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  • 1
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    Organic-walled microfossils in 3.2-billion-year-old shallow-marine siliciclastic deposits (2010)
    Nature Publishing Group (NPG)
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    Publikationsdatum: 2010-02-09
    Beschreibung: Although the notion of an early origin and diversification of life on Earth during the Archaean eon has received increasing support in geochemical, sedimentological and palaeontological evidence, ambiguities and controversies persist regarding the biogenicity and syngeneity of the record older than Late Archaean. Non-biological processes are known to produce morphologies similar to some microfossils, and hydrothermal fluids have the potential to produce abiotic organic compounds with depleted carbon isotope values, making it difficult to establish unambiguous traces of life. Here we report the discovery of a population of large (up to about 300 mum in diameter) carbonaceous spheroidal microstructures in Mesoarchaean shales and siltstones of the Moodies Group, South Africa, the Earth's oldest siliciclastic alluvial to tidal-estuarine deposits. These microstructures are interpreted as organic-walled microfossils on the basis of petrographic and geochemical evidence for their endogenicity and syngeneity, their carbonaceous composition, cellular morphology and ultrastructure, occurrence in populations, taphonomic features of soft wall deformation, and the geological context plausible for life, as well as a lack of abiotic explanation falsifying a biological origin. These are the oldest and largest Archaean organic-walled spheroidal microfossils reported so far. Our observations suggest that relatively large microorganisms cohabited with earlier reported benthic microbial mats in the photic zone of marginal marine siliciclastic environments 3.2 billion years ago.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Javaux, Emmanuelle J -- Marshall, Craig P -- Bekker, Andrey -- England -- Nature. 2010 Feb 18;463(7283):934-8. doi: 10.1038/nature08793. Epub 2010 Feb 7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geology, University of Liege, 17 allee du 6 Aout B18, Liege 4000, Belgium. ej.javaux@ulg.ac.be〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20139963" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Acids ; Bacteria/chemistry/cytology/isolation & purification/metabolism ; Carbon/analysis/chemistry ; Carbon Isotopes ; *Ecosystem ; Eukaryotic Cells/chemistry/cytology ; *Fossils ; Geologic Sediments/*microbiology ; History, Ancient ; Oceans and Seas ; Organic Chemicals/*analysis/chemistry ; *Phylogeny ; Reproducibility of Results ; Seawater/*microbiology ; South Africa ; Spectrum Analysis, Raman ; Sunlight
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
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    The evolution of the marine phosphate reservoir (2010)
    Nature Publishing Group (NPG)
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    Publikationsdatum: 2010-10-29
    Beschreibung: Phosphorus is a biolimiting nutrient that has an important role in regulating the burial of organic matter and the redox state of the ocean-atmosphere system. The ratio of phosphorus to iron in iron-oxide-rich sedimentary rocks can be used to track dissolved phosphate concentrations if the dissolved silica concentration of sea water is estimated. Here we present iron and phosphorus concentration ratios from distal hydrothermal sediments and iron formations through time to study the evolution of the marine phosphate reservoir. The data suggest that phosphate concentrations have been relatively constant over the Phanerozoic eon, the past 542 million years (Myr) of Earth's history. In contrast, phosphate concentrations seem to have been elevated in Precambrian oceans. Specifically, there is a peak in phosphorus-to-iron ratios in Neoproterozoic iron formations dating from approximately 750 to approximately 635 Myr ago, indicating unusually high dissolved phosphate concentrations in the aftermath of widespread, low-latitude 'snowball Earth' glaciations. An enhanced postglacial phosphate flux would have caused high rates of primary productivity and organic carbon burial and a transition to more oxidizing conditions in the ocean and atmosphere. The snowball Earth glaciations and Neoproterozoic oxidation are both suggested as triggers for the evolution and radiation of metazoans. We propose that these two factors are intimately linked; a glacially induced nutrient surplus could have led to an increase in atmospheric oxygen, paving the way for the rise of metazoan life.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Planavsky, Noah J -- Rouxel, Olivier J -- Bekker, Andrey -- Lalonde, Stefan V -- Konhauser, Kurt O -- Reinhard, Christopher T -- Lyons, Timothy W -- England -- Nature. 2010 Oct 28;467(7319):1088-90. doi: 10.1038/nature09485.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth Sciences, University of California, Riverside, California 92521, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20981096" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Aquatic Organisms/*metabolism ; Atmosphere/chemistry ; *Biological Evolution ; Ferric Compounds/analysis/metabolism ; Geologic Sediments/chemistry ; History, Ancient ; Ice Cover ; Iron/analysis/metabolism ; Marine Biology ; Oceans and Seas ; Oxidation-Reduction ; Oxygen/analysis/metabolism ; Phosphates/analysis/*metabolism ; Phosphorus/analysis/metabolism ; Seawater/chemistry ; Silicon Dioxide/analysis/metabolism
