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Preview: PNAS - RSS feed of Early Edition articles

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Proceedings of the National Academy of Sciences RSS feed -- Early Edition



 



Future urban land expansion and implications for global croplands [Sustainability Science]

2016-12-27T09:51:19-08:00

Urban expansion often occurs on croplands. However, there is little scientific understanding of how global patterns of future urban expansion will affect the world’s cultivated areas. Here, we combine spatially explicit projections of urban expansion with datasets on global croplands and crop yields. Our results show that urban expansion will...



Global urban signatures of phenotypic change in animal and plant populations [Sustainability Science]

2017-01-03T08:47:11-08:00

Humans challenge the phenotypic, genetic, and cultural makeup of species by affecting the fitness landscapes on which they evolve. Recent studies show that cities might play a major role in contemporary evolution by accelerating phenotypic changes in wildlife, including animals, plants, fungi, and other organisms. Many studies of ecoevolutionary change...



Urban sustainability in an age of enduring inequalities: Advancing theory and ecometrics for the 21st-century city [Perspectives]

2017-01-06T12:50:12-08:00

The environmental fragility of cities under advanced urbanization has motivated extensive efforts to promote the sustainability of urban ecosystems and physical infrastructures. Less attention has been devoted to neighborhood inequalities and fissures in the civic infrastructure that potentially challenge social sustainability and the capacity of cities to collectively address environmental...



Global scenarios of urban density and its impacts on building energy use through 2050 [Sustainability Science]

2017-01-09T12:10:28-08:00

Although the scale of impending urbanization is well-acknowledged, we have a limited understanding of how urban forms will change and what their impact will be on building energy use. Using both top-down and bottom-up approaches and scenarios, we examine building energy use for heating and cooling. Globally, the energy use...



EHD2 restrains dynamics of caveolae by an ATP-dependent, membrane-bound, open conformation [Biochemistry]

2017-02-21T10:14:29-08:00

The EH-domain–containing protein 2 (EHD2) is a dynamin-related ATPase that confines caveolae to the cell surface by restricting the scission and subsequent endocytosis of these membrane pits. For this, EHD2 is thought to first bind to the membrane, then to oligomerize, and finally to detach, in a stringently regulated mechanistic...



Structural insights into the activation mechanism of dynamin-like EHD ATPases [Biophysics and Computational Biology]

2017-02-22T11:34:28-08:00

Eps15 (epidermal growth factor receptor pathway substrate 15)-homology domain containing proteins (EHDs) comprise a family of dynamin-related mechano-chemical ATPases involved in cellular membrane trafficking. Previous studies have revealed the structure of the EHD2 dimer, but the molecular mechanisms of membrane recruitment and assembly have remained obscure. Here, we determined the...



Cas1 and the Csy complex are opposing regulators of Cas2/3 nuclease activity [Biochemistry]

2017-04-24T11:56:07-07:00

The type I-F CRISPR adaptive immune system in Pseudomonas aeruginosa (PA14) consists of two CRISPR loci and six CRISPR-associated (cas) genes. Type I-F systems rely on a CRISPR RNA (crRNA)-guided surveillance complex (Csy complex) to bind foreign DNA and recruit a trans-acting nuclease (i.e., Cas2/3) for target degradation. In most...



Effects of habitat disturbance on tropical forest biodiversity [Ecology]

2017-05-01T12:09:27-07:00

It is widely expected that habitat destruction in the tropics will cause a mass extinction in coming years, but the potential magnitude of the loss is unclear. Existing literature has focused on estimating global extinction rates indirectly or on quantifying effects only at local and regional scales. This paper directly...



Heterogeneity and scale of sustainable development in cities [Sustainability Science]

2017-05-01T12:09:28-07:00

Rapid worldwide urbanization is at once the main cause and, potentially, the main solution to global sustainable development challenges. The growth of cities is typically associated with increases in socioeconomic productivity, but it also creates strong inequalities. Despite a growing body of evidence characterizing these heterogeneities in developed urban areas,...



Multiscale model predicts increasing focal adhesion size with decreasing stiffness in fibrous matrices [Biophysics and Computational Biology]

2017-05-03T12:17:34-07:00

We describe a multiscale model that incorporates force-dependent mechanical plasticity induced by interfiber cross-link breakage and stiffness-dependent cellular contractility to predict focal adhesion (FA) growth and mechanosensing in fibrous extracellular matrices (ECMs). The model predicts that FA size depends on both the stiffness of ECM and the density of ligands...



Altered interactions between unicellular and multicellular genes drive hallmarks of transformation in a diverse range of solid tumors [Systems Biology]

2017-05-08T11:57:41-07:00

Tumors of distinct tissues of origin and genetic makeup display common hallmark cellular phenotypes, including sustained proliferation, suppression of cell death, and altered metabolism. These phenotypic commonalities have been proposed to stem from disruption of conserved regulatory mechanisms evolved during the transition to multicellularity to control fundamental cellular processes such...



Bam-dependent deubiquitinase complex can disrupt germ-line stem cell maintenance by targeting cyclin A [Developmental Biology]

2017-05-08T11:57:48-07:00

Drosophila germ-line stem cells (GSCs) provide an excellent model to study the regulatory mechanisms of stem cells in vivo. Bag of marbles (bam) has been demonstrated to be necessary and sufficient to promote GSC and cystoblast differentiation. Despite extensive investigation of its regulation and genetic functions, the biochemical nature of...



Protein composition of the hepatitis A virus quasi-envelope [Microbiology]

2017-05-10T12:03:27-07:00

The Picornaviridae are a diverse family of RNA viruses including many pathogens of medical and veterinary importance. Classically considered “nonenveloped,” recent studies show that some picornaviruses, notably hepatitis A virus (HAV; genus Hepatovirus) and some members of the Enterovirus genus, are released from cells nonlytically in membranous vesicles. To better...



