Bio-Med Roundup

This month in Bio-Med Roundup:
  • Rasch et al. showed that boosting memory-related neural activity through odor cues during sleep can improve memory performance.
  • Bhattacharya et al. provided evidence that the effect of immune escape on HIV evolution is not as strong as previously thought.
  • Lee et al. revealed that autophagy (cellular self-digestion) plays an important role in viral sensing.
  • Barrangou et al. showed that clustered, variable repeat sequences can be acquired by bacterial genomes from bacteriophage and act like RNA interference to block viral infection.
  • Liu et al. identified the receptor for the plant hormone abscisic acid.
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This Month’s Bio-Med Roundup is sponsored by: Open Biosystems
With RNAi tools for knockdown, cDNAs and ORFs for overexpression, and antibodies for protein detection, Open Biosystems is the leading provider of resources for gene analysis.
NEW for RNAi:
GIPZ Lentiviral shRNAmir libraries targeting all human and mouse genes


NEUROSCIENCE
 
Human Neuroblasts Migrate to the Olfactory Bulb via a Lateral Ventricular Extension (2 March 2007)
M. A. Curtis, M. Kam, U. Nannmark, M. F. Anderson, M. Zetterstrom Axell, C. Wikkelso, S. Holtås, W. M. C. van Roon-Mom, T. Björk-Eriksson, C. Nordborg et al.
As in rodents, adult human neurons born along the fluid-filled ventricles in the brain migrate to the olfactory bulb along a tubelike extension of the ventricle.
 
Anti-Hebbian Long-Term Potentiation in the Hippocampal Feedback Inhibitory Circuit (2 March 2007)
K. P. Lamsa, J. H. Heeroma, P. Somogyi, D. A. Rusakov, D. M. Kullmann
In an unusual form of plasticity, certain synapses in rat interneurons are strengthened if presynaptic activity occurs while the postsynaptic cell is at rest or hyperpolarized.
 
Nucleus Accumbens D2/3 Receptors Predict Trait Impulsivity and Cocaine Reinforcement (2 March 2007)
J. W. Dalley, T. D. Fryer, L. Brichard, E. S. J. Robinson, D. E. H. Theobald, K. Lääne, Y. Peña, E. R. Murphy, Y. Shah, K. Probst et al.
Rats that tend to abuse cocaine have lower dopamine receptor availability even before drug exposure, suggesting that this trait is preexisting and not a result of drug abuse.
 
Odor Cues During Slow-Wave Sleep Prompt Declarative Memory Consolidation (9 March 2007)
B. Rasch, C. Büchel, S. Gais, J. Born
In humans, a new memory formed in the presence of an odor is consolidated faster when the odor is used to induce neural activity in the hippocampus during subsequent sleep.
 
Attention-Like Processes in Drosophila Require Short-Term Memory Genes (16 March 2007)
B. van Swinderen
Like humans, fruit flies show characteristic brain activity when attending to new objects, but those with mutations in short-term memory genes do not.
 
Temporal Frequency of Subthreshold Oscillations Scales with Entorhinal Grid Cell Field Spacing (23 March 2007)
L. M. Giocomo, E. A. Zilli, E. Fransén, M. E. Hasselmo
As rats move about, the oscillation frequencies of cortical neurons arrayed in a grid represent how neural activity maps the rat’s position in space.
 
Emergence of Novel Color Vision in Mice Engineered to Express a Human Cone Photopigment (23 March 2007)
G. H. Jacobs, G. A. Williams, H. Cahill, J. Nathans
Mice engineered to express the human long-wavelength opsin in addition to its own two color vision pigments acquire a new ability to distinguish colors.
 
Top-Down Versus Bottom-Up Control of Attention in the Prefrontal and Posterior Parietal Cortices (30 March 2007)
T. J. Buschman and E. K. Miller
One brain area directs self-initiated attention whereas another directs attention in response to external stimuli, each using its own synchronization frequency.



BIOCHEMISTRY/STRUCTURAL BIOLOGY

Emulating Membrane Protein Evolution by Rational Design (2 March 2007)
M. Rapp, S. Seppälä, E. Granseth, G. von Heijne
Stepwise modifications to a drug efflux pump show how the bacterial dimeric pump may have evolved through duplication and inversion of an ancestral protein domain.
See related Perspective.
 
Structural Insight into the Transglycosylation Step of Bacterial Cell-Wall Biosynthesis (9 March 2007)
A. L. Lovering, L. H. de Castro, D. Lim, N. C. J. Strynadka
The crystal structure of an enzyme essential for bacterial cell wall synthesis will allow structure-based design of new antimicrobial agents.
See related Perspective.
 
The Structural Basis of Ribozyme-Catalyzed RNA Assembly (16 March 2007)
M. P. Robertson and W. G. Scott
A synthetic ribozyme catalyzes the bond formation necessary for RNA synthesis by transition-state stabilization and acid-base catalysis, perhaps as in an early RNA world.
See related Perspective.
 