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
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    Tracing the stepwise oxygenation of the Proterozoic ocean (2008)
    Nature Publishing Group (NPG)
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    Publikationsdatum: 2008-03-28
    Beschreibung: Biogeochemical signatures preserved in ancient sedimentary rocks provide clues to the nature and timing of the oxygenation of the Earth's atmosphere. Geochemical data suggest that oxygenation proceeded in two broad steps near the beginning and end of the Proterozoic eon (2,500 to 542 million years ago). The oxidation state of the Proterozoic ocean between these two steps and the timing of deep-ocean oxygenation have important implications for the evolutionary course of life on Earth but remain poorly known. Here we present a new perspective on ocean oxygenation based on the authigenic accumulation of the redox-sensitive transition element molybdenum in sulphidic black shales. Accumulation of authigenic molybdenum from sea water is already seen in shales by 2,650 Myr ago; however, the small magnitudes of these enrichments reflect weak or transient sources of dissolved molybdenum before about 2,200 Myr ago, consistent with minimal oxidative weathering of the continents. Enrichments indicative of persistent and vigorous oxidative weathering appear in shales deposited at roughly 2,150 Myr ago, more than 200 million years after the initial rise in atmospheric oxygen. Subsequent expansion of sulphidic conditions after about 1,800 Myr ago (refs 8, 9) maintained a mid-Proterozoic molybdenum reservoir below 20 per cent of the modern inventory, which in turn may have acted as a nutrient feedback limiting the spatiotemporal distribution of euxinic (sulphidic) bottom waters and perhaps the evolutionary and ecological expansion of eukaryotic organisms. By 551 Myr ago, molybdenum contents reflect a greatly expanded oceanic reservoir due to oxygenation of the deep ocean and corresponding decrease in sulphidic conditions in the sediments and water column.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Scott, C -- Lyons, T W -- Bekker, A -- Shen, Y -- Poulton, S W -- Chu, X -- Anbar, A D -- England -- Nature. 2008 Mar 27;452(7186):456-9. doi: 10.1038/nature06811.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth Sciences, University of California, Riverside, California 92521, USA. cscot002@ucr.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18368114" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere/chemistry ; Geologic Sediments/chemistry ; History, Ancient ; Molybdenum/analysis ; Oceans and Seas ; Oxygen/*analysis/chemistry ; Seawater/*chemistry ; Sulfides/chemistry ; Time Factors
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
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    Large colonial organisms with coordinated growth in oxygenated environments 2.1 Gyr ago (2010)
    Nature Publishing Group (NPG)
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    Publikationsdatum: 2010-07-03
    Beschreibung: The evidence for macroscopic life during the Palaeoproterozoic era (2.5-1.6 Gyr ago) is controversial. Except for the nearly 2-Gyr-old coil-shaped fossil Grypania spiralis, which may have been eukaryotic, evidence for morphological and taxonomic biodiversification of macroorganisms only occurs towards the beginning of the Mesoproterozoic era (1.6-1.0 Gyr). Here we report the discovery of centimetre-sized structures from the 2.1-Gyr-old black shales of the Palaeoproterozoic Francevillian B Formation in Gabon, which we interpret as highly organized and spatially discrete populations of colonial organisms. The structures are up to 12 cm in size and have characteristic shapes, with a simple but distinct ground pattern of flexible sheets and, usually, a permeating radial fabric. Geochemical analyses suggest that the sediments were deposited under an oxygenated water column. Carbon and sulphur isotopic data indicate that the structures were distinct biogenic objects, fossilized by pyritization early in the formation of the rock. The growth patterns deduced from the fossil morphologies suggest that the organisms showed cell-to-cell signalling and coordinated responses, as is commonly associated with multicellular organization. The Gabon fossils, occurring after the 2.45-2.32-Gyr increase in atmospheric oxygen concentration, may be seen as ancient representatives of multicellular life, which expanded so rapidly 1.5 Gyr later, in the Cambrian explosion.