Long-Range Enhancer Associated with Chromatin Looping Allows AP-1 Regulation of the Peptidylarginine Deiminase 3 Gene in Differentiated Keratinocyte

Transcription control at a distance is a critical mechanism, particularly for contiguous genes. The peptidylarginine deiminases (PADs) catalyse the conversion of protein-bound arginine into citrulline (deimination), a critical reaction in the pathophysiology of multiple sclerosis, Alzheimer's disease and rheumatoid arthritis, and in the metabolism of the major epidermal barrier protein filaggrin, a strong predisposing factor for atopic dermatitis. PADs are encoded by 5 clustered PADI genes (1p35-6). Unclear are the mechanisms controlling the expression of the gene PADI3 encoding the PAD3 isoform, a strong candidate for the deimination of filaggrin in the terminally differentiating epidermal keratinocyte. We describe the first PAD Intergenic Enhancer (PIE), an evolutionary conserved non coding segment located 86-kb from the PADI3 promoter. PIE is a strong enhancer of the PADI3 promoter in Ca2+-differentiated epidermal keratinocytes, and requires bound AP-1 factors, namely c-Jun and c-Fos. As compared to proliferative keratinocytes, calcium stimulation specifically associates with increased local DNase I hypersensitivity around PIE, and increased physical proximity of PIE and PADI3 as assessed by Chromosome Conformation Capture. The specific AP-1 inhibitor nordihydroguaiaretic acid suppresses the calcium-induced increase of PADI3 mRNA levels in keratinocytes. Our findings pave the way to the exploration of deimination control during tumorigenesis and wound healing, two conditions for which AP-1 factors are critical, and disclose that long-range transcription control has a role in the regulation of the gene PADI3. Since invalidation of distant regulators causes a variety of human diseases, PIE results to be a plausible candidate in association studies on deimination-related disorders or atopic disease

Larger yield of cyclobutane dimers than 8-oxo-7,8-dihydroguanine in the DNA of UVA-irradiated human skin cells

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Cyclobutane pyrimidine dimers are predominant DNA lesions in whole human skin exposed to UVA radiation

International audienceSolar UV radiation is the most important environmental factor involved in the pathogenesis of skin cancers. The well known genotoxic properties of UVB radiation (290-320 nm) mostly involve bipyrimidine DNA photoproducts. In contrast, the contribution of more-abundant UVA radiation (320-400 nm) that are not directly absorbed by DNA remains poorly understood in skin. Using a highly accurate and quantitative assay based on HPLC coupled with tandem mass spectrometry, we determined the type and the yield of formation of DNA damage in whole human skin exposed to UVB or UVA. Cyclobutane pyrimidine dimers, a typical UVB-induced DNA damage, were found to be produced in significant yield also in whole human skin exposed to UVA through a mechanism different from that triggered by UVB. Moreover, the latter class of photoproducts is produced in a larger amount than 8-oxo-7,8-dihydro-2-deoxyguanosine, the most common oxidatively generated lesion, in human skin. Strikingly, the rate of removal of UVA-generated cyclobutane pyrimidine dimers was lower than those produced by UVB irradiation of skin. Finally, we compared the formation yields of DNA damage in whole skin with those determined in primary cultures of keratinocytes isolated from the same donors. We thus showed that human skin efficiently protects against UVB-induced DNA lesions, whereas very weak protection is afforded against UVA. These observations emphasize the likely role played by the UVA-induced DNA damage in skin carcinogen-esis and should have consequences for photoprotection strategies

Electron spin resonance detection of oxygen radicals released by UVA-irradiated human fibroblasts

This work reports the electron spin resonance (ESR) detection of oxygenated radicals (OR) released by cultured human fibroblasts after UVA (365 nm) exposure. 5,5-dimethyl-pyrroline-N-oxide (DMPO) was used as spin trap. After a UVA irradiation of one hour, followed by a latent period of at least 45 min., and an incubation time of 30 min. in a trapping medium containing DMPO, glucose, Na+, K+ and Ca2+ an ESR signal was recorded. By contrast, an ESR signal was produced after only 15 min. incubation when calcium ionophore A23187 was used. Although the ESR signal was characteristic of the hydroxyl adduct DMPO-OH, the use of catalase and superoxide dismutase (SOD) revealed that UVA stimulated fibroblasts released the superoxide anion O$_2^-$ in the medium. SOD, vitamin C and (+)-catechin inhibited the release of superoxide generated by human fibroblasts stimulated with A23187 calcium ionophore at 5 units/ml, 10-5 M and $2\times 10^{-4}$ M, respectively

Interexperimental and interindividual variations of DNA repair capacities after UV-13 and UV-C irradiations of human keratinocytes and fibroblasts

International audienceComment être féministe et militante de gauche ? Cette question se pose avec toute sa gravité lors des débats autour du suffrage féminin, le 30 septembre et le 1 er octobre 1931. Venant juste d'être élue députée socialiste pour Badajoz, Margarita Nelken 1 n'a pas pu participer aux discussions, mais elle a exprimé par écrit son opposition à la concession du droit de vote aux femmes dans La mujer ante las Cortes Constituyentes. Ce refus est considéré comme étant la première d'une suite de « trahisons » de Nelken 2 , une double trahison en tant que féministe de longue date et en tant que socialiste. En effet, lors du congrès du PSOE en 1931, organisé pour fixer la ligne des socialistes dans le processus d'élaboration de la nouvelle constitution, le droit de vote des femmes avait été adopté malgré les réticences de certaines fédérations ou de certains courants (NELKEN, 1931 : 15-16) 3. On comprend alors que Margarita Nelken apparaisse comme étant l'une des figures féminines les plus controversées. Selon Antonina Rodrigo, les témoignages impartiaux à son égard-mémoires ou récits autobiographiques de dirigeants politiques-sont rares et il est difficile de trouver des jugements favorables à son action et à son talent intellectuel (RODRIGO, 1996 : 279). Mais la controverse ne se limite pas aux protagonistes de cette période de l'histoire de l'Espagne. On ne peut que constater un certain silence historiographique puisque les études sur Margarita Nelken sont peu nombreuses et concentrées sur son opposition au suffrage féminin ou sur son action pendant la guerre civile. Comme l'autre députée femme qui s'opposa au droit de vote des femmes, Victoria Kent, Nelken souffre d'un oubli qui seulement de nos jours commence à être brisé. Margarita Nelken constitue à nos yeux un bon exemple de la complexité de la question du rapport des femmes à l'Histoire. D'une part, c'est une femme célèbre, qui a dû se battre dans un univers masculin pour exister en tant qu'intellectuelle et que militante et dont la vie a été écrite par les hommes ou en fonction d'une logique masculine. D'autre part, c'est une femme qui fait sa propre histoire et, surtout, qui l'écrit puisque-et c'est la base de notre réflexion-chaque tournant de sa vie et chaque prise de position importante sont fixés par une oeuvre écrite. Ce travail s'organisera autour des deux questions qui structurent le parcours vital de Margarita Nelken : comment être féministe et comment être une femme politiquement engagée