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  • 1
    Online Resource
    Online Resource
    Proceedings of the National Academy of Sciences ; 2021
    In:  Proceedings of the National Academy of Sciences Vol. 118, No. 45 ( 2021-11-09)
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 118, No. 45 ( 2021-11-09)
    Abstract: The Toba volcanic system in Indonesia has produced two of the largest eruptions ( 〉 2,000 km 3 dense-rock equivalent [DRE] each) on Earth since the Quaternary. U–Pb crystallization ages of zircon span a period of ∼600 ky before each eruptive event, and in the run-up to each eruption, the mean and variance of the zircons’ U content decrease. To quantify the process of accumulation of eruptible magma underneath the Toba caldera, we integrated these observations with thermal and geochemical modeling. We show that caldera-forming eruptions at Toba are the result of progressive thermal maturation of the upper crustal magma reservoir, which grows and chemically homogenizes, by sustained magma influx at average volumetric rates between 0.008 and 0.01 km 3 /y over the past 2.2 My. Protracted thermal pulses related to magma-recharge events prime the system for eruption without necessarily requiring an increased magma-recharge rate before the two supereruptions. If the rate of magma input was maintained since the last supereruption of Toba at 75 ka, eruptible magma is currently accumulating at a minimum rate of ∼4.2 km 3 per millennium, and the current estimate of the total volume of potentially eruptible magma available today is a minimum of ∼315 km 3 . Our approach to evaluate magma flux and the rate of eruptible magma accumulation is applicable to other volcanic systems capable of producing supereruptions and thereby could help in assessing the potential of active volcanic systems to feed supereruptions.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2021
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  • 2
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 117, No. 5 ( 2020-02-04), p. 2560-2569
    Abstract: De novo mutations (DNMs), or mutations that appear in an individual despite not being seen in their parents, are an important source of genetic variation whose impact is relevant to studies of human evolution, genetics, and disease. Utilizing high-coverage whole-genome sequencing data as part of the Trans-Omics for Precision Medicine (TOPMed) Program, we called 93,325 single-nucleotide DNMs across 1,465 trios from an array of diverse human populations, and used them to directly estimate and analyze DNM counts, rates, and spectra. We find a significant positive correlation between local recombination rate and local DNM rate, and that DNM rate explains a substantial portion (8.98 to 34.92%, depending on the model) of the genome-wide variation in population-level genetic variation from 41K unrelated TOPMed samples. Genome-wide heterozygosity does correlate with DNM rate, but only explains 〈 1% of variation. While we are underpowered to see small differences, we do not find significant differences in DNM rate between individuals of European, African, and Latino ancestry, nor across ancestrally distinct segments within admixed individuals. However, we did find significantly fewer DNMs in Amish individuals, even when compared with other Europeans, and even after accounting for parental age and sequencing center. Specifically, we found significant reductions in the number of C→A and T→C mutations in the Amish, which seem to underpin their overall reduction in DNMs. Finally, we calculated near-zero estimates of narrow sense heritability ( h 2 ), which suggest that variation in DNM rate is significantly shaped by nonadditive genetic effects and the environment.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2020
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  • 3
    Online Resource
    Online Resource
    Proceedings of the National Academy of Sciences ; 2018
    In:  Proceedings of the National Academy of Sciences Vol. 115, No. 18 ( 2018-05), p. 4719-4724
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 115, No. 18 ( 2018-05), p. 4719-4724
    Abstract: CRISPR/Cas9-based transcriptional activation (CRISPRa) has recently emerged as a powerful and scalable technique for systematic overexpression genetic analysis in Drosophila melanogaster . We present flySAM, a potent tool for in vivo CRISPRa, which offers major improvements over existing strategies in terms of effectiveness, scalability, and ease of use. flySAM outperforms existing in vivo CRISPRa strategies and approximates phenotypes obtained using traditional Gal4-UAS overexpression. Moreover, because flySAM typically requires only a single sgRNA, it dramatically improves scalability. We use flySAM to demonstrate multiplexed CRISPRa, which has not been previously shown in vivo. In addition, we have simplified the experimental use of flySAM by creating a single vector encoding both the UAS:Cas9-activator and the sgRNA, allowing for inducible CRISPRa in a single genetic cross. flySAM will replace previous CRISPRa strategies as the basis of our growing genome-wide transgenic overexpression resource, TRiP-OE.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2018
