DNA compaction by the higher-order assembly of PRH/Hex homeodomain protein oligomers

Protein self-organization is essential for the establishment and maintenance of nuclear architecture and for the regulation of gene expression. We have shown previously that the Proline-Rich Homeodomain protein (PRH/Hex) self-assembles to form oligomeric complexes that bind to arrays of PRH binding sites with high affinity and specificity. We have also shown that many PRH target genes contain suitably spaced arrays of PRH sites that allow this protein to bind and regulate transcription. Here, we use analytical ultracentrifugation and electron microscopy to further characterize PRH oligomers. We use the same techniques to show that PRH oligomers bound to long DNA fragments self-associate to form highly ordered assemblies. Electron microscopy and linear dichroism reveal that PRH oligomers can form protein–DNA fibres and that PRH is able to compact DNA in the absence of other proteins. Finally, we show that DNA compaction is not sufficient for the repression of PRH target genes in cells. We conclude that DNA compaction is a consequence of the binding of large PRH oligomers to arrays of binding sites and that PRH is functionally and structurally related to the Lrp/AsnC family of proteins from bacteria and archaea, a group of proteins formerly thought to be without eukaryotic equivalents

DNA compaction by the higher-order assembly of PRH/Hex homeodomain protein oligomers

Protein self-organization is essential for the establishment and maintenance of nuclear architecture and for the regulation of gene expression. We have shown previously that the Proline-Rich Homeodomain protein (PRH/Hex) self-assembles to form oligomeric complexes that bind to arrays of PRH binding sites with high affinity and specificity. We have also shown that many PRH target genes contain suitably spaced arrays of PRH sites that allow this protein to bind and regulate transcription. Here, we use analytical ultracentrifugation and electron microscopy to further characterize PRH oligomers. We use the same techniques to show that PRH oligomers bound to long DNA fragments self-associate to form highly ordered assemblies. Electron microscopy and linear dichroism reveal that PRH oligomers can form protein–DNA fibres and that PRH is able to compact DNA in the absence of other proteins. Finally, we show that DNA compaction is not sufficient for the repression of PRH target genes in cells. We conclude that DNA compaction is a consequence of the binding of large PRH oligomers to arrays of binding sites and that PRH is functionally and structurally related to the Lrp/AsnC family of proteins from bacteria and archaea, a group of proteins formerly thought to be without eukaryotic equivalents

Characterization of volatile compounds of Daucus crinitus Desf. Headspace Solid Phase Microextraction as alternative technique to Hydrodistillation

<p>Abstract</p> <p>Background</p> <p>Traditionally, the essential oil of aromatic herbs is obtained using hydrodistillation (HD). Because the emitted volatile fraction plays a fundamental role in a plant's life, various novel techniques have been developed for its extraction from plants. Among these, headspace solid phase microextraction (HS-SPME) can be used to obtain a rapid fingerprint of a plant's headspace. <it>Daucus crinitus </it>Desf. is a wild plant that grows along the west coast of Algeria. Only a single study has dealt with the chemical composition of the aerial part oils of Algerian <it>D. crinitus</it>, in which isochavicol isobutyrate (39.0%), octyl acetate (12.3%), and β-caryophyllene (5.4%) were identified. Using GC-RI and GC-MS analysis, the essential oils and the volatiles extracted from separated organs of <it>D. crinitus </it>Desf. were studied using HS-SPME.</p> <p>Results</p> <p>GC-RI and GC-MS analysis identified 72 and 79 components in oils extracted using HD and in the volatile fractions extracted using SPME, respectively. Two types of essential oils were produced by the plant: the root oils had aliphatic compounds as the main component (87.0%-90.1%), and the aerial part oils had phenylpropanoids as the main component (43.1%-88.6%). HS-SPME analysis showed a more precise distribution of compounds in the organs studied: oxygenated aliphatic compounds were well represented in the roots (44.3%-84.0%), hydrocarbon aliphatic compounds were in the leaves and stems (22.2%-87.9%), and phenylpropanoids were in the flowers and umbels (47.9%-64.2%). Moreover, HS-SPME allowed the occurrence of isochavicol (29.6 - 34.7%) as main component in <it>D. crinitus </it>leaves, but it was not detected in the oils, probably because of its solubility in water.</p> <p>Conclusions</p> <p>This study demonstrates that HD and HS-SPME modes could be complimentary extraction techniques in order to obtain the complete characterization of plant volatiles.</p

Identification of chrysanthenyl esters from Anthemis maritima essential oils investigated by GC-RI, GC/MS (EI and CI) and 13C-NMR spectroscopy. Chemical composition and variability

International audienceAnalysis of chemical compositions of 18 oil samples of Anthemis maritima L. essential oils from Corsica and Sardinia were investigated by GC, GC-MS and NMR. Integrated analysis allowed the identification of 124 components which accounted for 83.3 % to 91.6 % of the total amount. Principal components analysis established the occurrence of two clusters. The former cluster enclosed oil samples dominated by trans-chrysanthenyl acetate (34.9 - 68.5 %) while the latter cluster enclosed oil samples which exhibited 6-methyl-5-hepten-2-one (5.7 - 24.9 %) and cis-chrysanthenyl 2-methylbutyrate (3.2 - 15.4 %) as main components. The essential oils were dominated by oxygenated monoterpenes (16.4 - 81.8 %). Among them, 16 chrysanthenyl esters (10.8 - 74.5 %) were identified, 12 were laboratory-prepared and for the first time their 13C-NMR data and the 1H-NMR data of 7 of them were reported

Volatile Constituents of the Corsican liverwort Frullania tamarisci

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Etude chimique et biologique des huiles essentielles de Zanthoxylum zanthoxyloides (LAM.) du Sénégal

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Essential Oil composition and volatile constituents of Adenostyles briquetii Gamisans (syn. Cacalia briquetii)

International audienceThe essential oil of Adenostyles briquetii Gamisans (syn. Cacalia briquetii; family Asteraceae), an endemic species from Corsica, has been studied by GC (retention indices), GC/MS(EI and CI) and 13C-NMR. Thus, 142 components were identified representing 93% of the total amount. The essential oil was characterized by sesquiterpene hydrocarbons (52.8%) and oxygenated sesquiterpenes (25.9%). The major components were germacrene D (18.5%), zingiberene (12.9%) and -oplopenone (10.8%). In this study, the non terpenic esters of the oil have been investigated by GC/MS in different ionization modes: electron impact (EI), positive and negative chemical ionization (PCI and NCI) using ammonia as reagent gas. Furthermore, the analysis of volatile fraction of this plant was carried out using headspace-SPME and showed zingiberene, germacrene D, -elemene as the main components. To our knowledge, this work is the first report on the essential oil composition and on the volatile constituents of Adenostyles briquetii