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  • Proceedings of the National Academy of Sciences  (19)
  • Natural Sciences  (19)
  • 1
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    Online Resource
    Genetic regulatory signatures underlying islet gene expression and type 2 diabetes
    Proceedings of the National Academy of Sciences ; 2017
    In:  Proceedings of the National Academy of Sciences Vol. 114, No. 9 ( 2017-02-28), p. 2301-2306
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 114, No. 9 ( 2017-02-28), p. 2301-2306
    Abstract: Genome-wide association studies (GWAS) have identified 〉 100 independent SNPs that modulate the risk of type 2 diabetes (T2D) and related traits. However, the pathogenic mechanisms of most of these SNPs remain elusive. Here, we examined genomic, epigenomic, and transcriptomic profiles in human pancreatic islets to understand the links between genetic variation, chromatin landscape, and gene expression in the context of T2D. We first integrated genome and transcriptome variation across 112 islet samples to produce dense cis -expression quantitative trait loci ( cis -eQTL) maps. Additional integration with chromatin-state maps for islets and other diverse tissue types revealed that cis -eQTLs for islet-specific genes are specifically and significantly enriched in islet stretch enhancers. High-resolution chromatin accessibility profiling using assay for transposase-accessible chromatin sequencing (ATAC-seq) in two islet samples enabled us to identify specific transcription factor (TF) footprints embedded in active regulatory elements, which are highly enriched for islet cis -eQTL. Aggregate allelic bias signatures in TF footprints enabled us de novo to reconstruct TF binding affinities genetically, which support the high-quality nature of the TF footprint predictions. Interestingly, we found that T2D GWAS loci were strikingly and specifically enriched in islet Regulatory Factor X (RFX) footprints. Remarkably, within and across independent loci, T2D risk alleles that overlap with RFX footprints uniformly disrupt the RFX motifs at high-information content positions. Together, these results suggest that common regulatory variations have shaped islet TF footprints and the transcriptome and that a confluent RFX regulatory grammar plays a significant role in the genetic component of T2D predisposition.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1621192114
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2017
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  • 2
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    Coupling between oxidation state and hydrogen bond conformation in heme proteins
    Proceedings of the National Academy of Sciences ; 1979
    In:  Proceedings of the National Academy of Sciences Vol. 76, No. 3 ( 1979-03), p. 1009-1013
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 76, No. 3 ( 1979-03), p. 1009-1013
    Abstract: In all heme proteins for which crystal structures are available, the N ε of a histidyl residue is bonded to the heme iron and N δ is hydrogen bonded to a carbonyl oxygen of the peptide backbone. We investigate here the possibility that a change in oxidation state of the iron or a change in the geometry of this hydrogen bond might change the hydrogen bond strength in a functionally significant way. Dimerization energies obtained from ab initio molecular orbital calculations on the hydrogen-bonded dimer of imidazole and planar formamide are used to represent the strength of this hydrogen bond in heme proteins. The effect of a change in iron oxidation state is modeled by varying the positive charge on imidazole. The effect of a change in hydrogen bond geometry is studied by employing x-ray coordinates for reduced and oxidized cytochrome c , deoxy- and metmyoglobin, and deoxy- and methemoglobin. Our conclusions are that the strength of this hydrogen bond in heme proteins is sensitive to both the oxidation state of the iron atom and to geometry changes on the order of those obtained from the x-ray coordinates. We speculate that the changes in oxidation state may be functionally coupled with changes in hydrogen bond geometry and that this hydrogen bond represents a feasible pathway to link protein conformation with redox potential or reactivity of the iron atom.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.76.3.1009
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1979
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  • 3
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    Global fishery prospects under contrasting management regimes
    Proceedings of the National Academy of Sciences ; 2016
    In:  Proceedings of the National Academy of Sciences Vol. 113, No. 18 ( 2016-05-03), p. 5125-5129
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 113, No. 18 ( 2016-05-03), p. 5125-5129