Streptococcus pneumoniae capsular polysaccharide is linked to peptidoglycan via a direct glycosidic bond to {beta}-D-N-acetylglucosamine [Microbiology]

2017-05-11T13:24:05-07:00

For many bacteria, including those important in pathogenesis, expression of a surface-localized capsular polysaccharide (CPS) can be critical for survival in host environments. In Gram-positive bacteria, CPS linkage is to either the cytoplasmic membrane or the cell wall. Despite the frequent occurrence and essentiality of these polymers, the exact nature...



Laboratory measurements of HDO/H2O isotopic fractionation during ice deposition in simulated cirrus clouds [Earth, Atmospheric, and Planetary Sciences]

2017-05-11T13:24:05-07:00

The stable isotopologues of water have been used in atmospheric and climate studies for over 50 years, because their strong temperature-dependent preferential condensation makes them useful diagnostics of the hydrological cycle. However, the degree of preferential condensation between vapor and ice has never been directly measured at temperatures below 233...



Probing the lithium-response pathway in hiPSCs implicates the phosphoregulatory set-point for a cytoskeletal modulator in bipolar pathogenesis [Medical Sciences]

2017-05-12T13:50:40-07:00

The molecular pathogenesis of bipolar disorder (BPD) is poorly understood. Using human-induced pluripotent stem cells (hiPSCs) to unravel such mechanisms in polygenic diseases is generally challenging. However, hiPSCs from BPD patients responsive to lithium offered unique opportunities to discern lithium's target and hence gain molecular insight into BPD. By profiling...



Fundamental trade-offs between information flow in single cells and cellular populations [Systems Biology]

2017-05-12T12:43:52-07:00

Signal transduction networks allow eukaryotic cells to make decisions based on information about intracellular state and the environment. Biochemical noise significantly diminishes the fidelity of signaling: networks examined to date seem to transmit less than 1 bit of information. It is unclear how networks that control critical cell-fate decisions (e.g.,...



Experimental evaluation of the generalized vibrational theory of G protein-coupled receptor activation [Biophysics and Computational Biology]

2017-05-12T12:43:53-07:00

Recently, an alternative theory concerning the method by which olfactory proteins are activated has garnered attention. This theory proposes that the activation of olfactory G protein-coupled receptors occurs by an inelastic electron tunneling mechanism that is mediated through the presence of an agonist with an appropriate vibrational state to accept...



Regulation of the sperm calcium channel CatSper by endogenous steroids and plant triterpenoids [Physiology]

2017-05-15T11:52:13-07:00

The calcium channel of sperm (CatSper) is essential for sperm hyperactivated motility and fertility. The steroid hormone progesterone activates CatSper of human sperm via binding to the serine hydrolase ABHD2. However, steroid specificity of ABHD2 has not been evaluated. Here, we explored whether steroid hormones to which human spermatozoa are...



Highly active catalyst derived from a 3D foam of Fe(PO3)2/Ni2P for extremely efficient water oxidation [Chemistry]

2017-05-15T11:52:13-07:00

Commercial hydrogen production by electrocatalytic water splitting will benefit from the realization of more efficient and less expensive catalysts compared with noble metal catalysts, especially for the oxygen evolution reaction, which requires a current density of 500 mA/cm2 at an overpotential below 300 mV with long-term stability. Here we report...



Essential information: Uncertainty and optimal control of Ebola outbreaks [Ecology]

2017-05-15T11:52:13-07:00

Early resolution of uncertainty during an epidemic outbreak can lead to rapid and efficient decision making, provided that the uncertainty affects prioritization of actions. The wide range in caseload projections for the 2014 Ebola outbreak caused great concern and debate about the utility of models. By coding and running 37...



Control of metastatic niche formation by targeting APBA3/Mint3 in inflammatory monocytes [Cell Biology]

2017-05-15T11:52:14-07:00

Cancer metastasis is intricately orchestrated by both cancer and normal cells, such as endothelial cells and macrophages. Monocytes/macrophages, which are often co-opted by cancer cells and promote tumor malignancy, acquire more than half of their energy from glycolysis even during normoxic conditions. This glycolytic activity is maintained during normoxia by...



Large-moment antiferromagnetic order in overdoped high-Tc superconductor 154SmFeAsO1-xDx [Physics]

2017-05-15T11:52:14-07:00

In iron-based superconductors, high critical temperature (Tc) superconductivity over 50 K has only been accomplished in electron-doped hREFeAsO (hRE is heavy rare earth (RE) element). Although hREFeAsO has the highest bulk Tc (58 K), progress in understanding its physical properties has been relatively slow due to difficulties in achieving high-concentration...



Thiophene antibacterials that allosterically stabilize DNA-cleavage complexes with DNA gyrase [Microbiology]

2017-05-15T11:52:14-07:00

A paucity of novel acting antibacterials is in development to treat the rising threat of antimicrobial resistance, particularly in Gram-negative hospital pathogens, which has led to renewed efforts in antibiotic drug discovery. Fluoroquinolones are broad-spectrum antibacterials that target DNA gyrase by stabilizing DNA-cleavage complexes, but their clinical utility has been...



Effective control of complex turbulent dynamical systems through statistical functionals [Applied Mathematics]

2017-05-15T11:52:14-07:00

Turbulent dynamical systems characterized by both a high-dimensional phase space and a large number of instabilities are ubiquitous among complex systems in science and engineering, including climate, material, and neural science. Control of these complex systems is a grand challenge, for example, in mitigating the effects of climate change or...



