peroxidase-mimicking oxidation of 2,2'-azino-bis(3-ethylbenzothiozoline-6-sulfonic acid) (ABTS) by H2O2. The step-by-step design of this unique heat-activated G-quadrup…
Nuclear receptors modulate the interaction of Sp1 and GC-rich DNA via ternary complex formation
2000
Binding sites for transcription factor Sp1have been implicated in the transcriptional regulation of several genes by hormones or vitamins, and here we show that a GC-rich element contributes to the retinoic acid response of the interleukin 1β promoter. To explain such observations, it has been proposed that nuclear receptors can interact with Sp1 bound to GC-rich DNA. However, evidence supporting this model has remained indirect. So far, nuclear receptors have not been detected in a complex with Sp1 and GC-rich DNA, and the expected ternary complexes in non-denaturing gels were not seen. In search for these missing links we found that nuclear receptors [retinoic acid receptor (RAR), thyroid…
Alternative splicing products of the tenascin gene distinguish rat liver fat storing cells from arterial smooth muscle cells and skin fibroblasts
1992
Abstract Fat storing-(Ito-)cells (FSC) transform into a myofibroblast-like cell type during liver fibrogenesis. A similar development can be observed in cell culture. At the moment, a definite marker to differentiate transformed FSC from smooth muscle cells (SMC) is not available. We recently found that FSC, SMC and skin fibroblasts (SF) synthesize tenascin, a novel matrix protein. As it is reported that various tissues express different tenascin forms by the mechanism of alternative pre-mRNA splicing, we analyzed the tenascin transcripts in these cell types. Total RNA extracted from cultured FSC, SMC and SF, analyzed by Northern blot hybridization, showed a 7.2 kb transcript in FSC, a 8.7 …
Benzo[a]pyrene represses DNA repair through altered E2F1/E2F4 function marking an early event in DNA damage-induced cellular senescence
2020
AbstractTranscriptional regulation of DNA repair is of outmost importance for the restoration of DNA integrity upon genotoxic stress. Here we report that the potent environmental carcinogen benzo[a]pyrene (B[a]P) activates a cellular DNA damage response resulting in transcriptional repression of mismatch repair (MMR) genes (MSH2, MSH6, EXO1) and of RAD51, the central homologous recombination repair (HR) component, ultimately leading to downregulation of MMR and HR. B[a]P-induced gene repression is caused by abrogated E2F1 signalling. This occurs through proteasomal degradation of E2F1 in G2-arrested cells and downregulation of E2F1 mRNA expression in G1-arrested cells. Repression of E2F1-me…
Regulation of ribonucleotide reductase in response to iron deficiency
2011
Ribonucleotide reductase (RNR) is an essential enzyme required for DNA synthesis and repair. Although iron is necessary for class Ia RNR activity, little is known about the mechanisms that control RNR in response to iron deficiency. In this work, we demonstrate that yeast cells control RNR function during iron deficiency by redistributing the Rnr2–Rnr4 small subunit from the nucleus to the cytoplasm. Our data support a Mec1/Rad53-independent mechanism in which the iron-regulated Cth1/Cth2 mRNA-binding proteins specifically interact with the WTM1 mRNA in response to iron scarcity, and promote its degradation. The resulting decrease in the nuclear-anchoring Wtm1 protein levels leads to the re…
Heat shock protein-antigen fusions lose their enhanced immunostimulatory capacity after endotoxin depletion.
2008
Heat shock proteins (HSPs) induce cross-presentation of antigens by dendritic cells (DC) as well as DC maturation. These properties make HSP antigen complexes good candidates to prime CD8 T cell responses against tumor-associated antigens. In this study, we analyzed four different members of the HSP70 family fused to a fragment of ovalbumin (OVA) as a model tumor antigen. E. coli-derived recombinant HSP70-OVA fusion proteins efficiently primed antigen-specific cytotoxic T cells in short-term in vivo immunization assays. Because of concerns that the adjuvant effect of HSPs may be due to endotoxin contamination, we studied this issue in detail. Induction of OVA-specific cytotoxicity was signi…
DNA oxidation products determined with repair endonucleases in mammalian cells: Types, basal levels and influence of cell proliferation
1999
Purified repair endonucleases such as Fpg protein, endonuclease III and IV allow a very sensitive quantification of various types of oxidative DNA modifications in mammalian cells. By means of these assays, the numbers of base modifications sensitive to Fpg protein, which include 8-hydroxyguanine (8-oxoG), were determined to be less than 0.3 per 10(6) bp in several types of untreated cultured mammalian cells and human lymphocytes and less than 10 per 10(6) bp in mitochondrial DNA from rat and porcine liver. Oxidative 5,6-dihydropyrimidine derivatives sensitive to endonuclease III and sites of base loss sensitive to endonuclease IV or exonuclease III were much less frequent than Fpg-sensitiv…
Molecular and functional analysis of the (6-4) photolyase from the hexactinellid Aphrocallistes vastus.
2003
The hexactinellid sponges (phylum Porifera) represent the phylogenetically oldest metazoans that evolved 570-750 million years ago. At this period exposure to ultraviolet (UV) light exceeded that of today and it may be assumed that this old taxon has developed a specific protection system against UV-caused DNA damage. A cDNA was isolated from the hexactinellid Aphrocallistes vastus which comprises high sequence similarity to genes encoding the protostomian and deuterostomian (6-4) photolyases. Subsequently functional studies were performed. It could be shown that the sponge gene, after transfection into mutated Escherichia coli, causes resistance of the bacteria against UV light. Recombinan…
Influences of histone deacetylase inhibitors and resveratrol on DNA repair and chromatin compaction
2013
Accessibility of DNA is a prerequisite for both DNA damage and repair. Therefore, the chromatin structure is expected to have major impact on both processes, with opposite consequences for the stability of the genome. To analyse the influence of chromatin compaction on the generation and repair of various types of DNA modifications, we modulated the global chromatin structure of AS52 Chinese hamster ovary cells and HeLa cells by treatment with either histone deacetylase inhibitors or resveratrol and measured the repair kinetics of (i) pyrimidine dimers induced by ultraviolet B, (ii) oxidised purines generated by photosensitisation and (iii) single-strand breaks induced by H2O2, using an alk…
Influence of dibutyryl cyclic AMP on thymidine uptake by herpes simplex virus infected cells and the intracellular level of cyclic AMP.
1977
Abstract Dibutyryl cyclic AMP inhibits the increase of dThd and BrdUrd transport normally observed after infection with Herpesvirus hominis, type I and II. Incorporation is also reduced. Inhibition of uptake is non-competitive as analysed by the Lineweaver-Burk plot. Addition of this drug to infected cells also reduces the activity of the thymidine kinase (EC 2.7.1.75). Transport of dUrd, dCyd and dAdo is not reduced. 4–8 h after infection with thymidine kinase (+) herpes strains the level of cAMP increases. On infection with a thymidine kinase (−) virus, only a small elevation of cAMP can be shown. It was also found that early addition of actinomycin D or of cycloheximide prevents the incr…