    Abstract: Data from 4,713 fisheries worldwide, representing 78% of global reported fish catch, are analyzed to estimate the status, trends, and benefits of alternative approaches to recovering depleted fisheries. For each fishery, we estimate current biological status and forecast the impacts of contrasting management regimes on catch, profit, and biomass of fish in the sea. We estimate unique recovery targets and trajectories for each fishery, calculate the year-by-year effects of alternative recovery approaches, and model how alternative institutional reforms affect recovery outcomes. Current status is highly heterogeneous—the median fishery is in poor health (overfished, with further overfishing occurring), although 32% of fisheries are in good biological, although not necessarily economic, condition. Our business-as-usual scenario projects further divergence and continued collapse for many of the world’s fisheries. Applying sound management reforms to global fisheries in our dataset could generate annual increases exceeding 16 million metric tons (MMT) in catch, $53 billion in profit, and 619 MMT in biomass relative to business as usual. We also find that, with appropriate reforms, recovery can happen quickly, with the median fishery taking under 10 y to reach recovery targets. Our results show that commonsense reforms to fishery management would dramatically improve overall fish abundance while increasing food security and profits.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1520420113
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2016
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  • 4
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    Global change effects on plant communities are magnified by time and the number of global change factors imposed
    Proceedings of the National Academy of Sciences ; 2019
    In:  Proceedings of the National Academy of Sciences Vol. 116, No. 36 ( 2019-09-03), p. 17867-17873
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 116, No. 36 ( 2019-09-03), p. 17867-17873
    Abstract: Global change drivers (GCDs) are expected to alter community structure and consequently, the services that ecosystems provide. Yet, few experimental investigations have examined effects of GCDs on plant community structure across multiple ecosystem types, and those that do exist present conflicting patterns. In an unprecedented global synthesis of over 100 experiments that manipulated factors linked to GCDs, we show that herbaceous plant community responses depend on experimental manipulation length and number of factors manipulated. We found that plant communities are fairly resistant to experimentally manipulated GCDs in the short term ( 〈 10 y). In contrast, long-term (≥10 y) experiments show increasing community divergence of treatments from control conditions. Surprisingly, these community responses occurred with similar frequency across the GCD types manipulated in our database. However, community responses were more common when 3 or more GCDs were simultaneously manipulated, suggesting the emergence of additive or synergistic effects of multiple drivers, particularly over long time periods. In half of the cases, GCD manipulations caused a difference in community composition without a corresponding species richness difference, indicating that species reordering or replacement is an important mechanism of community responses to GCDs and should be given greater consideration when examining consequences of GCDs for the biodiversity–ecosystem function relationship. Human activities are currently driving unparalleled global changes worldwide. Our analyses provide the most comprehensive evidence to date that these human activities may have widespread impacts on plant community composition globally, which will increase in frequency over time and be greater in areas where communities face multiple GCDs simultaneously.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1819027116
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2019
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  • 5
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    Integrative analysis of gene expression, DNA methylation, physiological traits, and genetic variation in human skeletal muscle
    Proceedings of the National Academy of Sciences ; 2019
    In:  Proceedings of the National Academy of Sciences Vol. 116, No. 22 ( 2019-05-28), p. 10883-10888
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 116, No. 22 ( 2019-05-28), p. 10883-10888
    Abstract: We integrate comeasured gene expression and DNA methylation (DNAme) in 265 human skeletal muscle biopsies from the FUSION study with 〉 7 million genetic variants and eight physiological traits: height, waist, weight, waist–hip ratio, body mass index, fasting serum insulin, fasting plasma glucose, and type 2 diabetes. We find hundreds of genes and DNAme sites associated with fasting insulin, waist, and body mass index, as well as thousands of DNAme sites associated with gene expression (eQTM). We find that controlling for heterogeneity in tissue/muscle fiber type reduces the number of physiological trait associations, and that long-range eQTMs ( 〉 1 Mb) are reduced when controlling for tissue/muscle fiber type or latent factors. We map genetic regulators (quantitative trait loci; QTLs) of expression (eQTLs) and DNAme (mQTLs). Using Mendelian randomization (MR) and mediation techniques, we leverage these genetic maps to predict 213 causal relationships between expression and DNAme, approximately two-thirds of which predict methylation to causally influence expression. We use MR to integrate FUSION mQTLs, FUSION eQTLs, and GTEx eQTLs for 48 tissues with genetic associations for 534 diseases and quantitative traits. We identify hundreds of genes and thousands of DNAme sites that may drive the reported disease/quantitative trait genetic associations. We identify 300 gene expression MR associations that are present in both FUSION and GTEx skeletal muscle and that show stronger evidence of MR association in skeletal muscle than other tissues, which may partially reflect differences in power across tissues. As one example, we find that increased RXRA muscle expression may decrease lean tissue mass.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1814263116