Direct observation of structure and dynamics during phase separation of an elastomeric protein [Biophysics and Computational Biology]

2017-05-15T11:52:15-07:00

Despite its growing importance in biology and in biomaterials development, liquid–liquid phase separation of proteins remains poorly understood. In particular, the molecular mechanisms underlying simple coacervation of proteins, such as the extracellular matrix protein elastin, have not been reported. Coacervation of the elastin monomer, tropoelastin, in response to heat and...



Development of visual category selectivity in ventral visual cortex does not require visual experience [Neuroscience]

2017-05-15T11:52:15-07:00

To what extent does functional brain organization rely on sensory input? Here, we show that for the penultimate visual-processing region, ventral-temporal cortex (VTC), visual experience is not the origin of its fundamental organizational property, category selectivity. In the fMRI study reported here, we presented 14 congenitally blind participants with face-,...



Exceptional and rapid accumulation of anthropogenic debris on one of the world’s most remote and pristine islands [Sustainability Science]

2017-05-15T11:52:15-07:00

In just over half a century plastic products have revolutionized human society and have infiltrated terrestrial and marine environments in every corner of the globe. The hazard plastic debris poses to biodiversity is well established, but mitigation and planning are often hampered by a lack of quantitative data on accumulation...



Nonpeptide orexin type-2 receptor agonist ameliorates narcolepsy-cataplexy symptoms in mouse models [Pharmacology]

2017-05-15T11:52:16-07:00

Narcolepsy-cataplexy is a debilitating disorder of sleep/wakefulness caused by a loss of orexin-producing neurons in the lateroposterior hypothalamus. Genetic or pharmacologic orexin replacement ameliorates symptoms in mouse models of narcolepsy-cataplexy. We have recently discovered a potent, nonpeptide OX2R-selective agonist, YNT-185. This study validates the pharmacological activity of this compound in...



Spatially restricted dental regeneration drives pufferfish beak development [Evolution]

2017-05-15T11:52:16-07:00

Vertebrate dentitions are extraordinarily diverse in both morphology and regenerative capacity. The teleost order Tetraodontiformes exhibits an exceptional array of novel dental morphologies, epitomized by constrained beak-like dentitions in several families, i.e., porcupinefishes, three-toothed pufferfishes, ocean sunfishes, and pufferfishes. Modification of tooth replacement within these groups leads to the progressive...



Involvement of a gut-retina axis in protection against dietary glycemia-induced age-related macular degeneration [Medical Sciences]

2017-05-15T11:52:16-07:00

Age-related macular degeneration (AMD) is the major cause of blindness in developed nations. AMD is characterized by retinal pigmented epithelial (RPE) cell dysfunction and loss of photoreceptor cells. Epidemiologic studies indicate important contributions of dietary patterns to the risk for AMD, but the mechanisms relating diet to disease remain unclear....



Identification of Cav2-PKC{beta} and Cav2-NOS1 complexes as entities for ultrafast electrochemical coupling [Biophysics and Computational Biology]

2017-05-15T11:52:16-07:00

Voltage-activated calcium (Cav) channels couple intracellular signaling pathways to membrane potential by providing Ca2+ ions as second messengers at sufficiently high concentrations to modulate effector proteins located in the intimate vicinity of those channels. Here we show that protein kinase Cβ (PKCβ) and brain nitric oxide synthase (NOS1), both identified...



Cholinergic shaping of neural correlations [Neuroscience]

2017-05-15T11:52:17-07:00

A primary function of the brain is to form representations of the sensory world. Its capacity to do so depends on the relationship between signal correlations, associated with neuronal receptive fields, and noise correlations, associated with neuronal response variability. It was recently shown that the behavioral relevance of sensory stimuli...



Dopaminergic modulation of basal ganglia output through coupled excitation-inhibition [Neuroscience]

2017-05-15T11:52:17-07:00

Learning and maintenance of skilled movements require exploration of motor space and selection of appropriate actions. Vocal learning and social context-dependent plasticity in songbirds depend on a basal ganglia circuit, which actively generates vocal variability. Dopamine in the basal ganglia reduces trial-to-trial neural variability when the bird engages in courtship...



Parallel memory traces are built after an experience containing aversive and appetitive components in the crab Neohelice [Neuroscience]

2017-05-15T11:52:17-07:00

The neurobiology of learning and memory has been mainly studied by focusing on pure aversive or appetitive experiences. Here, we challenged this approach considering that real-life stimuli come normally associated with competing aversive and appetitive consequences and that interaction between conflicting information must be intrinsic part of the memory processes....



OCD candidate gene SLC1A1/EAAT3 impacts basal ganglia-mediated activity and stereotypic behavior [Neuroscience]

2017-05-15T11:52:17-07:00

Obsessive-compulsive disorder (OCD) is a chronic, disabling condition with inadequate treatment options that leave most patients with substantial residual symptoms. Structural, neurochemical, and behavioral findings point to a significant role for basal ganglia circuits and for the glutamate system in OCD. Genetic linkage and association studies in OCD point to...



Arabidopsis glycosylphosphatidylinositol-anchored protein LLG1 associates with and modulates FLS2 to regulate innate immunity [Plant Biology]

2017-05-15T11:52:18-07:00

Plants detect and respond to pathogen invasion with membrane-localized pattern recognition receptors (PRRs), which recognize pathogen-associated molecular patterns (PAMPs) and activate downstream immune responses. Here we report that Arabidopsis thaliana LORELEI-LIKE GPI-ANCHORED PROTEIN 1 (LLG1), a coreceptor of the receptor-like kinase FERONIA, regulates PRR signaling. In a forward genetic screen...



