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)

Studies on human patients and experimental animals indicate that hyperbaric O2 can opacify the lens nucleus and damage the lens epithelium in vivo. Here we investigate the effects of hyperbaric O2 on cultured rabbit lens epithelial cells (LECs). When the cells were exposed to 50 atm O2 (99% O2 + 1% CO2) for 3 hr there were no immediate effects on morphology, viability and transport processes (uptake of 86Rb and 14C-alpha AIB). In addition, the O2 treatment did not lower the high level of reduced glutathione or increase the low level of oxidized glutathione. However, 50 atm O2 did produce a near doubling in the glycolytic rate which maintained ATP at levels only slightly lower than normal. Although the 3-hr O2 treatment was not lethal, it completely inhibited cell division for 2 days. After 2 days, growth was initiated and, at day 7 the rate of growth was faster than the controls (control cells were treated with ambient air or 50 atm N2 for 3 hr). Cells treated with 8 atm O2 for 3 hr exhibited a slowed rate of growth, relative to controls, while exposure to 2 atm O2, did not inhibit mitosis. Changes in morphology (multilayering and elongation) of cells exposed to 50 atm O2, but not the controls, were evident 7 days after the 3-hr exposure. The incorporation of [35S]methionine into individual polypeptides and [3H]thymidine into DNA was significantly inhibited immediately following a 3-hr treatment with 50 atm O2, but both parameters recovered within 2 days. DNA strand breaks were observed in LECs following hyperbaric O2 treatment as low as 4 atm O2 for 3 hr and increased with higher pressures of O2, but not N2. Treatment with 50 atm O2 nearly doubled the activity of the DNA repair enzyme, poly-ADP-ribose polymerase, and decreased the level of its substrate NAD+; the latter effect was reduced by 3-aminobenzamide, an inhibitor of the enzyme. Thus, although LECs tolerated brief exposures to high pressures of O2 without cell death, DNA damage occurred at relatively low pressures of O2. All of the effects of hyperbaric O2 on LECs occurred without any alteration of the normal levels of reduced and oxidized glutathione. It appears that GSH is important in maintaining cell viability during exposure to an elevated level of O2, but that it is incapable of preventing O2-induced effects on growth and DNA.
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PMID:Hyperbaric oxygen inhibits the growth of cultured rabbit lens epithelial cells without affecting glutathione level. 850 May 57

DNA-damaging agents usually produce a vast collection of lesions within the genome. Analysis of these lesions from the structural and biological viewpoints is often complicated by the reality that some of the lesions are chemically fragile, leading to an even larger set of secondary and tertiary products. In an effort to deconvolute complex DNA-damage spectra, a strategy is presented whereby an oligonucleotide containing a specific target for chemical reaction is allowed to react with a DNA-damaging agent. A large collection of HPLC-resolvable modified oligonucleotides is generated, and chromatographically distinct members of the set are then individually characterized using chemical, spectroscopic, biochemical, and genetic probes. The biological component of this "chemical-biological fingerprinting" tool is the use of polymerase bypass in vivo in cells having defined replication status and quantitative and qualitative patterns of lesion-directed mutagenesis, as key properties that complement physical analysis of modified DNA. This approach was applied to the complex product spectrum generated by peroxynitrite in the presence of CO2; peroxynitrite is a powerful oxidizing and nitrating agent generated as part of immune response. An oligonucleotide containing the primary oxidation product, 7,8-dihydro-8-oxoguanine (8-oxoGua), which is highly susceptible to further oxidation and/or nitration, was treated with peroxynitrite. Using mass spectrometry, coelution with authentic standards, sensitivity to piperidine, recognition and strand cleavage by the DNA repair enzyme MutM, and mutagenicity and genotoxicity in vivo, a matrix was created that defined the properties of the secondary DNA lesions formed when 3-morpholinosydnonimine (SIN-1) delivered a low, constant flux of peroxynitrite to an oligonucleotide containing 8-oxoGua. Two lesions were identified as the diastereomers of spiroiminodihydantoin (Sp), which had been observed previously in nucleoside-based experiments employing SIN-1. A third lesion, triazine, was tentatively identified. However, in addition to these lesions, a number of secondary lesions were generated that had chemical-biological fingerprints inconsistent with that of any known 8-oxoGua-derived lesion described to date. In vitro experiments showed that while some of these newly characterized secondary lesions were removed from DNA by MutM, others were in fact very poor substrates for this repair enzyme. These 8-oxoGua-derived lesions also showed varying degrees of sensitivity to piperidine. Furthermore, all of the secondary lesions observed in this work were potently mutagenic and genotoxic in Escherichia coli. Therefore, while 8-oxoGua itself is nontoxic and only mildly mutagenic in repair-proficient cells, peroxynitrite reveals the promutagenic potential and triggers the covert nature of this DNA lesion.
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PMID:Chemical-biological fingerprinting: probing the properties of DNA lesions formed by peroxynitrite. 1794 98