This Week in Science

This Week in Science

Science  24 Feb 2017:
Vol. 355, Issue 6327, pp. 808
  1. Neuroscience

    How will this molecule smell?

    1. Peter Stern

    An algorithm successfully predicts how an unknown molecule will smell.

    CREDITS (FROM TOP): BLEICHERT ET AL.; CREDIT: IMAGE SOURCE/ALAMY STOCK PHOTO

    We still do not understand what a given substance will smell like. Keller et al. launched an international crowd-sourced competition in which many teams tried to solve how the smell of a molecule will be perceived by humans. The teams were given access to a database of responses from subjects who had sniffed a large number of molecules and been asked to rate each smell across a range of different qualities. The teams were also given a comprehensive list of the physical and chemical features of the molecules smelled. The teams produced algorithms to predict the correspondence between the quality of each smell and a given molecule. The best models that emerged from this challenge could accurately predict how a new molecule would smell.

    Science, this issue p. 820

  2. Microbiome

    Bacterial battles on your skin

    1. Lindsey Pujanandez

    Normal human skin is colonized by a variety of normally harmless bacteria. However, one such bacterium, Staphylococcus aureus, can aggravate symptoms of atopic dermatitis. Nakatsuji et al. report that other strains of Staphylococcus residing on the skin of healthy individuals produce an antimicrobial peptide that can inhibit S. aureus growth. Colonization of pigskin or mouse skin with these protective commensals reduced S. aureus replication. Furthermore, autologous bacterial transplant in a small number of atopic dermatitis patients drastically reduced S. aureus skin burden. This commensal skin transplant has already been approved by the U.S. Food and Drug Administration, and a clinical trial is under way.

    Sci. Transl. Med. 9, eaah4680 (2017).

  3. Cognition

    Very clever bees use tools

    1. Sacha Vignieri

    One hallmark of cognitive complexity is the ability to manipulate objects with a specific goal in mind. Such “tool use” at one time was ascribed to humans alone, but then to primates, next to marine mammals, and later to birds. Now we recognize that many species have the capacity to envision how a particular object might be used to achieve an end. Loukola et al. extend this insight to invertebrates. Bumblebees were trained to see that a ball could be used to produce a reward. These bees then spontaneously rolled the ball when given the chance.

    Science, this issue p. 833

  4. Vascular Disease

    Faulty blood cells and heart disease

    1. Paula A. Kiberstis

    Recent studies have shown that elderly people's blood cells often harbor mutations in genes encoding certain epigenetic regulators. These mutations can lead to clonal expansion of the mutant blood cells, which increases the risk of blood cancers and cardiovascular disease. Fuster et al. generated a mouse model to investigate how one of these genes, Tet2, affects atherosclerosis development (see the Perspective by Zhu et al.). They found that the disease progressed more rapidly in mice transplanted with Tet2-deficient bone marrow cells. This was due to increased secretion of interleukin-1β by Tet2-deficient macrophages in a process that depended on the action of inflammasomes.

    Science, this issue p. 842; see also p. 798

  5. Extreme Astrophysics

    Spinning up an extragalactic neutron star

    1. Keith T. Smith

    Ultraluminous x-ray sources (ULXs) are strange objects in other galaxies that cannot be explained by conventional accretion onto stellar-mass objects. This has led to exotic interpretations, such as the long-sought intermediate-mass black holes. Israel et al. observed a ULX in the nearby galaxy NGC 5907 and found that it is instead a neutron star. The spinning neutron star is accreting material so fast that its spin period is quickly accelerating. The only way that it can consume enough material to explain these properties is if it has a strong multipolar magnetic field.

    Science, this issue p. 817

  6. Protein Design

    Shining a light on cell signaling

    1. Valda Vinson

    Protein kinases are proteins that are used to transmit signals within cells. Zhou et al. engineered diverse kinases so that they could be switched on and off with visible light. They modified the fluorescent protein Dronpa so that instead of being tetrameric, it dimerized in violet light and dissociated in cyan light, and they fused two copies to representatives from different families of kinases. The engineered kinases could be photo-switched with spatial and temporal precision and were successfully used to study a variety of signaling pathways.

    Science, this issue p. 836

  7. Polymers

    How to make opposites compatible

    1. Marc S. Lavine

    A new processing approach helps mixed plastics recycling.

    PHOTO: BLACKOUT CONCEPTS/ALAMY STOCK PHOTO

    Polyethylene (PE) and isotactic polypropylene (iPP) are the two most widely used commodity plastics and thus make up a large fraction of the waste stream. However, the two plastics will not mix together, which limits options for dealing with mixed waste and decreases the value of recycled products. Eagan et al. report the synthesis of multiblock copolymers of iPP and PE by using a selective polymer initiator (see the Perspective by Creton). The high-molecular-weight blocks could be used to reinforce the interface between iPP and PE and allow blending of the two polymers.

