Bio-Med Roundup

This month in Bio-Med Roundup:
  • Liu et al. described the dynamic movements of HIV reverse transcriptase as it converts viral single-stranded RNA to double-stranded DNA.
  • Stadtfeld et al. and Okita et al. generated mouse induced pluripotent stem cells without viral integration into the genome.
  • Gsponer et al. revealed how disorganized eukaryotic proteins are tightly controlled inside the cell.
  • Haine et al. showed that most bacteria that infect an insect are quickly engulfed by phagocytic cells, before the deployment of antimicrobial peptides, a system that likely curtails bacterial resistance.
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BIOCHEMISTRY
 
Bioactive Contaminants Leach from Disposable Laboratory Plasticware (7 November 2008)
G. R. McDonald et al.
A lipid molecule and a quaternary ammonium biocide that are used in making plastic labware can contaminate common enzyme and binding assays, altering the results.

Insights into Translational Termination from the Structure of RF2 Bound to the Ribosome (7 November 2008)
A. Weixlbaumer et al.
The structure of a release factor bound to an RNA stop codon shows which amino acids form the binding site for U in the first position, A or G in the second, and U in the third.
See related Perspective.

Slide into Action: Dynamic Shuttling of HIV Reverse Transcriptase on Nucleic Acid Substrates (14 November 2008)
S. Liu, E. A. Abbondanzieri, J. W. Rausch, S. F. J. Le Grice, X. Zhuang
As it converts viral single-stranded RNA to double-stranded DNA, HIV reverse transcriptase shuttles between the ends of the nucleic acid, flipping its orientation.
See related Perspective.

The 2.6 Angstrom Crystal Structure of a Human A2A Adenosine Receptor Bound to an Antagonist (21 November 2008)
V.-P. Jaakola et al.
The ligand binding pocket of the caffeine-binding human adenosine receptor has a different position and orientation than that of other G protein–linked receptors.

Tight Regulation of Unstructured Proteins: From Transcript Synthesis to Protein Degradation (28 November 2008)
J. Gsponer, M. E. Futschik, S. A. Teichmann, M. M. Babu
Yeast proteins with unstructured regions tend to be highly regulated, consistent with the idea that these regions may mediate critical regulatory protein-protein interactions.
See related Perspective.

Structural Evidence for Common Ancestry of the Nuclear Pore Complex and Vesicle Coats (28 November 2008)
S. G. Brohawn, N. C. Leksa, E. D. Spear, K. R. Rajashankar, T. U. Schwartz
The protein complex that controls entry and exit from the cell nucleus shares a structural element with vesicle coat proteins, suggesting that it is built around a lattice-like scaffold.


CELL/DEVELOPMENTAL BIOLOGY

Global Protein Stability Profiling in Mammalian Cells (7 November 2008)
H.-C. S. Yen, Q. Xu, D. M. Chou, Z. Zhao, S. J. Elledge
Identification of SCF Ubiquitin Ligase Substrates by Global Protein Stability Profiling (7 November 2008)
H.-C. S. Yen and S. J. Elledge
A method that determines the half lives of all cellular proteins has been used to identify targets of a ubiquitin ligase, which controls the cell cycle through protein degradation.
See related Perspective.

Induced Pluripotent Stem Cells Generated Without Viral Integration (7 November 2008)
M. Stadtfeld, M. Nagaya, J. Utikal, G. Weir, K. Hochedlinger
Transient exposure of mouse fibroblast and liver cells to adenovirus vectors carrying factors that induce pluripotency generates stem cells without viral elements in the genome.

Generation of Mouse Induced Pluripotent Stem Cells Without Viral Vectors (7 November 2008)
K. Okita, M. Nakagawa, H. Hyenjong, T. Ichisaka, S. Yamanaka
Pluripotent cells can be created by introducing transcription factor genes into mouse embryonic fibroblasts on a plasmid that does not integrate into the genome.