    RVK:
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2019
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    detail.hit.zdb_id: 1461794-8
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  • 6
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    Helical structure, stability, and dynamics in human apolipoprotein E3 and E4 by hydrogen exchange and mass spectrometry
    Proceedings of the National Academy of Sciences ; 2017
    In:  Proceedings of the National Academy of Sciences Vol. 114, No. 5 ( 2017-01-31), p. 968-973
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 114, No. 5 ( 2017-01-31), p. 968-973
    Abstract: Apolipoprotein E (apoE) plays a critical role in cholesterol transport in both peripheral circulation and brain. Human apoE is a polymorphic 299-residue protein in which the less common E4 isoform differs from the major E3 isoform only by a C112R substitution. ApoE4 interacts with lipoprotein particles and with the amyloid-β peptide, and it is associated with increased incidence of cardiovascular and Alzheimer’s disease. To understand the structural basis for the differences between apoE3 and E4 functionality, we used hydrogen−deuterium exchange coupled with a fragment separation method and mass spectrometric analysis to compare their secondary structures at near amino acid resolution. We determined the positions, dynamics, and stabilities of the helical segments in these two proteins, in their normal tetrameric state and in mutation-induced monomeric mutants. Consistent with prior X-ray crystallography and NMR results, the N-terminal domain contains four α-helices, 20 to 30 amino acids long. The C-terminal domain is relatively unstructured in the monomeric state but forms an α-helix ∼70 residues long in the self-associated tetrameric state. Helix stabilities are relatively low, 4 kcal/mol to 5 kcal/mol, consistent with flexibility and facile reversible unfolding. Secondary structure in the tetrameric apoE3 and E4 isoforms is similar except that some helical segments in apoE4 spanning residues 12 to 20 and 204 to 210 are unfolded. These conformational differences result from the C112R substitution in the N-terminal helix bundle and likely relate to a reduced ability of apoE4 to form tetramers, thereby increasing the concentration of functional apoE4 monomers, which gives rise to its higher lipid binding compared with apoE3.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1617523114
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2017
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  • 7
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    Origin of long lifetime of band-edge charge carriers in organic–inorganic lead iodide perovskites
    Proceedings of the National Academy of Sciences ; 2017
    In:  Proceedings of the National Academy of Sciences Vol. 114, No. 29 ( 2017-07-18), p. 7519-7524
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 114, No. 29 ( 2017-07-18), p. 7519-7524
    Abstract: Long carrier lifetime is what makes hybrid organic–inorganic perovskites high-performance photovoltaic materials. Several microscopic mechanisms behind the unusually long carrier lifetime have been proposed, such as formation of large polarons, Rashba effect, ferroelectric domains, and photon recycling. Here, we show that the screening of band-edge charge carriers by rotation of organic cation molecules can be a major contribution to the prolonged carrier lifetime. Our results reveal that the band-edge carrier lifetime increases when the system enters from a phase with lower rotational entropy to another phase with higher entropy. These results imply that the recombination of the photoexcited electrons and holes is suppressed by the screening, leading to the formation of polarons and thereby extending the lifetime. Thus, searching for organic–inorganic perovskites with high rotational entropy over a wide range of temperature may be a key to achieve superior solar cell performance.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1704421114
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2017
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  • 8
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    Helical structure and stability in human apolipoprotein A-I by hydrogen exchange and mass spectrometry
    Proceedings of the National Academy of Sciences ; 2009
    In:  Proceedings of the National Academy of Sciences Vol. 106, No. 45 ( 2009-11-10), p. 19005-19010
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 106, No. 45 ( 2009-11-10), p. 19005-19010
    Abstract: Apolipoprotein A-I (apoA-I) stabilizes anti-atherogenic high density lipoprotein particles (HDL) in the circulation and governs their biogenesis, metabolism, and functional interactions. To decipher these important structure–function relationships, it will be necessary to understand the structure, stability, and plasticity of the apoA-I molecule. Biophysical studies show that lipid-free apoA-I contains a large amount of α-helical structure but the location of this structure and its properties are not established. We used hydrogen-deuterium exchange coupled with a fragmentation-separation method and mass spectrometric analysis to study human lipid-free apoA-I in its physiologically pertinent monomeric form. The acquisition of ≈100 overlapping peptide fragments that redundantly cover the 243-residue apoA-I polypeptide made it possible to define the positions and stabilities of helical segments and to draw inferences about their interactions and dynamic properties. Residues 7–44, 54–65, 70–78, 81–115, and 147–178 form α-helices, accounting for a helical content of 48 ± 3%, in agreement with circular dichroism measurements (49%). At 3 to 5 kcal/mol in free energy of stabilization, the helices are far more stable than could be achieved in isolation, indicating mutually stabilizing helix bundle interactions. However the helical structure is dynamic, unfolding and refolding in seconds, allowing facile apoA-I reorganization during HDL particle formation and remodeling.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0909708106
