This Week in Science

Science  19 Jun 2015:
Vol. 348, Issue 6241, pp. 1327
  1. Protein Design

    Designing proteins to self-assemble

    1. Valda Vinson

    Computational design of programmable protein lattices

    IMAGE: VIKRAM K. MULLIGAN

    DNA has been used as a nano building material since the 1980s. Protein nanostructures have the potential to give greater geometric control and shape variability. Gonen et al. describe the computational design of proteins that self-assemble into two-dimensional arrays. These programmable protein lattices should enable new approaches in biomolecular structure determination and molecular sensing.

    Science, this issue p. 1365

  2. Induced Seismicity

    Making quakes depends on injection rates

    1. Brent Grocholski

    Wastewater injection wells induce earthquakes that garner much attention, especially in tectonically inactive regions. Weingarten et al. combined information from public injection-well databases from the eastern and central United States with the best earthquake catalog available over the past 30 years. The rate of fluid injection into a well appeared to be the most likely decisive triggering factor in regions prone to induced earthquakes. Along these lines, Walsh III and Zoback found a clear correlation between areas in Oklahoma where waste saltwater is being injected on a large scale and areas experiencing increased earthquake activity.

    Science, this issue p. 1336; Sci. Adv. 10.1126/sciadv.1500195 (2015).

  3. Cancer

    Telomerase stabilized by a sphingolipid

    1. Leslie K. Ferrarelli

    In normal adult cells, the structures at the ends of chromosomes, called telomeres, becomes progressively shorter with each replication cycle. When telomeres get too short or damaged, the cell stops dividing and becomes senescent. The enzyme telomerase maintains the integrity of telomeres, and phosphorylation stabilizes the catalytic subunit (called TERT) of this enzyme. In both normal fibroblasts and lung cancer cells, Selvam et al. found that binding of the phospholipid S1P to TERT prevented the degradation of TERT. Disrupting the interaction between S1P and TERT impaired telomere maintenance and promoted senescence in cultured cells and decreased the growth of lung cancer cell xenografts in mice.

    Sci. Signal. 8, ra58 (2015).

  4. Batteries

    Watching defects during battery cycling

    1. Marc S. Lavine

    Dislocations affect the mechanical properties of a material. Ulvestad et al. studied the influence of dislocations on a nanoparticle undergoing charge and discharge cycles in a lithium ion battery. The defects influenced the way the material expanded and contracted during cycling. In the future, it may be possible to tune the properties of a material through controlled defect engineering.

    Science, this issue p. 1344

  5. Cometary Nuclei

    Collisions give comets their shape

    1. Nicholas S. Wigginton

    Simulated comet shape

    IMAGE: JUTZI ET AL.

    The shape and structure of comets are relicts of collision processes from long ago. Despite recent and ongoing spacecraft missions that offer direct measurements of cometary nuclei, it is difficult to test what is important in comet shaping. Jutzi and Asphaug ran ∼100 three-dimensional collision simulations across a wide range of target and impactor masses and trajectories. Slow and less violent collisions produced the layering and bi-lobed shapes of actual comets.

    Science, this issue p. 1355

  6. Group Decisions

    Baboons follow the pack, not the leader

    1. Sacha Vignieri

    How do groups of animals, including humans, make decisions that affect the entire group? Evidence collected from schooling animals suggests that the process is somewhat democratic, with nearest neighbors and the majority shaping overall collective behavior. In animals with hierarchical social structures such as primates or wolves, however, such democracy may be complicated by dominance. Strandburg-Peshkin et al. monitored all the individuals within a baboon troop continuously over the course of their daily activities. Even within this highly socially structured species, movement decisions emerged via a shared process. Thus, democracy may be an inherent trait of collective behavior.

    Science, this issue p. 1358

  7. Endocytosis

    Bend me, shape me: Clathrin in action

    1. Stella M. Hurtley

    Endocytic clathrin-coated pits were among the first cellular structures described by electron microscopy over five decades ago. Despite this, the question remains: Does clathrin bind to the membrane as a flat lattice and then bend during coated pit invagination, or does clathrin assemble with a defined curvature as membranes invaginate? Avinoam et al. applied two state-of-the-art imaging approaches to resolve this conflict. They suggest that clathrin assembles into a defined flat lattice early in endocytosis, which predetermines the size of the vesicle. The assembled clathrin coat then rearranges through dynamic exchange of clathrin with the cytosolic pool to wrap around the forming vesicle.

