This month in Bio-Med Roundup:
- Naqvi et al. showed that damage to a region of the brain called the insula disrupts addiction to cigarette smoking.
- Carlton et al. presented the draft genome sequence of the sexually transmitted pathogen Trichomonas vaginalis.
- Armakolas and Klar reported that a protein that controls left-right asymmetry during development is also involved in the segregation of daughter cells during cell division.
- Zarrin et al. provided evidence that the process by which a lymphocyte specifies antibody production may have evolved by exploiting existing cellular DNA repair mechanisms.
- Molecular Biology
- Cell/Developmental Biology
- Genetics
- Microbiology
- Immunology
- Neuroscience
- Biochemistry
- Botany
MOLECULAR BIOLOGY
A Hexanucleotide Element Directs MicroRNA Nuclear Import (5 January 2007)
H.-W. Hwang, E. A. Wentzel, J. T. Mendell
A six-nucleotide sequence near one end of a small noncoding RNA determines its location in the cell nucleus.
A. Armakolas and A. J. S. Klar
A gene known to control left-right asymmetry during development also regulates whether a mouse chromosome segregates randomly during cell division.
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Distinct Populations of Primary and Secondary Effectors During RNAi in C. elegans (12 January 2007)
J. Pak and A. Fire
Secondary siRNAs Result from Unprimed RNA Synthesis and Form a Distinct Class (12 January 2007)
T. Sijen, F. A. Steiner, K. L. Thijssen, R. H. A. Plasterk
In RNA-directed gene silencing in worms, an unanticipated class of small antisense RNAs is synthesized by cellular RNA-directed RNA polymerase.
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CELL/DEVELOPMENTAL BIOLOGY
Differential Transmission of Actin Motion Within Focal Adhesions (5 January 2007)
K. Hu, L. Ji, K. T. Applegate, G. Danuser, C. M. Waterman-Storer
Adhesions on a cell membrane act as molecular clutches to transmit forces from the actin cytoskeleton within a cell to the extracellular substrate, directing cell movement.
I. A. Yudushkin, A. Schleifenbaum, A. Kinkhabwala, B. G. Neel, C. Schultz, P. I. H. Bastiaens
Fluorescence imaging microscopy can distinguish enzyme molecules within a single cell that are actively involved in signaling versus ones that are being deactivated.
V. Kölsch et al.
Furrow formation is initiated during gastrulation when a protein in the outer membrane of epithelial cells binds a cytoskeletal modulator, constricting the outer part of the cells.
Histocompatible Embryonic Stem Cells by Parthenogenesis (26 January 2007)
K. Kim, P. Lerou, A. Yabuuchi, C. Lengerke, K. Ng, J. West, A. Kirby, M. J. Daly, G. Q. Daley
Mouse embryos that develop by parthenogenesis can be a source of embryonic stem cells immunologically compatible with the donor.
Asymmetric Inheritance of Mother Versus Daughter Centrosome in Stem Cell Division (26 January 2007)
Y. M. Yamashita, A. P. Mahowald, J. R. Perlin, M. T. Fuller
In the process of producing differentiating daughters, the mother centrosome of Drosophila male germ cells is anchored via a microtubule array near the niche, producing asymmetric division.
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Kinetics of Morphogen Gradient Formation (26 January 2007)
A. Kicheva, P. Pantazis, T. Bollenbach, Y. Kalaidzidis, T. Bittig, F. Jülicher, M. González-Gaitán
The kinetic parameters that establish and maintain morphogenic gradients are defined and measured for two key morphogens in Drosophila.
GENETICS
Cross-Species Identification of Mendel’s I Locus (5 January 2007)
I. Armstead, I. Donnison, S. Aubry, J. Harper, S. Hörtensteiner, C. James, J. Mani, M. Moffet, H. Ougham, L. Roberts et al.
A homolog of the grass gene staygreen is responsible for one of the traits studied by Mendel in the pea and causes the autumnal loss of green color in monocots and dicots.
High-Throughput Identification of Catalytic Redox-Active Cysteine Residues (19 January 2007)
D. E. Fomenko et al.
Screening of genome databases for bound cysteine-selenocysteine pairs has identified known proteins with redox-active cysteines and predicts previously unknown ones.
A "Silent" Polymorphism in the MDR1 Gene Changes Substrate Specificity (26 January 2007)
C. Kimchi-Sarfaty, J. M. Oh, I.-W. Kim, Z. E. Sauna, A. Maria Calcagno, S. V. Ambudkar, M. M. Gottesman
A rare, but synonymous, codon in alleles of a drug-resistance gene can change translation kinetics and so produce a conformationally distinct protein species.
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MICROBIOLOGY
Draft Genome Sequence of the Sexually Transmitted Pathogen Trichomonas vaginalis (12 January 2007)
J. M. Carlton, R. P. Hirt, J. C. Silva, A. L. Delcher, M. Schatz, Q. Zhao, J. R. Wortman, S. L. Bidwell, U. C. M. Alsmark, S. Besteiro et al.
A common human parasite has an unusually large and repetitive genome that contains many genes originally from bacteria and viruses.