Crystal Structures of the Adenylate Sensor from Fission Yeast AMP-Activated Protein Kinase (23 March 2007)
R. Townley and L. Shapiro
The crystal structure of a key metabolic regulator reveals how it senses the ratio of ATP to AMP, initiating feedback processes to optimize ATP levels in the cell.
See related Perspective.
 
Structure of Nup58/45 Suggests Flexible Nuclear Pore Diameter by Intermolecular Sliding (23 March 2007)
I. Melcák, A. Hoelz, G. Blobel
Pores in the nuclear envelope consist of tetramers with a variable lateral offset that may allow the opening to be adjusted according to the size of molecules passing through.
 
Computational Design of Peptides That Target Transmembrane Helices (30 March 2007)
H. Yin, J. S. Slusky, B. W. Berger, R. S. Walters, G. Vilaire, R. I. Litvinov, J. D. Lear, G. A. Caputo, J. S. Bennett, W. F. DeGrado
Synthetic peptides can be designed to bind with high affinity and specificity to the regions of membrane proteins that span the lipid bilayer of the cell.
 
Protein Composition of Catalytically Active Human Telomerase from Immortal Cells (30 March 2007)
S. B. Cohen, M. E. Graham, G. O. Lovrecz, N. Bache, P. J. Robinson, R. R. Reddel
Catalytically active human telomerase, which maintains chromosome ends, is composed of two molecules of reverse transcriptase, two of RNA, and two dyskerin proteins.



MEDICINE

LRP6 Mutation in a Family with Early Coronary Disease and Metabolic Risk Factors (2 March 2007)
A. Mani, J. Radhakrishnan, H. Wang, A. Mani, M.-A. Mani, C. Nelson-Williams, K. S. Carew, S. Mane, H. Najmabadi, D. Wu, R. P. Lifton
A mutation in a key signaling pathway causes both coronary artery disease and a metabolic syndrome, explaining why these disorders are often associated with one another.
 
Disrupting the Pairing Between let-7 and Hmga2 Enhances Oncogenic Transformation (16 March 2007)
C. Mayr, M. T. Hemann, D. P. Bartel
Loss of miRNA binding sites in the mRNA for a chromatin-associated protein contributes to its overexpression and consequent cancer promoting ability.
 
Founder Effects in the Assessment of HIV Polymorphisms and HLA Allele Associations (16 March 2007)
T. Bhattacharya, M. Daniels, D. Heckerman, B. Foley, N. Frahm, C. Kadie, J. Carlson, K. Yusim, B. McMahon, B. Gaschen et al.
Reanalysis shows that HIV evolves within infected individuals under selection from the immune system, but that this effect is much less pronounced than had been believed.
See related Perspective.
 
CREB-Binding Protein Modulates Repeat Instability in a Drosophila Model for PolyQ Disease (30 March 2007)
J. Jung and N. Bonini
Transgenic fruit flies show many features of a human triplet repeat disease, including expansion of the repeats, and thus can provide clues for therapeutic intervention.
See related Perspective.



CELL/DEVELOPMENTAL BIOLOGY
 

Reconstitution of DNA Segregation Driven by Assembly of a Prokaryotic Actin Homolog (2 March 2007)
E. C. Garner, C. S. Campbell, D. B. Weibel, R. D. Mullins
DNA movement during prokaryotic cell division can be reconstituted in a cell-free system by an actin-like protein and a DNA binding protein, which form a bipolar spindle.
 
Anaphase Onset Before Complete DNA Replication with Intact Checkpoint Responses (9 March 2007)
J. Torres-Rosell, G. De Piccoli, V. Cordon-Preciado, S. Farmer, A. Jarmuz, F. Machin, P. Pasero, M. Lisby, J. E. Haber, L. Aragón
Unexpectedly, yeast—a widely used organism for cell cycle studies—does not have a mechanism to prevent cell division if DNA replication is still incomplete.
See related Perspective.
 
Tunability and Noise Dependence in Differentiation Dynamics (23 March 2007)
G. M. Süel, R. P. Kulkarni, J. Dworkin, J. Garcia-Ojalvo, M. B. Elowitz
A genetic circuit for bacterial cell differentiation exhibits a surprisingly varied repertoire of dynamic responses that depend on the amount of noise in the component biochemical reactions.
 
Permissive and Instructive Anterior Patterning Rely on mRNA Localization in the Wasp Embryo (30 March 2007)
A. E. Brent, G. Yucel, S. Small, C. Desplan
Even though the head-tail axes of wasps and fruit flies develop similarly, they use two entirely different molecular mechanisms.
 
Regulation of Hepatic Stellate Cell Differentiation by the Neurotrophin Receptor p75NTR (30 March 2007)
M. A. Passino, R. A. Adams, S. L. Sikorski, K. Akassoglou
A receptor for a factor that supports survival of neuronal cells is unexpectedly also required for liver regeneration after damage.
 