Stem cell migration and mechanotransduction on linear stiffness gradient hydrogels [Cell Biology]

2017-05-15T11:52:18-07:00

The spatial presentation of mechanical information is a key parameter for cell behavior. We have developed a method of polymerization control in which the differential diffusion distance of unreacted cross-linker and monomer into a prepolymerized hydrogel sink results in a tunable stiffness gradient at the cell–matrix interface. This simple, low-cost,...



Long-read sequencing uncovers the adaptive topography of a carnivorous plant genome [Evolution]

2017-05-15T11:52:18-07:00

Utricularia gibba, the humped bladderwort, is a carnivorous plant that retains a tiny nuclear genome despite at least two rounds of whole genome duplication (WGD) since common ancestry with grapevine and other species. We used a third-generation genome assembly with several complete chromosomes to reconstruct the two most recent lineage-specific...



Linkage disequilibrium matches forensic genetic records to disjoint genomic marker sets [Statistics]

2017-05-15T11:52:19-07:00

Combining genotypes across datasets is central in facilitating advances in genetics. Data aggregation efforts often face the challenge of record matching—the identification of dataset entries that represent the same individual. We show that records can be matched across genotype datasets that have no shared markers based on linkage disequilibrium between...



Pulses of Ca2+ coordinate actin assembly and exocytosis for stepwise cell extension [Microbiology]

2017-05-15T11:52:19-07:00

Many eukaryotic cells grow by extending their cell periphery in pulses. The molecular mechanisms underlying this process are not yet fully understood. Here we present a comprehensive model of stepwise cell extension by using the unique tip growth system of filamentous fungi. Live-cell imaging analysis, including superresolution microscopy, revealed that...



Quantitative assessment of passive electrical properties of the cardiac T-tubular system by FRAP microscopy [Physiology]

2017-05-15T11:52:19-07:00

Well-coordinated activation of all cardiomyocytes must occur on every heartbeat. At the cell level, a complex network of sarcolemmal invaginations, called the transverse-axial tubular system (TATS), propagates membrane potential changes to the cell core, ensuring synchronous and uniform excitation–contraction coupling. Although myocardial conduction of excitation has been widely described, the...



Controllable load sharing for soft adhesive interfaces on three-dimensional surfaces [Engineering]

2017-05-15T11:52:20-07:00

For adhering to three-dimensional (3D) surfaces or objects, current adhesion systems are limited by a fundamental trade-off between 3D surface conformability and high adhesion strength. This limitation arises from the need for a soft, mechanically compliant interface, which enables conformability to nonflat and irregularly shaped surfaces but significantly reduces the...



Critical roles of DNA demethylation in the activation of ripening-induced genes and inhibition of ripening-repressed genes in tomato fruit [Plant Biology]

2017-05-15T11:52:20-07:00

DNA methylation is a conserved epigenetic mark important for genome integrity, development, and environmental responses in plants and mammals. Active DNA demethylation in plants is initiated by a family of 5-mC DNA glycosylases/lyases (i.e., DNA demethylases). Recent reports suggested a role of active DNA demethylation in fruit ripening in tomato....



In vivo photolabeling of tumor-infiltrating cells reveals highly regulated egress of T-cell subsets from tumors [Immunology and Inflammation]

2017-05-15T11:52:20-07:00

Immune therapy is rapidly gaining prominence in the clinic as a major weapon against cancer. Whereas much attention has been focused on the infiltration of tumors by immune cells, the subsequent fate of these infiltrates remains largely unexplored. We therefore established a photoconversion-based model that allowed us to label tumor-infiltrating...



Plate tectonic regulation of global marine animal diversity [Earth, Atmospheric, and Planetary Sciences]

2017-05-15T11:52:20-07:00

Valentine and Moores [Valentine JW, Moores EM (1970) Nature 228:657–659] hypothesized that plate tectonics regulates global biodiversity by changing the geographic arrangement of continental crust, but the data required to fully test the hypothesis were not available. Here, we use a global database of marine animal fossil occurrences and a...



Identification of XAF1-MT2A mutual antagonism as a molecular switch in cell-fate decisions under stressful conditions [Medical Sciences]

2017-05-15T11:52:21-07:00

XIAP-associated factor 1 (XAF1) is a tumor suppressor that is commonly inactivated in multiple human neoplasms. However, the molecular mechanism underlying its proapoptotic function remains largely undefined. Here, we report that XAF1 induction by heavy metals triggers an apoptotic switch of stress response by destabilizing metallothionein 2A (MT2A). XAF1 directly...



Embryonic transcription factor SOX9 drives breast cancer endocrine resistance [Medical Sciences]

2017-05-15T11:52:22-07:00

The estrogen receptor (ER) drives the growth of most luminal breast cancers and is the primary target of endocrine therapy. Although ER blockade with drugs such as tamoxifen is very effective, a major clinical limitation is the development of endocrine resistance especially in the setting of metastatic disease. Preclinical and...



Information socialtaxis and efficient collective behavior emerging in groups of information-seeking agents [Ecology]

2017-05-15T11:52:22-07:00

Individual behavior, in biology, economics, and computer science, is often described in terms of balancing exploration and exploitation. Foraging has been a canonical setting for studying reward seeking and information gathering, from bacteria to humans, mostly focusing on individual behavior. Inspired by the gradient-climbing nature of chemotaxis, the infotaxis algorithm...



RNA primer-primase complexes serve as the signal for polymerase recycling and Okazaki fragment initiation in T4 phage DNA replication [Biochemistry]

2017-05-15T11:52:11-07:00

The opposite strand polarity of duplex DNA necessitates that the leading strand is replicated continuously whereas the lagging strand is replicated in discrete segments known as Okazaki fragments. The lagging-strand polymerase sometimes recycles to begin the synthesis of a new Okazaki fragment before finishing the previous fragment, creating a gap...



