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Nuclear PKM2 in EMT [Medical Sciences]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
Pyruvate kinase M2 (PKM2) is an alternatively spliced variant of the pyruvate kinase gene that is preferentially expressed during embryonic development and in cancer cells. PKM2 alters the final rate-limiting step of glycolysis, resulting in the cancer-specific Warburg effect (also referred to as aerobic glycolysis). Although previous reports suggest that...

Nonpyrrolysine glycine betaine methyltransferase [Microbiology]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
COG5598 comprises a large number of proteins related to MttB, the trimethylamine:corrinoid methyltransferase. MttB has a genetically encoded pyrrolysine residue proposed essential for catalysis. MttB is the only known trimethylamine methyltransferase, yet the great majority of members of COG5598 lack pyrrolysine, leaving the activity of these proteins an open question....

Actor contributions to deforestation in the Amazon [Environmental Sciences]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
Annual deforestation rates in the Brazilian Amazon fell by 77% between 2004 and 2011, yet have stabilized since 2009 at 5,000–7,000 km2. We provide the first submunicipality assessment, to our knowledge, of actor-specific contributions to the deforestation slowdown by linking agricultural census and remote-sensing data on deforestation and forest degradation....

Mesophyll diffusion and CO2 fertilization on land [Environmental Sciences]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
In C3 plants, CO2 concentrations drop considerably along mesophyll diffusion pathways from substomatal cavities to chloroplasts where CO2 assimilation occurs. Global carbon cycle models have not explicitly represented this internal drawdown and therefore overestimate CO2 available for carboxylation and underestimate photosynthetic responsiveness to atmospheric CO2. An explicit consideration of mesophyll...

Prion amyloid architecture [Biophysics and Computational Biology]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
The [PSI+] prion is a self-propagating amyloid of the translation termination factor, Sup35p, of Saccharomyces cerevisiae. The N-terminal 253 residues (NM) of this 685-residue protein normally function in regulating mRNA turnover but spontaneously form infectious amyloid in vitro. We converted the three Ile residues in Sup35NM to Leu and then...

Obesity accelerates epigenetic aging [Medical Sciences]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
Because of the dearth of biomarkers of aging, it has been difficult to test the hypothesis that obesity increases tissue age. Here we use a novel epigenetic biomarker of aging (referred to as an “epigenetic clock”) to study the relationship between high body mass index (BMI) and the DNA methylation...

HPV in head and neck cancers [Medical Sciences]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
Previous studies have established that a subset of head and neck tumors contains human papillomavirus (HPV) sequences and that HPV-driven head and neck cancers display distinct biological and clinical features. HPV is known to drive cancer by the actions of the E6 and E7 oncoproteins, but the molecular architecture of...

Phagosome tubulation in dendritic cells [Immunology and Inflammation]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
Dendritic cells (DCs) phagocytose large particles like bacteria at sites of infection and progressively degrade them within maturing phagosomes. Phagosomes in DCs are also signaling platforms for pattern recognition receptors, such as Toll-like receptors (TLRs), and sites for assembly of cargo-derived peptides with major histocompatibility complex class II (MHC-II) molecules....

CO2 dissolution at Bravo Dome [Earth, Atmospheric, and Planetary Sciences]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
The injection of carbon dioxide (CO2) captured at large point sources into deep saline aquifers can significantly reduce anthropogenic CO2 emissions from fossil fuels. Dissolution of the injected CO2 into the formation brine is a trapping mechanism that helps to ensure the long-term security of geological CO2 storage. We use...

Expansion mechanism of T7 phage revealed by cryoEM [Biophysics and Computational Biology]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
Many dsDNA viruses first assemble a DNA-free procapsid, using a scaffolding protein-dependent process. The procapsid, then, undergoes dramatic conformational maturation while packaging DNA. For bacteriophage T7 we report the following four single-particle cryo-EM 3D reconstructions and the derived atomic models: procapsid (4.6-Å resolution), an early-stage DNA packaging intermediate (3.5 Å),...