    Science, this issue p. 1369

  8. Drug Development

    A degrading game plan for cancer therapy

    1. Paula A. Kiberstis

    Certain classes of proteins that contribute to cancer development are challenging to target therapeutically. Winter et al. devised a chemical strategy that, in principle, permits the selective degradation of any protein of interest. The strategy involves chemically attaching a ligand known to bind the desired protein to another molecule that hijacks an enzyme whose function is to direct proteins to the cell's protein degradation machinery. In a proof-of-concept study, they demonstrated selective degradation of a transcriptional coactivator called bromodomain-containing protein 4 and delayed the progression of leukemia in mice.

    Science, this issue p. 1376

  9. Membrane Filtration

    Composite membranes for filtering solvents

    1. Marc S. Lavine

    Much research has focused on finding membranes that can purify water or extract waste carbon dioxide. However, there is also a need for the removal of small molecules from organic liquids. Many existing processes are energy-intensive and can require large quantities of solvents. Karan et al. grew confined polymer layers on a patterned sacrificial support to give rippled thin films that were then placed on ceramic membranes (see the Perspective by Freger). The composite membrane showed high flux for organic solvents and good stability and was able to separate out small molecules with high efficiency.

    Science, this issue p. 1347; see also p. 1317

  10. Ocean Circulation

    On the success (or not) of climate models

    1. H. Jesse Smith

    Atlantic Meridional Overturning Circulation (AMOC) transports huge amounts of heat from low to high latitudes and has a major influence on climate. Climate models have predicted that global warming will cause the AMOC to slow, but concrete evidence of such a slowdown has been scarce. Srokosz and Bryden review a decade of observations of the AMOC that reveal an unexpected amount of variability over time scales from seasonal to decadal, as well as a general weakening over this time.

    Science, this issue p. 10.1126/science.1255575

  11. Polaron Dynamics

    Photoinduction of long-lived polarons

    1. Phil Szuromi

    Photosynthetic complexes and organic photovoltaics can rapidly create separated charges upon photoexcitation. However, unproductive charge recombination often occurs in the human-made system. This is in part because the charge acceptor and donor structures are much larger. Huber et al. created aqueous micelles that pair conjugated polyelectrolyte charge donors with fullerene acceptors at a much smaller interface. They observed the photoinduced formation of polarons—stable pairs of separated charges—with lifetimes of several days.

    Science, this issue p. 1340

  12. Vaccines

    The right combination for protection

    1. Kristen L. Mueller

    Despite its prevalence, no vaccine exists to protect against infection with the sexually transmitted bacterium Chlamydia trachomatis. Stary et al. now report on one potential vaccine candidate (see the Perspective by Brunham). Vaccinating with an ultraviolet light-inactivated C. trachomatis linked to adjuvant-containing charged nanoparticles protected female conventional and humanized mice against C. trachomatis infection. The vaccine conferred protection only when delivered through mucosal routes. Protection relied on targeting the bacteria to a particular population of immunogenic dendritic cells and inducing memory T cells that resided in the female genital tract.

    Science, this issue 10.1126/science.aaa8205; see also p. 1322

  13. Water Conservation

    How to use less water during drought

    1. Julia Fahrenkamp-Uppenbrink

    Urban populations require a lot of water, which is often sourced from the surrounding countryside. Water conservation strategies implemented during droughts—such as the ongoing drought in California—include watering restrictions and tiered pricing. How effective are these water conservation strategies? In a Perspective, Hogue and Pincetl highlight recent studies that have used highly resolved data, such as those from satellites or water meters, to address this question. Together with advanced data analysis tools and models, these data can help to determine the best local strategies for water conservation.

    Science, this issue p. 1319

  14. Neurodevelopment

    From blastula to neural crest, do not pass go

    1. Pamela J. Hines

    During vertebrate development, neural crest cells give rise to an unusual diversity of cells, including pigment cells, neurons, and cartilage. Traditionally, neural crest cells have been considered a derivative of neural ectoderm. Buitrago-Delgado et al. now show that neural crest cells have components of the molecular programs characteristic of blastula cells from earlier in development (see the Perspective by Hoppler and Wheeler). Blastula cells have the broad range of developmental potentials necessary to build the embryo. Neural crest cells may thus reflect persistence of the developmental programs characteristic of early development rather than re-specification of developmental programs after differentiation into neurectoderm.