IMMUNOLOGY
 

Multiple Functions of the IKK-Related Kinase IKKε in Interferon-Mediated Antiviral Immunity (2 March 2007)
B. R. tenOever, S.-L. Ng, M. A. C., S. M. McWhirter, A. García-Sastre, T. Maniatis
A kinase activated in response to viral infection unexpectedly acts directly on a transcription factor for antiviral genes.
 
Autophagy-Dependent Viral Recognition by Plasmacytoid Dendritic Cells (9 March 2007)
H. K. Lee, J. M. Lund, B. Ramanathan, N. Mizushima, A. Iwasaki
An unexpected function of autophagy (cellular self-digestion) is to unite RNA from infecting viruses with immune recognition molecules to trigger innate immune defenses.
See related Perspective.
 
Asymmetric T Lymphocyte Division in the Initiation of Adaptive Immune Responses (23 March 2007)
J. T. Chang, V. R. Palanivel, I. Kinjyo, F. Schambach, A. M. Intlekofer, A. Banerjee, S. A. Longworth, K. E. Vinup, P. Mrass, J. Oliaro et al.
Upon antigen binding, immune cells generate pathogen-fighting cells from daughters arising close to the antigen and memory cells from daughters away from it.
See related Perspective.


MICROBIOLOGY/VIROLOGY

Local Interactions Select for Lower Pathogen Infectivity (2 March 2007)
M. Boots and M. Mealor
Among caterpillars harboring a virus, the least mobile individuals harbor the least infective viruses, confirming a basic hypothesis about disease transmission.
See related Perspective.
 
Suppression of MicroRNA-Silencing Pathway by HIV-1 During Virus Replication (16 March 2007)
R. Triboulet, B. Mari, Y.-L. Lin, C. Chable-Bessia, Y. Bennasser, K. Lebrigand, B. Cardinaud, T. Maurin, P. Barbry, V. Baillat et al.
To protect itself from host defenses, the RNA virus HIV has evolved a way to dampen the host cell’s RNA-silencing machinery.
 
CRISPR Provides Acquired Resistance Against Viruses in Prokaryotes (23 March 2007)
R. Barrangou, C. Fremaux, H. Deveau, M. Richards, P. Boyaval, S. Moineau, D. A. Romero, P. Horvath
Clustered, variable repeat sequences can be acquired by bacterial genomes from bacteriophage or plasmids and act like RNA interference to block infection by viruses.


PLANT SCIENCE
 

Coupling Diurnal Cytosolic Ca2+ Oscillations to the CAS–IP3 Pathway in Arabidopsis (9 March 2007)
R.-H. Tang, S. Han, H. Zheng, C. W. Cook, C. S. Choi, T. E. Woerner, R. B. Jackson, Z.-M. Pei
An interplay of signaling pathways monitors and controls the diurnal rhythm in intracellular calcium in plant cells, responding to soil calcium levels and transpiration.
 

A G Protein–Coupled Receptor Is a Plasma Membrane Receptor for the Plant Hormone Abscisic Acid (23 March 2007)
X. Liu, Y. Yue, B. Li, Y. Nie, W. Li, W.-H. Wu, L. Ma
The cell surface receptor for an important growth regulator in plants binds to its ligand with high affinity and activates downstream targets.
See related Perspective.
 

Gene Co-Inheritance and Gene Transfer (23 March 2007)
Y. Brandvain, M. S. Barker, M. J. Wade
Unexpectedly, in plant taxa that reproduce by self-pollination or cloning, more mitochondrial genes have shifted to the nucleus than in taxa that reproduce sexually.
 

MOLECULAR BIOLOGY
 

Dynamics of Replication-Independent Histone Turnover in Budding Yeast (9 March 2007)
M. F. Dion, T. Kaplan, M. Kim, S. Buratowski, N. Friedman, O. J. Rando

Histone Replacement Marks the Boundaries of cis-Regulatory Domains (9 March 2007)
Y. Mito, J. G. Henikoff, S. Henikoff
Regions of chromatin that are epigenetically silenced and highly regulated are coated with histones that rapidly bind and release the DNA.
 
A Slicer-Mediated Mechanism for Repeat-Associated siRNA 59 End Formation in Drosophila (16 March 2007)
L. S. Gunawardane, K. Saito, K. M. Nishida, K. Miyoshi, Y. Kawamura, T. Nagami, H. Siomi, M. C. Siomi
Tiny RNAs that silence potentially harmful transposons and repetitive sequences in germ cells are excised from larger RNAs by Argonaute proteins.


This Month’s Bio-Med Roundup is sponsored by: Open Biosystems
With RNAi tools for knockdown, cDNAs and ORFs for overexpression, and antibodies for protein detection, Open Biosystems is the leading provider of resources for gene analysis.
NEW for RNAi:
GIPZ Lentiviral shRNAmir libraries targeting all human and mouse genes