Translation and folding of single proteins in real time [Biophysics and Computational Biology]

2017-05-15T11:52:12-07:00

Protein biosynthesis is inherently coupled to cotranslational protein folding. Folding of the nascent chain already occurs during synthesis and is mediated by spatial constraints imposed by the ribosomal exit tunnel as well as self-interactions. The polypeptide’s vectorial emergence from the ribosomal tunnel establishes the possible folding pathways leading to its...



Impact of International Monetary Fund programs on child health [Population Biology]

2017-05-15T11:52:12-07:00

Parental education is located at the center of global efforts to improve child health. In a developing-country context, the International Monetary Fund (IMF) plays a crucial role in determining how governments allocate scarce resources to education and public health interventions. Under reforms mandated by IMF structural adjustment programs, it may...



Investigation of hindwing folding in ladybird beetles by artificial elytron transplantation and microcomputed tomography [Engineering]

2017-05-15T11:52:12-07:00

Ladybird beetles are high-mobility insects and explore broad areas by switching between walking and flying. Their excellent wing transformation systems enabling this lifestyle are expected to provide large potential for engineering applications. However, the mechanism behind the folding of their hindwings remains unclear. The reason is that ladybird beetles close...



Emergent magnetism at transition-metal-nanocarbon interfaces [Applied Physical Sciences]

2017-05-15T11:52:12-07:00

Charge transfer at metallo–molecular interfaces may be used to design multifunctional hybrids with an emergent magnetization that may offer an eco-friendly and tunable alternative to conventional magnets and devices. Here, we investigate the origin of the magnetism arising at these interfaces by using different techniques to probe 3d and 5d...



Loss of the homologous recombination gene rad51 leads to Fanconi anemia-like symptoms in zebrafish [Genetics]

2017-05-16T08:29:54-07:00

RAD51 is an indispensable homologous recombination protein, necessary for strand invasion and crossing over. It has recently been designated as a Fanconi anemia (FA) gene, following the discovery of two patients carrying dominant-negative mutations. FA is a hereditary DNA-repair disorder characterized by various congenital abnormalities, progressive bone marrow failure, and...



Ubiquitin- and ATP-dependent unfoldase activity of P97/VCP•NPLOC4•UFD1L is enhanced by a mutation that causes multisystem proteinopathy [Biochemistry]

2017-05-16T08:29:54-07:00

p97 is a “segregase” that plays a key role in numerous ubiquitin (Ub)-dependent pathways such as ER-associated degradation. It has been hypothesized that p97 extracts proteins from membranes or macromolecular complexes to enable their proteasomal degradation; however, the complex nature of p97 substrates has made it difficult to directly observe...



Energetic cost of building a virus [Biophysics and Computational Biology]

2017-05-16T08:29:54-07:00

Viruses are incapable of autonomous energy production. Although many experimental studies make it clear that viruses are parasitic entities that hijack the molecular resources of the host, a detailed estimate for the energetic cost of viral synthesis is largely lacking. To quantify the energetic cost of viruses to their hosts,...



Increasing intracellular magnesium levels with the 31-amino acid MgtS protein [Microbiology]

2017-05-16T08:29:55-07:00

Synthesis of the 31-amino acid, inner membrane protein MgtS (formerly denoted YneM) is induced by very low Mg2+ in a PhoPQ-dependent manner in Escherichia coli. Here we report that MgtS acts to increase intracellular Mg2+ levels and maintain cell integrity upon Mg2+ depletion. Upon development of a functional tagged derivative...



Shear bands as manifestation of a criticality in yielding amorphous solids [Applied Physical Sciences]

2017-05-16T08:29:55-07:00

Amorphous solids increase their stress as a function of an applied strain until a mechanical yield point whereupon the stress cannot increase anymore, afterward exhibiting a steady state with a constant mean stress. In stress-controlled experiments, the system simply breaks when pushed beyond this mean stress. The ubiquity of this...



Looplessness in networks is linked to trophic coherence [Ecology]

2017-05-16T08:29:55-07:00

Many natural, complex systems are remarkably stable thanks to an absence of feedback acting on their elements. When described as networks these exhibit few or no cycles, and associated matrices have small leading eigenvalues. It has been suggested that this architecture can confer advantages to the system as a whole,...



Kinematics of the lever arm swing in myosin VI [Biophysics and Computational Biology]

2017-05-16T08:29:55-07:00

Myosin VI (MVI) is the only known member of the myosin superfamily that, upon dimerization, walks processively toward the pointed end of the actin filament. The leading head of the dimer directs the trailing head forward with a power stroke, a conformational change of the motor domain exaggerated by the...



The general form of Hamilton’s rule makes no predictions and cannot be tested empirically [Evolution]

2017-05-16T08:29:55-07:00

Hamilton’s rule asserts that a trait is favored by natural selection if the benefit to others, B, multiplied by relatedness, R, exceeds the cost to self, C. Specifically, Hamilton’s rule states that the change in average trait value in a population is proportional to BR−C. This rule is commonly believed...



High Arctic Holocene temperature record from the Agassiz ice cap and Greenland ice sheet evolution [Environmental Sciences]

2017-05-16T08:45:01-07:00

We present a revised and extended high Arctic air temperature reconstruction from a single proxy that spans the past ∼12,000 y (up to 2009 CE). Our reconstruction from the Agassiz ice cap (Ellesmere Island, Canada) indicates an earlier and warmer Holocene thermal maximum with early Holocene temperatures that are 4–5...