    Science, this issue p. 1332; see also p. 1316

  15. Brain Processing

    Signal flow during sensorimotor choices

    1. Peter Stern

    Little is known about the flow of task signals across the brain. Siegel et al. simultaneously recorded from multiple units in the sensory, parietal, prefrontal, and motor cortex while monkeys were cued to perform one among two possible simple tasks. The proportion of neurons coding for stimuli, cues, tasks, and choices, and their response latency, varied across regions. Parietal and prefrontal brain regions encoded task information and choices with the same latency. Interestingly, all brain areas encoded all types of information. However, they differed functionally according to the proportions of neurons and their response latency.

    Science, this issue p. 1352

  16. Signal Transduction

    How a receptor transmits a signal

    1. Valda Vinson

    G protein–coupled receptors (GPCRs) transmit diverse external signals into the cell. When activated by an outside stimulus, they bind to a G protein inside the cell and accelerate exchange of a bound guanosine diphosphate (GDP) nucleotide for guanosine triphosphate, which initiates intercellular signaling. Dror et al. used atomic-level molecular dynamics simulations to show how GPCRs enhance GDP release. The G protein is dynamic and frequently adopts a conformation that exposes GDP even without the receptor bound. GPCR binding to this conformation favors an additional structural rearrangement that favors GDP release. The authors confirmed these predictions experimentally using double electron-electron resonance spectroscopy.

    Science, this issue p. 1361

  17. Transcription

    Multifunctional pioneers

    1. Beverly A. Purnell

    Proteins surround cellular DNA to silence gene expression. Early in development, proteins such as pioneer transcription factors facilitate the opening of this silenced chromatin structure. Hsu et al. describe an additional role for the PHA-4 pioneer transcription factor in nematode worms. PHA-4 recruited RNA polymerase II to target promoters before transcriptional onset, and this activity preceded its chromatin-opening duty. The multifunctional role identified for PHA-4 may be shared by other pioneer factors.

    Science, this issue p. 1372

  18. Conservation

    When is predator control acceptable?

    1. Julia Fahrenkamp-Uppenbrink

    Predators such as wolves were long seen as a problem to be controlled or even eliminated. Today, their value is more widely appreciated, but predators are still widely killed to bolster populations of threatened prey species or to protect livestock. In a Perspective, Woodroffe and Redpath argue that such predator control efforts are not always beneficial for prey species and often have unwelcome effects. Predator pressures on prey are often a result of human actions, such as habitat fragmentation, making prey species dependent on predator control unless their habitats are restored. Passions often run high on both sides of the predator control debate, and management efforts may not be effective unless they are also socially acceptable.

    Science, this issue p. 1312

  19. Cell Biology

    Sealing the envelope

    1. Lisa D. Chong

    During animal cell division, the nuclear envelope breaks down, allowing a mitotic spindle to organize duplicated chromosomes for separation into future daughter cells. How the envelope reforms around the chromatin has been a mystery. In a Perspective, Sundquist and Ullman describe how a cellular mechanism involved in a variety of membrane fission events also seals the nuclear envelope. The endosomal sorting complex required for transport (ESCRT) machinery assembles at the growing nuclear envelope and recruits other proteins. These proteins release chromatin from the mitotic spindle and close the membrane, readying the two daughter cells for separation.

    Science, this issue p. 1314

  20. Autoimmunity

    AIREing out autoimmunity

    1. Angela Colmone

    Because of mutations in the AIRE gene, patients with autoimmune polyendocrine syndrome type 1 (APS1) suffer dysfunction in multiple endocrine glands and are often infertile. Female infertility can be explained by autoimmune ovarian failure, but the causes of male infertility are unclear. Now Landegren et al. report that the prostatic secretory molecule tranglutaminase 4 (TGM4) is a male-specific autoantigen in APS1 patients that could contribute to subfertility. Autoantibodies to TGM4 appeared in APS1 patients beginning at puberty, and similar antibodies lead to destructive prostatitis in AIRE-deficient mice. Together, these data may explain the infertility observed in male APS1 patients.

    Sci. Transl. Med. 7, 292ra101 (2015).