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉El Albani, Abderrazak -- Bengtson, Stefan -- Canfield, Donald E -- Bekker, Andrey -- Macchiarelli, Roberto -- Mazurier, Arnaud -- Hammarlund, Emma U -- Boulvais, Philippe -- Dupuy, Jean-Jacques -- Fontaine, Claude -- Fursich, Franz T -- Gauthier-Lafaye, Francois -- Janvier, Philippe -- Javaux, Emmanuelle -- Ossa, Frantz Ossa -- Pierson-Wickmann, Anne-Catherine -- Riboulleau, Armelle -- Sardini, Paul -- Vachard, Daniel -- Whitehouse, Martin -- Meunier, Alain -- England -- Nature. 2010 Jul 1;466(7302):100-4. doi: 10.1038/nature09166.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratoire HYDRASA, UMR 6269 CNRS-INSU, Universite de Poitiers, 86022 Poitiers, France. abder.albani@univ-poitiers.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20596019" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Bacteria/cytology ; *Ecosystem ; Eukaryota/cytology ; *Fossils ; Gabon ; Geologic Sediments/microbiology ; History, Ancient ; Oxygen/*metabolism
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
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    Widespread iron-rich conditions in the mid-Proterozoic ocean (2011)
    Nature Publishing Group (NPG)
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    Publikationsdatum: 2011-09-09
    Beschreibung: The chemical composition of the ocean changed markedly with the oxidation of the Earth's surface, and this process has profoundly influenced the evolutionary and ecological history of life. The early Earth was characterized by a reducing ocean-atmosphere system, whereas the Phanerozoic eon (less than 542 million years ago) is known for a stable and oxygenated biosphere conducive to the radiation of animals. The redox characteristics of surface environments during Earth's middle age (1.8-1 billion years ago) are less well known, but it is generally assumed that the mid-Proterozoic was home to a globally sulphidic (euxinic) deep ocean. Here we present iron data from a suite of mid-Proterozoic marine mudstones. Contrary to the popular model, our results indicate that ferruginous (anoxic and Fe(2+)-rich) conditions were both spatially and temporally extensive across diverse palaeogeographic settings in the mid-Proterozoic ocean, inviting new models for the temporal distribution of iron formations and the availability of bioessential trace elements during a critical window for eukaryotic evolution.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Planavsky, Noah J -- McGoldrick, Peter -- Scott, Clinton T -- Li, Chao -- Reinhard, Christopher T -- Kelly, Amy E -- Chu, Xuelei -- Bekker, Andrey -- Love, Gordon D -- Lyons, Timothy W -- England -- Nature. 2011 Sep 7;477(7365):448-51. doi: 10.1038/nature10327.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth Sciences, University of California, Riverside, California 92521, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21900895" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Biological Evolution ; Geologic Sediments/chemistry ; History, Ancient ; Iron/*analysis/chemistry ; Oceans and Seas ; Seawater/*chemistry ; Sulfur/analysis/chemistry ; Sulfur Isotopes ; Time Factors
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
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    DNA repair. Proteomics reveals dynamic assembly of repair complexes during bypass of DNA cross-links (2015)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 2015-05-02
    Beschreibung: DNA interstrand cross-links (ICLs) block replication fork progression by inhibiting DNA strand separation. Repair of ICLs requires sequential incisions, translesion DNA synthesis, and homologous recombination, but the full set of factors involved in these transactions remains unknown. We devised a technique called chromatin mass spectrometry (CHROMASS) to study protein recruitment dynamics during perturbed DNA replication in Xenopus egg extracts. Using CHROMASS, we systematically monitored protein assembly and disassembly on ICL-containing chromatin. Among numerous prospective DNA repair factors, we identified SLF1 and SLF2, which form a complex with RAD18 and together define a pathway that suppresses genome instability by recruiting the SMC5/6 cohesion complex to DNA lesions. Our study provides a global analysis of an entire DNA repair pathway and reveals the mechanism of SMC5/6 relocalization to damaged DNA in vertebrate cells.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Raschle, Markus -- Smeenk, Godelieve -- Hansen, Rebecca K -- Temu, Tikira -- Oka, Yasuyoshi -- Hein, Marco Y -- Nagaraj, Nagarjuna -- Long, David T -- Walter, Johannes C -- Hofmann, Kay -- Storchova, Zuzana -- Cox, Jurgen -- Bekker-Jensen, Simon -- Mailand, Niels -- Mann, Matthias -- HL098316/HL/NHLBI NIH HHS/ -- Howard Hughes Medical Institute/ -- New York, N.Y. -- Science. 