Reply to Padmanabhan and Dixit: Hepatitis C virus entry inhibitors for optimally boosting direct-acting antiviral-based treatments [Letters (Online Only)]

2017-05-16T09:03:39-07:00

We thank Padmanabhan and Dixit for their comments (1) on our paper (2). They pointed out that entry inhibitors might form potent partners for optimal drug combinations. They analyzed previously published data on 10 hepatitis C virus (HCV) entry inhibitors that are under clinical or preclinical development and found some...



Inhibitors of hepatitis C virus entry may be potent ingredients of optimal drug combinations [Letters (Online Only)]

2017-05-16T09:27:16-07:00

With the large number of drugs now approved for the treatment of chronic hepatitis C virus (HCV) infection and an even larger number under development, rational identification of effective drug combinations becomes necessary for better disease management and the judicious design of clinical trials. In PNAS, Koizumi et al. (1)...



Control of Hsp90 chaperone and its clients by N-terminal acetylation and the N-end rule pathway [Biochemistry]

2017-05-17T11:51:10-07:00

We found that the heat shock protein 90 (Hsp90) chaperone system of the yeast Saccharomyces cerevisiae is greatly impaired in naa10Δ cells, which lack the NatA Nα-terminal acetylase (Nt-acetylase) and therefore cannot N-terminally acetylate a majority of normally N-terminally acetylated proteins, including Hsp90 and most of its cochaperones. Chk1, a...



Astrocytic glycogen-derived lactate fuels the brain during exhaustive exercise to maintain endurance capacity [Neuroscience]

2017-05-17T11:51:10-07:00

Brain glycogen stored in astrocytes provides lactate as an energy source to neurons through monocarboxylate transporters (MCTs) to maintain neuronal functions such as hippocampus-regulated memory formation. Although prolonged exhaustive exercise decreases brain glycogen, the role of this decrease and lactate transport in the exercising brain remains less clear. Because muscle...



Low temperature nullifies the circadian clock in cyanobacteria through Hopf bifurcation [Biophysics and Computational Biology]

2017-05-17T11:51:10-07:00

Cold temperatures lead to nullification of circadian rhythms in many organisms. Two typical scenarios explain the disappearance of rhythmicity: the first is oscillation death, which is the transition from self-sustained oscillation to damped oscillation that occurs at a critical temperature. The second scenario is oscillation arrest, in which oscillation terminates...



Solar thermochemical splitting of water to generate hydrogen [Perspectives]

2017-05-18T11:58:25-07:00

Solar photochemical means of splitting water (artificial photosynthesis) to generate hydrogen is emerging as a viable process. The solar thermochemical route also promises to be an attractive means of achieving this objective. In this paper we present different types of thermochemical cycles that one can use for the purpose. These...



Retrospective analysis of natural products provides insights for future discovery trends [Applied Biological Sciences]

2017-05-01T12:09:24-07:00

Understanding of the capacity of the natural world to produce secondary metabolites is important to a broad range of fields, including drug discovery, ecology, biosynthesis, and chemical biology, among others. Both the absolute number and the rate of discovery of natural products have increased significantly in recent years. However, there...



Alterations in cellular metabolism triggered by URA7 or GLN3 inactivation cause imbalanced dNTP pools and increased mutagenesis [Genetics]

2017-04-17T11:49:13-07:00

Eukaryotic DNA replication fidelity relies on the concerted action of DNA polymerase nucleotide selectivity, proofreading activity, and DNA mismatch repair (MMR). Nucleotide selectivity and proofreading are affected by the balance and concentration of deoxyribonucleotide (dNTP) pools, which are strictly regulated by ribonucleotide reductase (RNR). Mutations preventing DNA polymerase proofreading activity...



Spread of Zika virus in the Americas [Biophysics and Computational Biology]

2017-04-25T07:55:40-07:00

We use a data-driven global stochastic epidemic model to analyze the spread of the Zika virus (ZIKV) in the Americas. The model has high spatial and temporal resolution and integrates real-world demographic, human mobility, socioeconomic, temperature, and vector density data. We estimate that the first introduction of ZIKV to Brazil...



Major contribution of the 3/6/7 class of TRPC channels to myocardial ischemia/reperfusion and cellular hypoxia/reoxygenation injuries [Cell Biology]

2017-05-19T13:14:09-07:00

The injury phase after myocardial infarcts occurs during reperfusion and is a consequence of calcium release from internal stores combined with calcium entry, leading to cell death by apoptopic and necrotic processes. The mechanism(s) by which calcium enters cells has(ve) not been identified. Here, we identify canonical transient receptor potential...



Selective regulation of Notch ligands during angiogenesis is mediated by vimentin [Cell Biology]

2017-05-22T11:50:35-07:00

Notch signaling is a key regulator of angiogenesis, in which sprouting is regulated by an equilibrium between inhibitory Dll4-Notch signaling and promoting Jagged-Notch signaling. Whereas Fringe proteins modify Notch receptors and strengthen their activation by Dll4 ligands, other mechanisms balancing Jagged and Dll4 signaling are yet to be described. The...



Female peer mentors early in college increase women’s positive academic experiences and retention in engineering [Psychological and Cognitive Sciences]

2017-05-22T11:50:35-07:00

Scientific and engineering innovation is vital for American competitiveness, quality of life, and national security. However, too few American students, especially women, pursue these fields. Although this problem has attracted enormous attention, rigorously tested interventions outside artificial laboratory settings are quite rare. To address this gap, we conducted a longitudinal...



