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[This Week in Science] Sensing touch without touching

Vie, 03/17/2017 - 00:00
Author: Lynden Archer

[This Week in Science] The lights go on in order

Vie, 03/17/2017 - 00:00
Author: Pamela J. Hines

[This Week in Science] Uridine's rise and fall: Food for thought

Vie, 03/17/2017 - 00:00
Author: Paula A. Kiberstis

[This Week in Science] Heavy hydrogen gets frozen in place

Vie, 03/17/2017 - 00:00
Author: Brent Grocholski

[This Week in Science] Calorimetry reaches an atomic junction

Vie, 03/17/2017 - 00:00
Author: Brent Grocholski

[This Week in Science] Protein aggregation-mediated aging in yeast

Vie, 03/17/2017 - 00:00
Author: L. Bryan Ray

[This Week in Science] Promise and challenges of gene editing

Vie, 03/17/2017 - 00:00
Author: Julia Fahrenkamp-Uppenbrink

[This Week in Science] Nonhuman primates model language evolution

Vie, 03/17/2017 - 00:00
Author: Julia Fahrenkamp-Uppenbrink

[This Week in Science] Melanoma cells talk to keratinocytes

Vie, 03/17/2017 - 00:00
Author: Leslie K. Ferrarelli

[This Week in Science] NK cells in severe asthma: Failed resolution

Vie, 03/17/2017 - 00:00
Author: Angela Colmone

[Editors' Choice] Remote sensing for analyzing smallholder farm yields

Vie, 03/17/2017 - 00:00
Author: Pamela J. Hines

[Editors' Choice] Sand-driven magnetic field

Vie, 03/17/2017 - 00:00
Author: Brent Grocholski

[Editors' Choice] Microaggression actions outpace evidence

Vie, 03/17/2017 - 00:00
Author: Brad Wible

[Editors' Choice] Softening up your target

Vie, 03/17/2017 - 00:00
Author: Stella M. Hurtley

[Editors' Choice] Restacking the deck

Vie, 03/17/2017 - 00:00
Author: Phil Szuromi

[Editors' Choice] Love hormones and mental health

Vie, 03/17/2017 - 00:00
Author: Megan Eldred

[Editors' Choice] Fine-scale structure in higher brain areas

Vie, 03/17/2017 - 00:00
Author: Peter Stern

[Research Article] Structural basis of the day-night transition in a bacterial circadian clock

Vie, 03/17/2017 - 00:00
Circadian clocks are ubiquitous timing systems that induce rhythms of biological activities in synchrony with night and day. In cyanobacteria, timing is generated by a posttranslational clock consisting of KaiA, KaiB, and KaiC proteins and a set of output signaling proteins, SasA and CikA, which transduce this rhythm to control gene expression. Here, we describe crystal and nuclear magnetic resonance structures of KaiB-KaiC,KaiA-KaiB-KaiC, and CikA-KaiB complexes. They reveal how the metamorphic properties of KaiB, a protein that adopts two distinct folds, and the post–adenosine triphosphate hydrolysis state of KaiC create a hub around which nighttime signaling events revolve, including inactivation of KaiA and reciprocal regulation of the mutually antagonistic signaling proteins, SasA and CikA. Authors: Roger Tseng, Nicolette F. Goularte, Archana Chavan, Jansen Luu, Susan E. Cohen, Yong-Gang Chang, Joel Heisler, Sheng Li, Alicia K. Michael, Sarvind Tripathi, Susan S. Golden, Andy LiWang, Carrie L. Partch

[Report] Structures of the cyanobacterial circadian oscillator frozen in a fully assembled state

Vie, 03/17/2017 - 00:00
Cyanobacteria have a robust circadian oscillator, known as the Kai system. Reconstituted from the purified protein components KaiC, KaiB, and KaiA, it can tick autonomously in the presence of adenosine 5′-triphosphate (ATP). The KaiC hexamers enter a natural 24-hour reaction cycle of autophosphorylation and assembly with KaiB and KaiA in numerous diverse forms. We describe the preparation of stoichiometrically well-defined assemblies of KaiCB and KaiCBA, as monitored by native mass spectrometry, allowing for a structural characterization by single-particle cryo–electron microscopy and mass spectrometry. Our data reveal details of the interactions between the Kai proteins and provide a structural basis to understand periodic assembly of the protein oscillator. Authors: Joost Snijder, Jan M. Schuller, Anika Wiegard, Philip Lössl, Nicolas Schmelling, Ilka M. Axmann, Jürgen M. Plitzko, Friedrich Förster, Albert J. R. Heck

[Report] Aggregation of the Whi3 protein, not loss of heterochromatin, causes sterility in old yeast cells

Vie, 03/17/2017 - 00:00
In yeast, heterochromatin silencing is reported to decline in aging mother cells, causing sterility in old cells. This process is thought to reflect a decrease in the activity of the NAD+ (oxidized nicotinamide adenine dinucleotide)–dependent deacetylase Sir2. We tested whether Sir2 becomes nonfunctional gradually or precipitously during aging. Unexpectedly, silencing of the heterochromatic HML and HMR loci was not lost during aging. Old cells could initiate a mating response; however, they were less sensitive to mating pheromone than were young cells because of age-dependent aggregation of Whi3, an RNA-binding protein controlling S-phase entry. Removing the polyglutamine domain of Whi3 restored the pheromone sensitivity of old cells. We propose that aging phenotypes previously attributed to loss of heterochromatin silencing are instead caused by aggregation of the Whi3 cell cycle regulator. Authors: Gavin Schlissel, Marek K. Krzyzanowski, Fabrice Caudron, Yves Barral, Jasper Rine

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