Ultraviolet light

About: Ultraviolet light is a research topic. Over the lifetime, 49494 publications have been published within this topic receiving 843151 citations.

Signals from within: the DNA-damage-induced NF-κB response

Abstract: An appropriate response to genotoxic stress is essential for maintenance of genome stability and avoiding the passage to neoplasia. Nuclear factor κB (NF-κB) is activated as part of the DNA damage response and is thought to orchestrate a cell survival pathway, which, together with the activation of cell cycle checkpoints and DNA repair, allows the cell in cases of limited damage to restore a normal life cycle, unharmed. In this respect, NF-κB is one of the main factors accounting for chemotherapy resistance and as such impedes effective cancer treatment, representing an important drug target. Despite this high clinical relevance, signalling cascades leading to DNA damage-induced NF-κB activation are poorly understood and the use of highly divergent experimental set-ups in the past led to many controversies in the field. Therefore, in this review, we will try to summarize the current knowledge of distinct DNA damage-induced NF-κB signalling pathways.

Light Controls Growth and Development via a Conserved Pathway in the Fungal Kingdom

Abstract: Light inhibits mating and haploid fruiting of the human fungal pathogen Cryptococcus neoformans, but the mechanisms involved were unknown. Two genes controlling light responses were discovered through candidate gene and insertional mutagenesis approaches. Deletion of candidate genes encoding a predicted opsin or phytochrome had no effect on mating, while strains mutated in the white collar 1 homolog gene BWC1 mated equally well in the light or the dark. The predicted Bwc1 protein shares identity with Neurospora crassa WC-1, but lacks the zinc finger DNA binding domain. BWC1 regulates cell fusion and repression of hyphal development after fusion in response to blue light. In addition, bwc1 mutant strains are hypersensitive to ultraviolet light. To identify other components required for responses to light, a novel self-fertile haploid strain was created and subjected to Agrobacterium-mediated insertional mutagenesis. One UV-sensitive mutant that filaments equally well in the light and the dark was identified and found to have an insertion in the BWC2 gene, whose product is structurally similar to N. crassa WC-2. The C. neoformans Bwc1 and Bwc2 proteins interact in the yeast two-hybrid assay. Deletion of BWC1 or BWC2 reduces the virulence of C. neoformans in a murine model of infection; the Bwc1-Bwc2 system thus represents a novel protein complex that influences both development and virulence in a pathogenic fungus. These results demonstrate that a role for blue/UV light in controlling development is an ancient process that predates the divergence of the fungi into the ascomycete and basidiomycete phyla.

Characterization of a new photoaffinity derivative of ouabain: labeling of the large polypeptide and of a proteolipid component of the Na, K-ATPase.

Abstract: We have synthesized 2-nitro-5-azidobenzoyl (NAB) derivatives of ouabain as photoaffinity labels of the cardiac glyocoside binding site of Na, K-ATPase. [3HzNAB-ouabain was found to bind to the same number of sites on Na, K-ATPase (purified from pig kidney outer medulla) as ouabain (1.9 nmol/mg), with approximately the same affinity (Kk(ouabain)/Kd(NAB-ouabain) congruent to 1.6), and ouabain was fully competitive uith NAB-ouabain at these sites. NAB-ouabain binding and inhibition were reversible in the dark, but on exposure to ultraviolet light (310-370 nm) 30-40% of the binding and ihibition became irreversible; this binding was shown to be covalent by stability to trichloroacetic acid, organic solvents, and heat denaturation. Covalent labeling was prevented by photolysis of NAB-ouabain prior to the experiment, or by prior incubation of the enzyme with ouabain. On sodium dodecyl suffate-polyacrylamide gels of labeled Na,K-ATPase, about half of the covalently bound [3H]NAB-ouabain migrated with the large polypeptide (molecular weight congruent to 95 000), and half migrated with a small polypeptide (molecular weight congruent to 12 000); noncovalently bound NAB-ouabain (60-70% of total label) ran with the tracking dye. A similar labeling pattern was obtained utilizing NaI microsomes prepared from pig kidney outer medulla. The small polypeptide was characterized as an acidic proteolipid by extractability into acid chloroform/methanol; labeling of this component by NAB-ouabain is the first demonstration that it is directly associated with the Na,K-ATPase. The results of our characterization of NAB-ouabain show that it has the required specificity, covalency, and efficiency of labeling for application in structural studies of Na,K-ATPase subunit interactions.

The radiation response of human malignant melanoma cells grown in vitro.

Abstract: Summary The three malignant melanoma cell lines used are characterized by having high, intermediate , and low quantities of pigment production. The response of these malignant melanoma cells to X-ray in vitro does not correlate with a model of the classically radioresistant tumor cell that clinical experience might predict. The in vitro melanoma cells were only slightly more resistant to X-rays than the nontumor in vitro Chinese hamster ovary cell line tested. The responses to X-rays of all three melanoma lines were the same ( n = 40, D 0 = 100 rads). The response to ultraviolet light varied with the amount of pigment present in each cell line. The strain producing a high quantity of pigment was the most UV resistant ( n = 3, D 0 = 57 ergs/sq mm). The strain producing a low pigment quantity was the most UV sensitive ( n = 3, D 0 = 31 ergs/sq mm). All melanoma strains were more resistant to UV than the Chinese hamster ovary cell line ( n = 10, D 0 = 20 ergs/sq mm). Survival determinations made as a function of time between two fractionated UV doses of 100 + 100 ergs/sq mm indicated that these melanoma cells possessed ability to recover from sublethal UV damage.