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2009
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  • 9
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    Saliva protein biomarkers to detect oral squamous cell carcinoma in a high-risk population in Taiwan
    Proceedings of the National Academy of Sciences ; 2016
    In:  Proceedings of the National Academy of Sciences Vol. 113, No. 41 ( 2016-10-11), p. 11549-11554
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 113, No. 41 ( 2016-10-11), p. 11549-11554
    Abstract: Most cases of oral squamous cell carcinoma (OSCC) develop from visible oral potentially malignant disorders (OPMDs). The latter exhibit heterogeneous subtypes with different transformation potentials, complicating the early detection of OSCC during routine visual oral cancer screenings. To develop clinically applicable biomarkers, we collected saliva samples from 96 healthy controls, 103 low-risk OPMDs, 130 high-risk OPMDs, and 131 OSCC subjects. These individuals were enrolled in Taiwan’s Oral Cancer Screening Program. We identified 302 protein biomarkers reported in the literature and/or through in-house studies and prioritized 49 proteins for quantification in the saliva samples using multiple reaction monitoring-MS. Twenty-eight proteins were successfully quantified with high confidence. The quantification data from non-OSCC subjects (healthy controls + low-risk OPMDs) and OSCC subjects in the training set were subjected to classification and regression tree analyses, through which we generated a four-protein panel consisting of MMP1, KNG1, ANXA2, and HSPA5. A risk-score scheme was established, and the panel showed high sensitivity (87.5%) and specificity (80.5%) in the test set to distinguish OSCC samples from non-OSCC samples. The risk score 〉 0.4 detected 84% (42/50) of the stage I OSCCs and a significant portion (42%) of the high-risk OPMDs. Moreover, among 88 high-risk OPMD patients with available follow-up results, 18 developed OSCC within 5 y; of them, 77.8% (14/18) had risk scores 〉 0.4. Our four-protein panel may therefore offer a clinically effective tool for detecting OSCC and monitoring high-risk OPMDs through a readily available biofluid.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1612368113
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2016
    detail.hit.zdb_id: 209104-5
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  • 10
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    High-resolution epitope mapping by HX MS reveals the pathogenic mechanism and a possible therapy for autoimmune TTP syndrome
    Proceedings of the National Academy of Sciences ; 2015
    In:  Proceedings of the National Academy of Sciences Vol. 112, No. 31 ( 2015-08-04), p. 9620-9625
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 112, No. 31 ( 2015-08-04), p. 9620-9625
    Abstract: Acquired thrombotic thrombocytopenic purpura (TTP), a thrombotic disorder that is fatal in almost all cases if not treated promptly, is primarily caused by IgG-type autoantibodies that inhibit the ability of the ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) metalloprotease to cleave von Willebrand factor (VWF). Because the mechanism of autoantibody-mediated inhibition of ADAMTS13 activity is not known, the only effective therapy so far is repeated whole-body plasma exchange. We used hydrogen–deuterium exchange mass spectrometry (HX MS) to determine the ADAMTS13 binding epitope for three representative human monoclonal autoantibodies, isolated from TTP patients by phage display as tethered single-chain fragments of the variable regions (scFvs). All three scFvs bind the same conformationally discontinuous epitopic region on five small solvent-exposed loops in the spacer domain of ADAMTS13. The same epitopic region is also bound by most polyclonal IgG autoantibodies in 23 TTP patients that we tested. The ability of ADAMTS13 to proteolyze VWF is impaired by the binding of autoantibodies at the epitopic loops in the spacer domain, by the deletion of individual epitopic loops, and by some local mutations. Structural considerations and HX MS results rule out any disruptive structure change effect in the distant ADAMTS13 metalloprotease domain. Instead, it appears that the same ADAMTS13 loop segments that bind the autoantibodies are also responsible for correct binding to the VWF substrate. If so, the autoantibodies must prevent VWF proteolysis simply by physically blocking normal ADAMTS13 to VWF interaction. These results point to the mechanism for autoantibody action and an avenue for therapeutic intervention.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1512561112
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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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