2015 May 1;348(6234):1253671. doi: 10.1126/science.1253671. Epub 2015 Apr 30.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany. ; Ubiquitin Signaling Group, Department of Disease Biology, Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, DK-2200 Copenhagen, Denmark. ; Howard Hughes Medical Institute and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA. ; Institute of Genetics, University of Cologne, 50674 Cologne, Germany. ; Maintenance of Genome Stability Group, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany. ; Ubiquitin Signaling Group, Department of Disease Biology, Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, DK-2200 Copenhagen, Denmark. simon.bekker-jensen@cpr.ku.dk niels.mailand@cpr.ku.dk mmann@biochem.mpg.de. ; Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany. Novo Nordisk Foundation Center for Protein Research, Proteomics Program, University of Copenhagen, DK-2200 Copenhagen, Denmark. simon.bekker-jensen@cpr.ku.dk niels.mailand@cpr.ku.dk mmann@biochem.mpg.de.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25931565" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Chromatin/chemistry/metabolism ; *DNA Damage ; *DNA Repair ; DNA Repair Enzymes/*metabolism ; *DNA Replication ; DNA-Binding Proteins/metabolism ; Mass Spectrometry/methods ; Proteomics/methods ; RNA-Binding Proteins/metabolism ; Xenopus
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
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    Histone H1 couples initiation and amplification of ubiquitin signalling after DNA damage (2015)
    Nature Publishing Group (NPG)
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    Publikationsdatum: 2015-10-28
    Beschreibung: DNA double-strand breaks (DSBs) are highly cytotoxic DNA lesions that trigger non-proteolytic ubiquitylation of adjacent chromatin areas to generate binding sites for DNA repair factors. This depends on the sequential actions of the E3 ubiquitin ligases RNF8 and RNF168 (refs 1-6), and UBC13 (also known as UBE2N), an E2 ubiquitin-conjugating enzyme that specifically generates K63-linked ubiquitin chains. Whereas RNF168 is known to catalyse ubiquitylation of H2A-type histones, leading to the recruitment of repair factors such as 53BP1 (refs 8-10), the critical substrates of RNF8 and K63-linked ubiquitylation remain elusive. Here we elucidate how RNF8 and UBC13 promote recruitment of RNF168 and downstream factors to DSB sites in human cells. We establish that UBC13-dependent K63-linked ubiquitylation at DSB sites is predominantly mediated by RNF8 but not RNF168, and that H1-type linker histones, but not core histones, represent major chromatin-associated targets of this modification. The RNF168 module (UDM1) recognizing RNF8-generated ubiquitylations is a high-affinity reader of K63-ubiquitylated H1, mechanistically explaining the essential roles of RNF8 and UBC13 in recruiting RNF168 to DSBs. Consistently, reduced expression or chromatin association of linker histones impair accumulation of K63-linked ubiquitin conjugates and repair factors at DSB-flanking chromatin. These results identify histone H1 as a key target of RNF8-UBC13 in DSB signalling and expand the concept of the histone code by showing that posttranslational modifications of linker histones can serve as important marks for recognition by factors involved in genome stability maintenance, and possibly beyond.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Thorslund, Tina -- Ripplinger, Anita -- Hoffmann, Saskia -- Wild, Thomas -- Uckelmann, Michael -- Villumsen, Bine -- Narita, Takeo -- Sixma, Titia K -- Choudhary, Chunaram -- Bekker-Jensen, Simon -- Mailand, Niels -- England -- Nature. 2015 Nov 19;527(7578):389-93. doi: 10.1038/nature15401. Epub 2015 Oct 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Ubiquitin Signaling Group, Protein Signaling Program, The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark. ; Proteomics Program, The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark. ; Division of Biochemistry, Cancer Genomics Center, Netherlands Cancer Institute, 1066 CX Amsterdam, the Netherlands.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26503038" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chromatin/metabolism ; DNA Breaks, Double-Stranded ; *DNA Damage ; DNA Repair ; DNA-Binding Proteins/metabolism ; Histones/chemistry/*metabolism ; Humans ; Lysine/metabolism ; Protein Structure, Tertiary ; *Signal Transduction ; Ubiquitin/*metabolism ; Ubiquitin-Conjugating Enzymes/metabolism ; Ubiquitin-Protein Ligases/chemistry/metabolism ; Ubiquitination
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
    Standort Signatur Erwartet Verfügbarkeit
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