Editors' Choice

Science  06 Oct 2017:
Vol. 358, Issue 6359, pp. 77
  1. Cancer

    Initiating lung cancer

    1. Gemma Alderton

    Cigarette smoke-induced epigenetic changes sensitize cells for mutation.

    Cigarette smoke contributes to epigenetic and genetic changes in lung cancer. But whether and how these alterations interact in lung cancer initiation has remained unclear. Vaz et al. showed that in immortalized lung epithelial cells, exposure to cigarette smoke condensate progressively altered the binding of chromatin-modifying enzymes to DNA and induced changes in DNA methylation in the absence of DNA mutations. Such epigenetically altered cells exhibited a stem cell-like chromatin state that sensitized them to later acquire oncogenic mutations and become lung cancer cells. Modeling cancer initiation is extremely difficult, but this is an important process to understand if we hope to find effective strategies to prevent cancer initiation and/or progression.

    Cancer Cell 32, 360 (2017).

  2. Gene Regulation

    Regulation through clustering

    1. Beverly A. Purnell

    Transcription factors convey information from the environment to influence gene regulation. These proteins bind promoter sequences for gene repression or activation, but the mechanism by which they find their target sequence is unclear. Wollman et al. examined gene regulation by the Mig1 repressor and the Msn2 activator. The Mig1 repressor is a zinc-finger DNA-binding protein that localizes to the nucleus when the yeast Saccharomyces cerevisiae is exposed to glucose. Using single-molecule fluorescent microscopy to track localization, the authors found that six to nine transcription factor molecules form clusters that move from the cytoplasm to the nucleus. The clusters may be stabilized in live cells by the properties of the cytoplasmic colloid. Clustered transcription factors seem to reduce promoter search time and permit more efficient gene regulation.

    eLife 10.7554/eLife.27451.001 (2017).

  3. Behavior

    Smothering seeing-eye training

    1. Caroline Ash

    Less involved mothers produce more successful guide dogs.

    PHOTO: CYCLONPHOTO/ISTOCK

    Guide dogs are valued for their ability to follow complex instructions and for resisting impulsive behaviors—admirable human traits, too. Guide dogs undergo controlled rearing and training programs and thus offer an opportunity for investigating the development of adult temperament. Bray et al. modeled how maternal behavior predicted the performance of pups. Vigilant, interactive mothers tended to rear pups that barked readily and were more aggressive—fine for a police dog. But for a guide dog, calmness, obedience, and concentration are needed. Puppies with less involved mothers—for instance, who stand up while suckling—are more likely to succeed on these scores. Too much neglect is stressful and a bad thing, but smothering leads to individuals who lack the experience of learning to deal with stress and solving problems.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1704303114 (2017).

  4. Biochemistry

    How does nitrogenase spring its trap?

    1. Jake Yeston

    It's a bit of a chemical mystery why, after eons of evolution to optimize efficiency, nitrogenase enzymes still make hydrogen as a by-product when they make ammonia. Recent work suggests that this step is key to binding the nitrogen molecule in the active site. Khadka et al. attached the molybdenum-iron protein of nitrogenase to an electrode to isolate the kinetics of hydrogen production. By measuring deuterium isotope effects and performing accompanying density functional theory calculations, they established that the rate-limiting step involves formation of one hydrogen molecule by proton transfer from sulfur to a bridging iron hydride.

    J. Am. Chem. Soc. 10.1021/jacs.7b07311 (2017).

  5. Physics

    An atomic ring around the rosie

    1. Jelena Stajic

    Although quantum computers are expected to be vastly better at certain tasks than classical ones, they must also simultaneously perform sophisticated error control and correction. Using topologically protected states could reduce this baggage, but finding a viable physical implementation is tricky. Dai et al. engineered an interacting system of bosonic atoms on a square plaquette that could serve as a basis for creating topological states. The researchers had to carefully control the exchange interactions between the atoms to bring out the so-called ring exchange that involved all four atoms on a plaquette. It is expected that further technological progress could lead to scaling up this system into a network of coupled plaquettes with more dominant ring-exchange interactions.

    Nat. Phys. 10.1038/NPHYS4243 (2017).

  6. Physiology

    Gut bacteria may tell human cells what to do

    1. L. Bryan Ray

    New studies are providing glimpses of the language through which bacteria in the human gut communicate with us. Cohen et al. analyzed the DNA from the human microbiome for members of the N-acyl synthase family of proteins—enzymes that catalyze synthesis of molecules that might serve as ligands for human heterotrimeric G protein-coupled receptors (GPCRs). More than 140 such genes were detected, and they produced molecules that bound and efficiently activated human GPCRs. Transfer of bacteria engineered to express such ligands into mice altered glucose metabolism to a similar extent as did a drug used to treat diabetes. Thus, bacteria, which communicate with each other through small excreted molecules, may communicate with their host in a similar manner—thereby offering opportunities for therapeutic intervention.

    Nature 10.1038/nature23874 (2017).

  7. Stellar Astrophysics

    An expanding shell around an evolved star

    1. Keith T. Smith

    When intermediate-mass stars approach the ends of their lifetimes, they begin to shed their outer layers. Bursts of nuclear reactions in the stellar core lead to thermal pulses, temporarily increasing the mass-loss rate for several centuries. Kerschbaum et al. have mapped the carbon monoxide gas ejected by the nearby evolved star U Antliae. The gas forms an almost perfectly symmetric expanding shell around the star. By measuring the velocity of the expansion, the authors calculated how the mass-loss rate has changed over several thousand years and showed that it agrees with models of thermal pulses. The results will help to understand how evolved stars enrich the interstellar medium with heavy elements.

    Astron. Astrophys. 605, A116 (2017).