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Structure of YTH domain in complex with m6A RNA [Biochemistry]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
Methylation of the N6 position of selected internal adenines (m6A) in mRNAs and noncoding RNAs is widespread in eukaryotes, and the YTH domain in a collection of proteins recognizes this modification. We report the crystal structure of the splicing factor YT521-B homology (YTH) domain of Zygosaccharomyces rouxii MRB1 in complex...

Liposome transport by myoVa [Biophysics and Computational Biology]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
Myosin Va is an actin-based molecular motor responsible for transport and positioning of a wide array of intracellular cargoes. Although myosin Va motors have been well characterized at the single-molecule level, physiological transport is carried out by ensembles of motors. Studies that explore the behavior of ensembles of molecular motors...

Ring-like oligomers of synaptotagmin-1 [Neuroscience]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
The synaptic vesicle protein synaptotagmin-1 (SYT) is required to couple calcium influx to the membrane fusion machinery. However, the structural mechanism underlying this process is unclear. Here we report an unexpected circular arrangement (ring) of SYT’s cytosolic domain (C2AB) formed on lipid monolayers in the absence of free calcium ions...

Szilard engine with a single electron [Physics]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
The most succinct manifestation of the second law of thermodynamics is the limitation imposed by the Landauer principle on the amount of heat a Maxwell demon (MD) can convert into free energy per single bit of information obtained in a measurement. We propose and realize an electronic MD based on...

Collapse of an ecological network in Ancient Egypt [Anthropology]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
The dynamics of ecosystem collapse are fundamental to determining how and why biological communities change through time, as well as the potential effects of extinctions on ecosystems. Here, we integrate depictions of mammals from Egyptian antiquity with direct lines of paleontological and archeological evidence to infer local extinctions and community...

Phosphatidylethanolamine and {alpha}-syn homeostasis [Biochemistry]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
Phosphatidylserine decarboxylase, which is embedded in the inner mitochondrial membrane, synthesizes phosphatidylethanolamine (PE) and, in some cells, synthesizes the majority of this important phospholipid. Normal levels of PE can decline with age in the brain. Here we used yeast and worms to test the hypothesis that low levels of PE...

Starch-active polysaccharide monooxygenases [Biochemistry]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
The recently discovered fungal and bacterial polysaccharide monooxygenases (PMOs) are capable of oxidatively cleaving chitin, cellulose, and hemicelluloses that contain β(1→4) linkages between glucose or substituted glucose units. They are also known collectively as lytic PMOs, or LPMOs, and individually as AA9 (formerly GH61), AA10 (formerly CBM33), and AA11 enzymes....

Consequences of increased Aurora B activity [Genetics]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
Aurora B kinase regulates the proper biorientation of sister chromatids during mitosis. Lack of Aurora B kinase function results in the inability to correct erroneous kinetochore–microtubule attachments and gives rise to aneuploidy. Interestingly, increased Aurora B activity also leads to problems with chromosome segregation, and overexpression of this kinase has...

Virus-activated plant siRNAs produced by RDR1 [Plant Biology]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
Antiviral immunity controlled by RNA interference (RNAi) in plants and animals is thought to specifically target only viral RNAs by the virus-derived small interfering RNAs (siRNAs). Here we show that activation of antiviral RNAi in Arabidopsis plants is accompanied by the production of an abundant class of endogenous siRNAs mapped...

Gene conversion polarity in maize [Genetics]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
Nucleotide diversity is greater in maize than in most organisms studied to date, so allelic pairs in a hybrid tend to be highly polymorphic. Most recombination events between such pairs of maize polymorphic alleles are crossovers. However, intragenic recombination events not associated with flanking marker exchange, corresponding to noncrossover gene...

DNA-repair factor TDP2 in HBV cccDNA biogenesis [Microbiology]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
Hepatitis B virus (HBV), the causative agent of chronic hepatitis B and prototypic hepadnavirus, is a small DNA virus that replicates by protein-primed reverse transcription. The product is a 3-kb relaxed circular DNA (RC-DNA) in which one strand is linked to the viral polymerase (P protein) through a tyrosyl–DNA phosphodiester...

On the pressure unfolding of T4 lysozyme [Biophysics and Computational Biology]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
It is well known that high hydrostatic pressures can induce the unfolding of proteins. The physical underpinnings of this phenomenon have been investigated extensively but remain controversial. Changes in solvation energetics have been commonly proposed as a driving force for pressure-induced unfolding. Recently, the elimination of void volumes in the...

Land use and emission impacts of Green Revolutions [Sustainability Science]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
There has been a resurgence of interest in the impacts of agricultural productivity on land use and the environment. At the center of this debate is the assertion that agricultural innovation is land sparing. However, numerous case studies and global empirical studies have found little evidence of higher yields being...

Male bonds in a multilevel society [Anthropology]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
Male relationships in most species of mammals generally are characterized by intense intrasexual competition, with little bonding among unrelated individuals. In contrast, human societies are characterized by high levels of cooperation and strong bonds among both related and unrelated males. The emergence of cooperative male–male relationships has been linked to...

Matrix effects in organic aerosol photochemistry [Earth, Atmospheric, and Planetary Sciences]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
This work explores the effect of the environment on the rate of photolysis of 2,4-dinitrophenol (24-DNP), an important environmental toxin. In stark contrast to the slow photolysis of 24-DNP in an aqueous solution, the photolysis rate is increased by more than an order of magnitude for 24-DNP dissolved in 1-octanol...

NIR regulates early lymphocyte development [Immunology and Inflammation]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
Novel inhibitor of histone acetyltransferase repressor (NIR) is a transcriptional corepressor with inhibitor of histone acetyltransferase activity and is a potent suppressor of p53. Although NIR deficiency in mice leads to early embryonic lethality, lymphoid-restricted deletion resulted in the absence of double-positive CD4+CD8+ thymocytes, whereas bone-marrow-derived B cells were arrested...

Roles of myosins XI in penetration resistance [Plant Biology]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
The rapid reorganization and polarization of actin filaments (AFs) toward the pathogen penetration site is one of the earliest cellular responses, yet the regulatory mechanism of AF dynamics is poorly understood. Using live-cell imaging in Arabidopsis, we show that polarization coupled with AF bundling involves precise spatiotemporal control at the...

Evolution of ibrutinib resistance [Evolution]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
The Bruton tyrosine kinase inhibitor (BTKi) ibrutinib is a new targeted therapy for patients with chronic lymphocytic leukemia (CLL). Ibrutinib is given orally on a continuous schedule and induces durable remissions in the majority of CLL patients. However, a small proportion of patients initially responds to the BTKi and then...

Substratum-induced neuronal differentiation [Chemistry]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
Physical stimuli can act in either a synergistic or antagonistic manner to regulate cell fate decisions, but it is less clear whether insoluble signals alone can direct human pluripotent stem (hPS) cell differentiation into specialized cell types. We previously reported that stiff materials promote nuclear localization of the Yes-associated protein...

Structural adaptations in beetle horns [Evolution]

PNAS Early Edition Articles - Mon, 09/08/2014 - 13:03
The shapes of sexually selected weapons differ widely among species, but the drivers of this diversity remain poorly understood. Existing explanations suggest weapon shapes reflect structural adaptations to different fighting styles, yet explicit tests of this hypothesis are lacking. We constructed finite element models of the horns of different rhinoceros...
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