    Science, this issue p. 814; see also p. 797

  8. Inflammation

    How red berries reduce inflammation

    1. John F. Foley

    Members of the interleukin-17 (IL-17) family of proinflammatory cytokines are important in the immune response to infections. However, too much IL-17 signaling is associated with autoimmune inflammatory diseases, such as asthma, psoriasis, and rheumatoid arthritis. Liu et al. performed small-molecule screening to look for compounds that could bind to the IL-17 receptor. They found that cyanidin, a flavonoid found in red berries and other fruits, bound to the IL-17 receptor and blocked the binding of IL-17A. In several mouse models of inflammatory disease, cyanidin alleviated the inflammation induced by IL-17A–producing T cells.

    Sci. Signal. 10, eaaf8823 (2017).

  9. DNA Replication

    Diverse molecular choreography of replication

    1. Guy Riddihough,
    2. Caroline Ash

    Accurate duplication and transmission of genetic information to the next generation requires complex molecular assemblies. Bleichert et al. review replication initiation across the three domains of life, with a focus on origin selection and helicase loading. These processes identify potential origins of replication and prepare them for subsequent bidirectional replication initiation. There are key similarities and multiple differences in replication mechanisms between eukaryotes, prokaryotes, and archaea and many outstanding questions to be answered.

    Science, this issue p. eaah6317

  10. Proteomics

    How proteomes take the heat

    1. Valda Vinson

    Living organisms are very sensitive to temperature, and much of this is attributed to its effect on the structure and function of proteins. Leuenberger et al. explored thermostability on a proteome-wide scale in bacteria, yeast, and human cells by using a combination of limited proteolysis and mass spectrometry (see the Perspective by Vogel). Their results suggest that temperature-induced cell death is caused by the loss of a subset of proteins with key functions. The study also provides insight into the molecular and evolutionary bases of protein and proteome stability.

    Science, this issue p. eaai7825; see also p. 794

  11. DNA Charge Transport

    DNA charged with regulating replication

    1. Guy Riddihough,
    2. Jake Yeston

    DNA can transport electrical charge over long distances and has the potential to act as a signaling system. The iron-sulfur complex [4Fe4S] found in some proteins is known to be involved in redox reactions. The eukaryotic DNA primase is involved in DNA replication and contains a [4Fe4S] cluster that is required for its RNA primer synthesis activity. O'Brien et al. show that the [4Fe4S] cluster in DNA primase can regulate the protein's DNA binding activity through DNA-mediated charge transfer. This in turn plays a role in primer initiation and length determination.

    Science, this issue p. eaag1789

  12. Antibiotic Resistance

    Resistance on a background of tolerance

    1. Caroline Ash

    Bacteria survive antibiotic exposure either because they are quiescent when antibiotics are around in the highest concentrations (i.e., tolerance) or because they acquire active biochemical resistance mechanisms (i.e., resistance). Both tolerance and resistance involve the acquisition of mutations from the wild type. Levin-Reisman et al. used in vitro evolution experiments to show that populations of bacteria that become genetically resistant to the antibiotic ampicillin most quickly do so on a background of tolerance mutations (see the Perspective by Lewis and Shan). Because the probability of a tolerant organism surviving is higher, it has a greater chance of subsequently acquiring resistance mutations. Tolerance is often overlooked in the clinic but should in future be screened for and targeted more precisely to reduce the rates of acquired resistance.

    Science, this issue p. 826; see also p. 796

  13. Toxic Amyloids

    What's in a fold?

    1. Stella M. Hurtley

    Bacterially secreted peptides known as PSMs (phenol-soluble modulins) stimulate inflammatory responses, lyse human cells, and contribute to biofilm structuring. PSMα3 is a virulent 22-residue amyloid peptide secreted by Staphylococcus aureus. Tayeb-Fligelman et al. present a high-resolution structure encompassing the full length of the amyloid's sequence. This structure reveals an unexpected departure from the common amyloid cross-β folded architecture. Instead, PSMα3 forms amphipathic α-helices that are folded to stack perpendicular to the fibril axis into sheets. This unusual cross-α structure was important for fibril toxicity.

    Science, this issue p. 831

  14. Paleontology

    How dinosaurs took to the air

    1. Julia Fahrenkamp-Uppenbrink

    Birds use their wings for powered flight, but, as Brusatte explains in a Perspective, this does not mean that wings evolved for this purpose. Early winged dinosaurs were not capable of flight. Later dinosaurs had a range of wing types that likely enabled different capabilities, from gliding to incipient flapping. Only much later did the predecessors of birds evolve the right body size, wing span, and anatomy to enable powered flight. Biomechanical studies are crucial for exploring which winged dinosaurs could move in the air and how they did so.

    Science, this issue p. 792

  15. Immunogenomics

    Defining the tree rings of T cells

    1. Anand Balasubramani

    T cell function declines with age. What does T cell aging look like at the molecular level? To understand the transcriptional programs that regulate T cell differentiation and aging, Moskowitz et al. generated genome-wide maps of chromatin accessibility in CD8+ T cells from young and elderly individuals. In naive CD8+ T cells in the elderly, promoters that recruit nuclear respiratory factor 1 (NRF1), which controls expression of mitochondrial proteins, were less accessible. Thus, loss of NRF1 binding could contribute to lower metabolic activity in aged T cells. The transcriptional circuits uncovered by this study set the stage for designing approaches to modulate T cell function in the elderly.

    Sci. Immunol. 2, eaag0192 (2017).