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  • 4
    Online Resource
    Online Resource
    Proceedings of the National Academy of Sciences ; 2016
    In:  Proceedings of the National Academy of Sciences Vol. 113, No. 15 ( 2016-04-12)
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 113, No. 15 ( 2016-04-12)
    Abstract: Notch controls skeletogenesis, but its role in the remodeling of adult bone remains conflicting. In mature mice, the skeleton can become osteopenic or osteosclerotic depending on the time point at which Notch is activated or inactivated. Using adult EGFP reporter mice, we find that Notch expression is localized to osteocytes embedded within bone matrix. Conditional activation of Notch signaling in osteocytes triggers profound bone formation, mainly due to increased mineralization, which rescues both age-associated and ovariectomy-induced bone loss and promotes bone healing following osteotomy. In parallel, mice rendered haploinsufficient in γ-secretase presenilin-1 (Psen1), which inhibits downstream Notch activation, display almost-absent terminal osteoblast differentiation. Consistent with this finding, pharmacologic or genetic disruption of Notch or its ligand Jagged1 inhibits mineralization. We suggest that stimulation of Notch signaling in osteocytes initiates a profound, therapeutically relevant, anabolic response.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2016
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  • 5
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 112, No. 11 ( 2015-03-17)
    Abstract: The development of efficient sequencing techniques has resulted in large numbers of genomes being available for evolutionary studies. However, only one genome is available for all amphibians, that of Xenopus tropicalis , which is distantly related from the majority of frogs. More than 96% of frogs belong to the Neobatrachia, and no genome exists for this group. This dearth of amphibian genomes greatly restricts genomic studies of amphibians and, more generally, our understanding of tetrapod genome evolution. To fill this gap, we provide the de novo genome of a Tibetan Plateau frog, Nanorana parkeri , and compare it to that of X. tropicalis and other vertebrates. This genome encodes more than 20,000 protein-coding genes, a number similar to that of Xenopus . Although the genome size of Nanorana is considerably larger than that of Xenopus (2.3 vs. 1.5 Gb), most of the difference is due to the respective number of transposable elements in the two genomes. The two frogs exhibit considerable conserved whole-genome synteny despite having diverged approximately 266 Ma, indicating a slow rate of DNA structural evolution in anurans. Multigenome synteny blocks further show that amphibians have fewer interchromosomal rearrangements than mammals but have a comparable rate of intrachromosomal rearrangements. Our analysis also identifies 11 Mb of anuran-specific highly conserved elements that will be useful for comparative genomic analyses of frogs. The Nanorana genome offers an improved understanding of evolution of tetrapod genomes and also provides a genomic reference for other evolutionary studies.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2015
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  • 6
    Online Resource
    Online Resource
    American Association for the Advancement of Science (AAAS) ; 2014
    In:  Science Vol. 344, No. 6182 ( 2014-04-25), p. 376-380
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 344, No. 6182 ( 2014-04-25), p. 376-380
    Abstract: The hierarchical packaging of eukaryotic chromatin plays a central role in transcriptional regulation and other DNA-related biological processes. Here, we report the 11-angstrom–resolution cryogenic electron microscopy (cryo-EM) structures of 30-nanometer chromatin fibers reconstituted in the presence of linker histone H1 and with different nucleosome repeat lengths. The structures show a histone H1-dependent left-handed twist of the repeating tetranucleosomal structural units, within which the four nucleosomes zigzag back and forth with a straight linker DNA. The asymmetric binding and the location of histone H1 in chromatin play a role in the formation of the 30-nanometer fiber. Our results provide mechanistic insights into how nucleosomes compact into higher-order chromatin fibers.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
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    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2014
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  • 7
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 116, No. 3 ( 2019-01-15), p. 890-899