Healthy offspring from freeze-dried mouse spermatozoa held on the International Space Station for 9 months [Agricultural Sciences]

2017-05-22T11:50:35-07:00

If humans ever start to live permanently in space, assisted reproductive technology using preserved spermatozoa will be important for producing offspring; however, radiation on the International Space Station (ISS) is more than 100 times stronger than that on Earth, and irradiation causes DNA damage in cells and gametes. Here we...



cGAS is essential for cellular senescence [Immunology and Inflammation]

2017-05-22T11:50:35-07:00

Cellular senescence is a natural barrier to tumorigenesis and it contributes to the antitumor effects of several therapies, including radiation and chemotherapeutic drugs. Senescence also plays an important role in aging, fibrosis, and tissue repair. The DNA damage response is a key event leading to senescence, which is characterized by...



Collective action and the evolution of social norm internalization [Anthropology]

2017-05-22T11:50:36-07:00

Human behavior is strongly affected by culturally transmitted norms and values. Certain norms are internalized (i.e., acting according to a norm becomes an end in itself rather than merely a tool in achieving certain goals or avoiding social sanctions). Humans’ capacity to internalize norms likely evolved in our ancestors to...



Changes in conformational equilibria regulate the activity of the Dcp2 decapping enzyme [Biophysics and Computational Biology]

2017-05-22T11:50:36-07:00

Crystal structures of enzymes are indispensable to understanding their mechanisms on a molecular level. It, however, remains challenging to determine which structures are adopted in solution, especially for dynamic complexes. Here, we study the bilobed decapping enzyme Dcp2 that removes the 5′ cap structure from eukaryotic mRNA and thereby efficiently...



Prediction of disease activity in models of multiple sclerosis by molecular magnetic resonance imaging of P-selectin [Neuroscience]

2017-05-22T11:50:36-07:00

New strategies for detecting disease activity in multiple sclerosis are being investigated to ameliorate diagnosis and follow-up of patients. Today, although magnetic resonance imaging (MRI) is widely used to diagnose and monitor multiple sclerosis, no imaging tools exist to predict the evolution of disease and the efficacy of therapeutic strategies....



Mechanism of H2S-mediated protection against oxidative stress in Escherichia coli [Biochemistry]

2017-05-22T11:50:36-07:00

Endogenous hydrogen sulfide (H2S) renders bacteria highly resistant to oxidative stress, but its mechanism remains poorly understood. Here, we report that 3-mercaptopyruvate sulfurtransferase (3MST) is the major source of endogenous H2S in Escherichia coli. Cellular resistance to H2O2 strongly depends on the activity of mstA, a gene that encodes 3MST....



Data-driven modeling reveals cell behaviors controlling self-organization during Myxococcus xanthus development [Developmental Biology]

2017-05-22T11:50:37-07:00

Collective cell movement is critical to the emergent properties of many multicellular systems, including microbial self-organization in biofilms, embryogenesis, wound healing, and cancer metastasis. However, even the best-studied systems lack a complete picture of how diverse physical and chemical cues act upon individual cells to ensure coordinated multicellular behavior. Known...



Bio-inspired self-healing structural color hydrogel [Applied Physical Sciences]

2017-05-22T11:50:37-07:00

Biologically inspired self-healing structural color hydrogels were developed by adding a glucose oxidase (GOX)- and catalase (CAT)-filled glutaraldehyde cross-linked BSA hydrogel into methacrylated gelatin (GelMA) inverse opal scaffolds. The composite hydrogel materials with the polymerized GelMA scaffold could maintain the stability of an inverse opal structure and its resultant structural...



Phosphorylated Presenilin 1 decreases {beta}-amyloid by facilitating autophagosome-lysosome fusion [Neuroscience]

2017-05-22T11:50:37-07:00

Presenilin 1 (PS1), the catalytic subunit of the γ-secretase complex, cleaves βCTF to produce Aβ. We have shown that PS1 regulates Aβ levels by a unique bifunctional mechanism. In addition to its known role as the catalytic subunit of the γ-secretase complex, selective phosphorylation of PS1 on Ser367 decreases Aβ...



Insect pathogenic fungus interacts with the gut microbiota to accelerate mosquito mortality [Agricultural Sciences]

2017-05-22T11:50:37-07:00

The insect gut microbiota plays crucial roles in modulating the interactions between the host and intestinal pathogens. Unlike viruses, bacteria, and parasites, which need to be ingested to cause disease, entomopathogenic fungi infect insects through the cuticle and proliferate in the hemolymph. However, interactions between the gut microbiota and entomopathogenic...



Blue fluorescent amino acid for biological spectroscopy and microscopy [Applied Biological Sciences]

2017-05-22T11:50:37-07:00

Many fluorescent proteins are currently available for biological spectroscopy and imaging measurements, allowing a wide range of biochemical and biophysical processes and interactions to be studied at various length scales. However, in applications where a small fluorescence reporter is required or desirable, the choice of fluorophores is rather limited. As...



Visualization and characterization of individual type III protein secretion machines in live bacteria [Microbiology]

2017-05-22T11:50:38-07:00

Type III protein secretion machines have evolved to deliver bacterially encoded effector proteins into eukaryotic cells. Although electron microscopy has provided a detailed view of these machines in isolation or fixed samples, little is known about their organization in live bacteria. Here we report the visualization and characterization of the...



Mental models accurately predict emotion transitions [Psychological and Cognitive Sciences]

2017-05-22T11:50:38-07:00

Successful social interactions depend on people’s ability to predict others’ future actions and emotions. People possess many mechanisms for perceiving others’ current emotional states, but how might they use this information to predict others’ future states? We hypothesized that people might capitalize on an overlooked aspect of affective experience: current...



