Search results for "violet"
showing 10 items of 883 documents
c-Fos is required for excision repair of UV-light induced DNA lesions by triggering the re-synthesis of XPF
2006
Cells deficient in c-Fos are hypersensitive to ultraviolet (UV-C) light. Here we demonstrate that mouse embryonic fibroblasts lacking c-Fos (fos-/-) are defective in the repair of UV-C induced DNA lesions. They show a decreased rate of sealing of repair-mediated DNA strand breaks and are unable to remove cyclobutane pyrimidine dimers from DNA. A search for genes responsible for the DNA repair defect revealed that upon UV-C treatment the level of xpf and xpg mRNA declined but, in contrast to the wild type (wt), did not recover in fos-/- cells. The observed decline in xpf and xpg mRNA is due to impaired re-synthesis, as shown by experiments using actinomycin D. Block of xpf transcription resu…
Fen1 is induced p53 dependently and involved in the recovery from UV-light-induced replication inhibition.
2005
Mouse embryonic fibroblasts (MEFs) that lack p53 are hypersensitive to the cytotoxic and genotoxic effect of ultraviolet (UV-C) light. They also display a defect in the recovery from UV-C-induced DNA replication inhibition. An enzyme involved in processing stalled DNA replication forks is flap endonuclease 1 (Fen1). Gene expression profiling of UV-C-irradiated MEFs revealed fen1 to be upregulated, which was confirmed by RT-PCR and Western blot experiments. Increased Fen1 levels upon UV-C exposure are due to transcriptional activation, as revealed by inhibitor studies. Fen1 induction was dose- and time-dependent; it occurred on protein level already 3 h after irradiation. Induction of Fen1 b…
Ras-Related GTPase RhoB Forces Alkylation-Induced Apoptotic Cell Death
2000
rhoB encoding a Ras-related GTPase is immediate-early inducible by genotoxic treatments. To address the question of the physiological role of RhoB in cellular defense, cells stably overexpressing wild-type RhoB protein were generated. Overexpression of RhoB renders cells hypersensitive to the killing effect of alkylating agents including antineoplastic drugs but not to UV-light and doxorubicin. As compared to control cells, RhoB overexpressing cells revealed an increase in the frequency of alkylation-induced apoptotic cell death. This indicates that RhoB is involved in modulating apoptotic signaling. Furthermore, overexpression of RhoB resulted in a prolonged transient block to DNA replicat…
Effect of Ultraviolet Irradiation on Biosynthesis of Dna in Guinea-Pig Skin in Vivo
1974
The molecular and metabolic alterations preceding the clinical manifestation of a photobiologic process, the erythematous or sunburn reaction, were investigated in mammalian skin in vivo. The effect of a moderate (2.5–3 times the minimal erythema dose [MED]) and a large (6–8 times MED) dose of ultraviolet radiation (290–320 nm) on the incorporation of [ Me - 3 H]-thymidine into epidermal cell DNA of guinea pigs was studied. The epilated half of the back of each animal was irradiated with various doses of ultraviolet light, and the other half served as the nonirradiated control. The amount of intraperitoneally injected [ Me - 3 H]-thymidine incorporated into the DNA was determined by the iso…
How DNA lesions are turned into powerful killing structures: Insights from UV-induced apoptosis
2008
Mammalian cells treated with ultraviolet (UV) light provide one of the best-known experimental systems for depicting the biological consequences of DNA damage. UV irradiation induces the formation of DNA photoproducts, mainly cyclobutane pyrimidine dimers (CPDs) and (6-4) pyrimidine-pyrimidone photoproducts [(6-4)PPs], that drastically impairs DNA metabolism, culminating in the induction of cell death by apoptosis. While CPDs are the most important apoptosis-inducing lesions in DNA repair proficient cells, recent data indicates that (6-4)PPs also signals for apoptosis in DNA repair deficient cells. The toxic effects of these unrepaired DNA lesions are commonly associated with transcription …
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…
Ultraviolet light-induced apoptotic death is impaired by the HMG-CoA reductase inhibitor lovastatin.
2003
HMG-CoA reductase inhibitors (i.e., statins) attenuate C-terminal isoprenylation of Rho GTPases, thereby inhibiting UV-C-induced activation of c-Jun-N-terminal kinases/stress-activated protein kinases (JNKs/SAPKs). Inhibition of UV-C-triggered JNK/SAPK activation by lovastatin is due to inhibition of Rac-SEK1/MKK4-mediated phosphorylation of JNKs/SAPKs at Thr183/Tyr185. UV-C-stimulated phosphorylation of p38 kinase (Thr180/Tyr182) is also impaired by lovastatin. Cell killing provoked by UV-C irradiation was significantly inhibited by lovastatin. This was paralleled by a reduced frequency of chromosomal aberrations, accelerated recovery from UV-C-induced transient replication blockage, inhib…
Experimental and theoretical studies on thymine photodimerization mediated by oxidatively generated DNA lesions and epigenetic intermediates.
2020
[EN] Interaction of nucleic acids with light is a scientific question of paramount relevance not only in the understanding of life functioning and evolution, but also in the insurgence of diseases such as malignant skin cancer and in the development of biomarkers and novel light-assisted therapeutic tools. This work shows that the UVA portion of sunlight, not absorbed by canonical DNA nucleobases, can be absorbed by 5-formyluracil (ForU) and 5-formylcytosine (ForC), two ubiquitous oxidatively generated lesions and epigenetic intermediates present in living beings in natural conditions. We measure the strong propensity of these molecules to populate triplet excited states able to transfer th…
Photoinduced DNA damage efficiency and cytotoxicity of novel viologen linked pyrene conjugates.
2010
Novel viologen linked pyrene conjugates permeate cells efficiently and exhibit spacer length dependent DNA damage and cytotoxicity upon photoexcitation.
Characterization of Different Deoxyribonucleases in Human Lymphocytes
1975
Abstract Deoxyribonucleases, Disc Electrophoresis, Lymphocytes Four groups of deoxyribonuclease activities from human lymphocytes have been characterized by deoxyribonuclease assay in DNA-containing polyacrylamide gels following their separation by disc-electrophoresis. All activities hydrolyse DNA endonucleolytically. One neutral deoxyribo nuclease found in the cytoplasmic fraction prefers native or UV-irradiated DNA over denatured DNA as substrate and is a 5′-monoester former. Two groups of acid deoxyribonuclease activities are detectable in the nuclear fraction. Both are 3′-monoester formers. One is as well active with denatured DNA as with native DNA, the other one shows the same activ…