Reconstruction of Zebrafish Early Embryonic Development by Scanned Light Sheet Microscopy (14 November 2008)
P. J. Keller, A. D. Schmidt, J. Wittbrodt, E. H. K. Stelzer
Digitized tracking of each cell during the first 24 hours of zebrafish development reveals how the body axis and germ layer are formed and provides a community resource.

Ubiquitin-Like Protein Involved in the Proteasome Pathway of Mycobacterium tuberculosis (14 November 2008)
M. J. Pearce, J. Mintseris, J. Ferreyra, S. P. Gygi, K. H. Darwin
A prokaryotic version of ubiquitin, a eukaryotic tag for protein degradation, is linked to lysines in prokaryotic proteins destined for destruction, a process called pupylation.
See related Perspective.

Regulation of Microtubule Dynamics by Reaction Cascades Around Chromosomes (21 November 2008)
C. A. Athale et al.
A reaction-diffusion model involving regulatory molecules and a microtubule-stabilizing phosphoprotein predicts the spatial distribution of microtubules during cell division.

Canonical Wnt Signaling Regulates Organ-Specific Assembly and Differentiation of CNS Vasculature (21 November 2008)
J. M. Stenman et al.
In mice, two specialized ligands for a key developmental signaling pathway are produced by neuroepithelial cells and direct endothelial cells to form the blood-brain barrier.
See related Perspective.

Detection of GTP-Tubulin Conformation in Vivo Reveals a Role for GTP Remnants in Microtubule Rescues (28 November 2008)
A. Dimitrov et al.
GTP-bound tubulin is found at microtubule ends in living cells and also within microtubules, where it may promote repolymerization and avert microtubule collapse.

Absence of the SRC-2 Coactivator Results in a Glycogenopathy Resembling Von Gierke’s Disease (28 November 2008)
A. R. Chopra et al.
In mice, a coactivator binds to a nuclear orphan receptor and regulates glucose-6-phosphatase transcription and thus glucose homeostasis.


MICROBIOLOGY

Genome of an Endosymbiont Coupling N2 Fixation to Cellulolysis Within Protist Cells in Termite Gut (14 November 2008)
Y. Hongoh et al.
In the termite gut, an endosymbiotic bacterium fixes atmospheric nitrogen within the cells of its cellulose-digesting host protist, allowing the insect to thrive on wood.

Globally Distributed Uncultivated Oceanic N2-Fixing Cyanobacteria Lack Oxygenic Photosystem II (14 November 2008)
J. P. Zehr et al.
An abundant marine cyanobacteria group fixes nitrogen but lacks the genes for carbon fixation and oxygen production, forcing a reevaluation of nitrogen and carbon cycling.

PA-824 Kills Nonreplicating Mycobacterium tuberculosis by Intracellular NO Release (28 November 2008)
R. Singh et al.
An unusual drug candidate for resistant tuberculosis generates nitrous acid and thus acts as an intracellular nitric oxide donor, augmenting the innate immune system.
See related Perspective.


NEUROSCIENCE

Spontaneous Changes of Neocortical Code for Associative Memory During Consolidation (7 November 2008)
K. Takehara-Nishiuchi and B. L. McNaughton
Memory-specific firing patterns appear in the medial prefrontal cortex when it becomes essential for memory recall, supporting a role for this region in memory consolidation.

Promoting Axon Regeneration in the Adult CNS by Modulation of the PTEN/mTOR Pathway (7 November 2008)
K. K. Park et al.
Reactivation of a key growth control pathway by experimentally deleting an inhibitor can overcome the inability of severed mouse retinal ganglion cells to regenerate.
See related Perspective.

PirB Is a Functional Receptor for Myelin Inhibitors of Axonal Regeneration (7 November 2008)
J. K. Atwal et al.
Proteins embedded in the myelin wrappings of axons inhibit regeneration of injured nerves, in part, by binding to an immunoglobulin-like receptor on growth cones.
See related Perspective.