    Abstract: The AML1-ETO fusion protein, generated by the t(8;21) chromosomal translocation, is causally involved in nearly 20% of acute myeloid leukemia (AML) cases. In leukemic cells, AML1-ETO resides in and functions through a stable protein complex, AML1-ETO–containing transcription factor complex (AETFC), that contains multiple transcription (co)factors. Among these AETFC components, HEB and E2A, two members of the ubiquitously expressed E proteins, directly interact with AML1-ETO, confer new DNA-binding capacity to AETFC, and are essential for leukemogenesis. However, the third E protein, E2-2, is specifically silenced in AML1-ETO–expressing leukemic cells, suggesting E2-2 as a negative factor of leukemogenesis. Indeed, ectopic expression of E2-2 selectively inhibits the growth of AML1-ETO–expressing leukemic cells, and this inhibition requires the bHLH DNA-binding domain. RNA-seq and ChIP-seq analyses reveal that, despite some overlap, the three E proteins differentially regulate many target genes. In particular, studies show that E2-2 both redistributes AETFC to, and activates, some genes associated with dendritic cell differentiation and represses MYC target genes. In AML patients, the expression of E2-2 is relatively lower in the t(8;21) subtype, and an E2-2 target gene, THPO , is identified as a potential predictor of relapse. In a mouse model of human t(8;21) leukemia, E2-2 suppression accelerates leukemogenesis. Taken together, these results reveal that, in contrast to HEB and E2A, which facilitate AML1-ETO–mediated leukemogenesis, E2-2 compromises the function of AETFC and negatively regulates leukemogenesis. The three E proteins thus define a heterogeneity of AETFC, which improves our understanding of the precise mechanism of leukemogenesis and assists development of diagnostic/therapeutic strategies.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2019
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  • 8
    Online Resource
    Online Resource
    Proceedings of the National Academy of Sciences ; 2022
    In:  Proceedings of the National Academy of Sciences Vol. 119, No. 50 ( 2022-12-13)
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 119, No. 50 ( 2022-12-13)
    Abstract: Mammalian reovirus (reovirus) is a multilayered, turreted member of Reoviridae characterized by transcription of dsRNA genome within the innermost capsid shell. Here, we present high-resolution in situ structures of reovirus transcriptase complex in an intact double-layered virion, and in the uncoated single-layered core particles in the unloaded, reloaded, pre-elongation, and elongation states, respectively, obtained by cryo-electron microscopy and sub-particle reconstructions. At the template entry of RNA-dependent RNA polymerase (RdRp), the RNA-loading region gets flexible after uncoating resulting in the unloading of terminal genomic RNA and inactivity of transcription. However, upon adding transcriptional substrates, the RNA-loading region is recovered leading the RNAs loaded again. The priming loop in RdRp was found to play a critical role in regulating transcription, which hinders the elongation of transcript in virion and triggers the rearrangement of RdRp C-terminal domain (CTD) during elongation, resulting in splitting of template-transcript hybrid and opening of transcript exit. With the integration of these structures, a transcriptional model of reovirus with five states is proposed. Our structures illuminate the RdRp activation and regulation of the multilayered turreted reovirus.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2022
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  • 9
    Online Resource
    Online Resource
    Proceedings of the National Academy of Sciences ; 2015
    In:  Proceedings of the National Academy of Sciences Vol. 112, No. 45 ( 2015-11-10), p. 13988-13993
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 112, No. 45 ( 2015-11-10), p. 13988-13993
    Abstract: Dynamic regulation of chromatin structure is required to modulate the transcription of genes in eukaryotes. However, the factors that contribute to the plasticity of heterochromatin structure are elusive. Here, we report that cyclin-dependent kinase 12 (CDK12), a transcription elongation-associated RNA polymerase II (RNAPII) kinase, antagonizes heterochromatin enrichment in Drosophila chromosomes. Notably, loss of CDK12 induces the ectopic accumulation of heterochromatin protein 1 (HP1) on euchromatic arms, with a prominent enrichment on the X chromosome. Furthermore, ChIP and sequencing analysis reveals that the heterochromatin enrichment on the X chromosome mainly occurs within long genes involved in neuronal functions. Consequently, heterochromatin enrichment reduces the transcription of neuronal genes in the adult brain and results in a defect in Drosophila courtship learning. Taken together, these results define a previously unidentified role of CDK12 in controlling the epigenetic transition between euchromatin and heterochromatin and suggest a chromatin regulatory mechanism in neuronal behaviors.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2015