Sea level and ice volume since the glacial maximum [Earth, Atmospheric, and Planetary Sciences]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
The major cause of sea-level change during ice ages is the exchange of water between ice and ocean and the planet’s dynamic response to the changing surface load. Inversion of ∼1,000 observations for the past 35,000 y from localities far from former ice margins has provided new constraints on the...

IL-33 activation by mast cell proteases [Immunology and Inflammation]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
Interleukin-33 (IL-33) is an alarmin cytokine from the IL-1 family. IL-33 activates many immune cell types expressing the interleukin 1 receptor-like 1 (IL1RL1) receptor ST2, including group-2 innate lymphoid cells (ILC2s, natural helper cells, nuocytes), the major producers of IL-5 and IL-13 during type-2 innate immune responses and allergic airway...

Long-term pesticide applications and soil erosion [Agricultural Sciences]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
Agricultural pesticide use has increased worldwide during the last several decades, but the long-term fate, storage, and transfer dynamics of pesticides in a changing environment are poorly understood. Many pesticides have been progressively banned, but in numerous cases, these molecules are stable and may persist in soils, sediments, and ice....

Virioplankton ribonucleotide reductase [Microbiology]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
Virioplankton play a crucial role in aquatic ecosystems as top-down regulators of bacterial populations and agents of horizontal gene transfer and nutrient cycling. However, the biology and ecology of virioplankton populations in the environment remain poorly understood. Ribonucleotide reductases (RNRs) are ancient enzymes that reduce ribonucleotides to deoxyribonucleotides and thus...

eIF4AIII enhances CBC-dependent translation [Biochemistry]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
It has long been considered that intron-containing (spliced) mRNAs are translationally more active than intronless mRNAs (identical mRNA not produced by splicing). The splicing-dependent translational enhancement is mediated, in part, by the exon junction complex (EJC). Nonetheless, the molecular mechanism by which each EJC component contributes to the translational enhancement...

Double-stranded RNA under force and torque [Biophysics and Computational Biology]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
RNA plays myriad roles in the transmission and regulation of genetic information that are fundamentally constrained by its mechanical properties, including the elasticity and conformational transitions of the double-stranded (dsRNA) form. Although double-stranded DNA (dsDNA) mechanics have been dissected with exquisite precision, much less is known about dsRNA. Here we...

Chlamydomonas repressor of cellular quiescence [Plant Biology]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
Microalgae are prolific photosynthetic organisms that have the potential to sustainably produce high-value chemical feedstocks. However, an industry based on microalgal biomass still is faced with challenges. For example, microalgae tend to accumulate valuable compounds, such as triacylglycerols, only under stress conditions that limit growth. To investigate the fundamental mechanisms...

Lead in the Indian Ocean [Environmental Sciences]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
Humans have injected lead (Pb) massively into the earth surface environment in a temporally and spatially evolving pattern. A significant fraction is transported by the atmosphere into the surface ocean where we can observe its transport by ocean currents and sinking particles. This study of the Indian Ocean documents high...

Hair-bundle morphogenesis [Applied Mathematics]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
The hair bundle, an apical specialization of the hair cell composed of several rows of regularly organized stereocilia and a kinocilium, is essential for mechanotransduction in the ear. Its precise organization allows the hair bundle to convert mechanical stimuli to electrical signals; mutations that alter the bundle’s morphology often cause...

Autism treatment with sulforaphane [Medical Sciences]

PNAS Early Edition Articles - Mon, 10/13/2014 - 13:05
Autism spectrum disorder (ASD), characterized by both impaired communication and social interaction, and by stereotypic behavior, affects about 1 in 68, predominantly males. The medico-economic burdens of ASD are enormous, and no recognized treatment targets the core features of ASD. In a placebo-controlled, double-blind, randomized trial, young men (aged 13–27)...
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