"Who" Is Saying "What"? Brain-Based Decoding of Human Voice and Speech (7 November 2008)
E. Formisano, F. De Martino, M. Bonte, R. Goebel
Distinct patterns of activity elicited in auditory cortex by different vowels and different speakers allows independent identification of who is speaking and what they are saying.


IMMUNOLOGY
 

Batf3 Deficiency Reveals a Critical Role for CD8α+ Dendritic Cells in Cytotoxic T Cell Immunity (14 November 2008)
K. Hildner et al.
In mice, an identifiable subset of antigen-presenting cells is necessary for a normal immune cell response to viral infection and for efficient rejection of tumor cells.

Del-1, an Endogenous Leukocyte-Endothelial Adhesion Inhibitor, Limits Inflammatory Cell Recruitment (14 November 2008)
E. Y. Choi et al.
An endogenous inhibitor of immune cell adhesion dampens recruitment of immune cells to sites of inflammation.

Antimicrobial Defense and Persistent Infection in Insects (21 November 2008)
E. R. Haine, Y. Moret, M. T. Siva-Jothy, J. Rolff
Flies fight some infections by quickly engulfing bacteria in phagocytic cells then deploying antimicrobial peptides, a system that avoids bacterial resistance.
See related Perspective.


PHYSIOLOGY/MEDICINE

Fat Metabolism Links Germline Stem Cells and Longevity in C. elegans (7 November 2008)
M. C. Wang, E. J. O’Rourke, G. Ruvkun
Longevity in C. elegans resulting from quiescent germline stem cells or reduced insulin signaling is caused by induction of a lipase gene that promotes fat mobilization.
See related Perspective.

Regulation of Pancreatic β Cell Mass by Neuronal Signals from the Liver (21 November 2008)
J. Imai et al.
In obese mice, fat tissue stimulates proliferation of insulin-producing pancreatic cells via a neural relay through the liver, contributing to symptoms of metabolic syndrome.

Genomic Analysis of the Clonal Origins of Relapsed Acute Lymphoblastic Leukemia (28 November 2008)
C. G. Mullighan et al.
The cells responsible for relapse of a particular type of leukemia are often not the same cells that gave rise to the original disease.


MOLECULAR BIOLOGY

Chromosome Alignment and Transvection Are Antagonized by Condensin II (28 November 2008)
T. A. Hartl, H. F. Smith, G. Bosco
A Drosophila protein required for dissolution of homologous chromosome bundles independently prevents long-distance effects of one allele on the transcription of its homolog.

An Epigenetic Role for Maternally Inherited piRNAs in Transposon Silencing (28 November 2008)
J. Brennecke et al.
In Drosophila, small RNAs derived from transposons are inherited from the mother and directly inhibit activation of these potentially detrimental transposons in offspring.


PLANT SCIENCE

Arabidopsis Stomatal Initiation Is Controlled by MAPK-Mediated Regulation of the bHLH SPEECHLESS (14 November 2008)
G. R. Lampard, C. A. MacAlister, D. C. Bergmann
Positive and negative developmental signals that determine the locations of gas-exchanging leaf pores converge on a specific domain within a transcription factor.

Regulatory Genes Control a Key Morphological and Ecological Trait Transferred Between Species (14 November 2008)
M. Kim et al.
A key trait—asymmetric flowers with large petals—moves between flower species when a cluster of regulatory genes is transferred from a hybrid to a recipient parent.

A Genetic Framework for the Control of Cell Division and Differentiation in the Root Meristem (28 November 2008)
R. Dello Ioio et al.
The number of stem cells in plant roots is controlled by an auxin-cytokine feedback loop in which a particular gene integrates signals from both hormones.


SOCIOLOGY

Multi-University Research Teams: Shifting Impact, Geography, and Stratification in Science (21 November 2008)
B. F. Jones, S. Wuchty, B. Uzzi
Over the past 30 years, scientific papers have become increasingly likely to be written by teams of authors from more than one of a small number of elite universities.


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