    detail.hit.zdb_id: 209104-5
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    SSG: 12
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  • 10
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 379, No. 6637 ( 2023-03-17)
    Abstract: Autoimmune diseases such as ankylosing spondylitis (AS) can be caused by emerging neoantigens that break immune tolerance in humans. Posttranslational modifications (PTMs) have been shown to be a critical mechanism that alters protein structure and function to generate neoantigens and induce subsequent autoimmune responses. Previous studies have confirmed that citrulline-modified peptides are a critical source of neoantigens in rheumatoid arthritis. However, the molecular mechanisms underlying neoantigen formation and pathogenic autoreactive responses for AS are largely unknown. There is an urgent need to develop a systematic approach to profiling the possible PTMs in patients with AS and identifying AS-associated PTMs responsible for autoreactive neoantigen production to better understand the etiology of autoimmune diseases. RATIONALE AS has been suggested to be an autoimmune disease because of its clear correlation with certain major histocompatibility complex (MHC) alleles, including HLA-B27. Neoantigens have been hypothesized to induce an aberrant immune response, leading to pathogenic autoreactive T cell responses and autoantibody generation in AS. Here, we developed a systematic open search approach to identify any possible amino acid residues and derivatives in the proteins that are different from the genomic coding sequences. We then applied this information to identify AS-related neoantigens with PTMs within a possible pool of PTM autoantigens and elucidate the pathogenesis of AS. RESULTS An open search approach was applied to identify any possible amino acid derivatives across the proteome of patients with AS. This approach generated a large set of noncoded amino acids representing the mass differences between the coded amino acids and actual residues. Among these, an amino acid derivative with a delta mass of 72.021 showed the greatest increase in patients with AS and resulted from a PTM called cysteine carboxyethylation. In vitro and in vivo experiments demonstrated that carboxyethylation at a cysteine residue of integrin αIIb [ITGA2B (CD41)] was catalyzed by cystathionine beta synthase (CBS) in a process that required 3-hydroxypropionic acid (3-HPA), a metabolite commonly released from gut microbes. Cysteine carboxyethylation induced the lysosomal degradation of ITGA2B and produced neoantigens that triggered MHC-II–dependent CD4 + T cell responses. Fluorescence polarization and enzyme-linked immunosorbent assay (ELISA) demonstrated that the identified carboxyethylated peptide (ITGA2B-ceC96) specifically interacted with HLA-DRA*01/HLA-DRB1*04 and was associated with autoantibody production and T cell responses in HLA-DRB1*04 patients. Additional in vitro assays showed that the neoantigen ITGA2B-ceC96 correlated with 3-HPA levels but was independent of CBS expression. HLA-DRB1 haplotype, the carboxyethylated peptide, specific autoantibodies, and 3-HPA levels in patients with AS all correlated with one another. 3-HPA–treated and ITGA2B-ceC96–immunized HLA-DR4 transgenic mice developed colitis and vertebral bone erosion. Thus, cysteine carboxyethylation induced by the metabolite 3-HPA generates a neoantigen that appears to be critical for autoimmune responses in patients with AS. CONCLUSION Cysteine carboxyethylation is an in vivo protein modification induced by the metabolite 3-HPA, which is commonly released from gut microbes. Carboxyethylated ITGA2B then induces autoantibody production and autoimmune response in AS. Our work provides a systematic workflow to identify differentially modified proteins that are important for neoantigen production in immune disorders. This approach furthers our understanding of AS pathogenesis and may aid in the development of neoantigen-based diagnosis and treatment for AS and other autoimmune diseases. Metabolite-induced cysteine carboxyethylation provokes HLA-restricted autoimmune responses in ankylosing spondylitis. 3-HPA, which is commonly obtained from food and gut microbes, induces carboxyethylation of cysteine residues in integrin αIIb (ITGA2B). Cysteine carboxyethylation requires CBS, and carboxyethylated ITGA2B (ITGA2B-ceC96) peptides are recruited to the HLA-DR4 complex and thereby stimulate CD4 + T cell responses closely related to AS.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
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    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2023
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    SSG: 11
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