Unique clade of alphaproteobacterial endosymbionts induces complete cytoplasmic incompatibility in the coconut beetle [Microbiology]

2017-05-22T11:50:38-07:00

Maternally inherited bacterial endosymbionts in arthropods manipulate host reproduction to increase the fitness of infected females. Cytoplasmic incompatibility (CI) is one such manipulation, in which uninfected females produce few or no offspring when they mate with infected males. To date, two bacterial endosymbionts, Wolbachia and Cardinium, have been reported as...



KEAP1-modifying small molecule reveals muted NRF2 signaling responses in neural stem cells from Huntington's disease patients [Neuroscience]

2017-05-22T11:50:38-07:00

The activity of the transcription factor nuclear factor-erythroid 2 p45-derived factor 2 (NRF2) is orchestrated and amplified through enhanced transcription of antioxidant and antiinflammatory target genes. The present study has characterized a triazole-containing inducer of NRF2 and elucidated the mechanism by which this molecule activates NRF2 signaling. In a highly...



B12-dependent photoresponsive protein hydrogels for controlled stem cell/protein release [Biochemistry]

2017-05-22T11:50:38-07:00

Thanks to the precise control over their structural and functional properties, genetically engineered protein-based hydrogels have emerged as a promising candidate for biomedical applications. Given the growing demand for creating stimuli-responsive “smart” hydrogels, here we show the synthesis of entirely protein-based photoresponsive hydrogels by covalently polymerizing the adenosylcobalamin (AdoB12)-dependent photoreceptor...



Engineering Cu surfaces for the electrocatalytic conversion of CO2: Controlling selectivity toward oxygenates and hydrocarbons [Chemistry]

2017-05-22T11:50:39-07:00

In this study we control the surface structure of Cu thin-film catalysts to probe the relationship between active sites and catalytic activity for the electroreduction of CO2 to fuels and chemicals. Here, we report physical vapor deposition of Cu thin films on large-format (∼6 cm2) single-crystal substrates, and confirm epitaxial...



Pyrite sulfur isotopes reveal glacial-interglacial environmental changes [Earth, Atmospheric, and Planetary Sciences]

2017-05-22T11:50:39-07:00

The sulfur biogeochemical cycle plays a key role in regulating Earth’s surface redox through diverse abiotic and biological reactions that have distinctive stable isotopic fractionations. As such, variations in the sulfur isotopic composition (δ34S) of sedimentary sulfate and sulfide phases over Earth history can be used to infer substantive changes...



Learned response sequences in cerebellar Purkinje cells [Neuroscience]

2017-05-22T11:50:39-07:00

Associative learning in the cerebellum has previously focused on single movements. In eyeblink conditioning, for instance, a subject learns to blink at the right time in response to a conditional stimulus (CS), such as a tone that is repeatedly followed by an unconditional corneal stimulus (US). During conditioning, the CS...



CCR8+FOXp3+ Treg cells as master drivers of immune regulation [Immunology and Inflammation]

2017-05-22T11:50:39-07:00

The current study identifies CCR8+ regulatory T cells (Treg cells) as drivers of immunosuppression. We show that in human peripheral blood cells, more than 30% of Treg up-regulate CCR8 following activation in the presence of CCL1. This interaction induces STAT3-dependent up-regulation of FOXp3, CD39, IL-10, and granzyme B, resulting in...



Correction for Verhille et al., Structure and mechanics of aegagropilae fiber network [Corrections]

2017-05-22T11:50:39-07:00

APPLIED PHYSICAL SCIENCES Correction for “Structure and mechanics of aegagropilae fiber network,” by Gautier Verhille, Sébastien Moulinet, Nicolas Vandenberghe, Mokhtar Adda-Bedia, and Patrice Le Gal, which appeared in issue 18, May 2, 2017, of Proc Natl Acad Sci USA (114:4607–4612; first published April 17, 2017; 10.1073/pnas.1620688114). The authors note that...



Interplay of catalysis, fidelity, threading, and processivity in the exo- and endonucleolytic reactions of human exonuclease I [Biochemistry]

2017-05-22T11:50:40-07:00

Human exonuclease 1 (hExo1) is a member of the RAD2/XPG structure-specific 5′-nuclease superfamily. Its dominant, processive 5′–3′ exonuclease and secondary 5′-flap endonuclease activities participate in various DNA repair, recombination, and replication processes. A single active site processes both recessed ends and 5′-flap substrates. By initiating enzyme reactions in crystals, we...



Mechanosensing of shear by Pseudomonas aeruginosa leads to increased levels of the cyclic-di-GMP signal initiating biofilm development [Microbiology]

2017-05-22T11:50:40-07:00

Biofilms are communities of sessile microbes that are phenotypically distinct from their genetically identical, free-swimming counterparts. Biofilms initiate when bacteria attach to a solid surface. Attachment triggers intracellular signaling to change gene expression from the planktonic to the biofilm phenotype. For Pseudomonas aeruginosa, it has long been known that intracellular...



Changes in perceptual sensitivity related to spatial cues depends on subcortical activity [Neuroscience]

2017-05-22T11:50:40-07:00

Spatial cues allow animals to selectively attend to relevant visual stimuli while ignoring distracters. This process depends on a distributed neuronal network, and an important current challenge is to understand the functional contributions made by individual brain regions within this network and how these contributions interact. Recent findings point to...



Solitary bees reduce investment in communication compared with their social relatives [Evolution]

2017-05-22T11:50:40-07:00

Social animals must communicate to define group membership and coordinate social organization. For social insects, communication is predominantly mediated through chemical signals, and as social complexity increases, so does the requirement for a greater diversity of signals. This relationship is particularly true for advanced eusocial insects, including ants, bees, and...