Physiological Proteomics of the Uncultured Endosymbiont of Riftia pachyptila (12 January 2007)
S. Markert, C. Arndt, H. Felbeck, D. Becher, S. M. Sievert, M. Hügler, D. Albrecht, J. Robidart, S. Bench, R. A. Feldman et al.
A proteomic survey of an endosymbiotic bacterium from a hydrothermal vent worm reveals its unusual sulfide oxidation and carbon fixation pathways.
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An H-NS–like Stealth Protein Aids Horizontal DNA Transmission in Bacteria (12 January 2007)
M. Doyle, M. Fookes, A. Ivens, M. W. Mangan, J. Wain, C. J. Dorman
A bacterial gene facilitates horizontal transfer of plasmids to other bacteria by inhibiting the deleterious effects to the recipient’s fitness that would otherwise occur.
F. Not, K. Valentin, K. Romari, C. Lovejoy, R. Massana, K. Töbe, D. Vaulot, L. K. Medlin
A tiny orange eukaryote has been discovered among the plankton of northern seas.
W. W. Lathem, P. A. Price, V. L. Miller, W. E. Goldman
Plague bacteria can infect the lung because of the presence of a specific protease, which probably helps to inhibit host defenses and may be a useful therapeutic target.
A Virus in a Fungus in a Plant: Three-Way Symbiosis Required for Thermal Tolerance (26 January 2007)
L. M. Márquez, R. S. Redman, R. J. Rodriguez, M. J. Roossinck
A heat-tolerant grass in 65ºC Yellowstone soils can grow only when infected by a fungus, which is protective only when it itself is infected by a mycovirus.
IMMUNOLOGY
Differential Antigen Processing by Dendritic Cell Subsets in Vivo (5 January 2007)
D. Dudziak, A. O. Kamphorst, G. F. Heidkamp, V. R. Buchholz, C. Trumpfheller, S. Yamazaki, C. Cheong, K. Liu, H.-W. Lee, C. G. Park et al.
Two different types of dendritic cells in the immune system present antigen in different ways to elicit distinct immune responses.
H. J. Melichar, K. Narayan, S. D. Der, Y. Hiraoka, N. Gardiol, G. Jeannet, W. Held, C. A. Chambers, J. Kang
A transcription factor controls the development of immune cells, supporting growth of one of the two major subsets of T cells while opposing differentiation of the other.
Antibody Class Switching Mediated by Yeast Endonuclease–Generated DNA Breaks (19 January 2007)
A. A. Zarrin et al.
Factors required for the DNA rearrangement that generates antibody classes can be replaced by yeast cleavage-site sequences, pointing to a general DNA repair system.
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Imaging of Germinal Center Selection Events During Affinity Maturation (26 January 2007)
C. D. C. Allen, T. Okada, H. L. Tang, J. G. Cyster
During selection of immune cells that make high-affinity antibodies within lymph nodes, the cells are highly mobile and seem to compete for help from other immune cells.
Balanced Inhibition and Excitation Drive Spike Activity in Spinal Half-Centers (19 January 2007)
R. W. Berg, A. Alaburda, J. Hounsgaard
The neural circuit for scratching in turtles unexpectedly shows periodic waves of simultaneous excitatory and inhibitory synaptic activity, rather than the anticipated alternating oscillations.
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Wandering Minds: The Default Network and Stimulus-Independent Thought (19 January 2007)
M. F. Mason et al.
When the human brain is not engaged by outside stimulation, an active network of cortical areas apparently subserves mind-wandering.
The Neural Basis of Loss Aversion in Decision-Making Under Risk (26 January 2007)
S. M. Tom, C. R. Fox, C. Trepel, R. A. Poldrack
Overlapping brain networks respond more to gambling losses than to gains, correlating with behavioral observations about risk aversion.
Damage to the Insula Disrupts Addiction to Cigarette Smoking (26 January 2007)
N. H. Naqvi, D. Rudrauf, H. Damasio, A. Bechara
Smokers who sustain damage to the insula, a little-studied part of the brain, find that the urge to smoke is reduced.
S. J. Maerkl and S. R. Quake
A microfluidic method for measuring low-affinity molecular interactions characterizes transcription factor binding to DNA.
Nonequilibrium Mechanics of Active Cytoskeletal Networks (19 January 2007)
D. Mizuno, C. Tardin, C. F. Schmidt, F. C. MacKintosh
When the motor protein myosin is added to a gel-like network of cross-linked actin filaments similar to that in cells, the network stiffness increases nearly 100-fold and can then be modified by ATP.
An Inward-Facing Conformation of a Putative Metal-Chelate–Type ABC Transporter (19 January 2007)
H. W. Pinkett, A. T. Lee, P. Lum, K. P. Locher, D. C. Rees
A pump moves molecules out of cells by coupled changes in the nucleotide-binding domain and membrane-spanning helices, which switch the accessibility of the central cavity from outside to inside.
J. D. Murray, B. J. Karas, S. Sato, S. Tabata, L. Amyot, K. Szczyglowski
L. Tirichine, N. Sandal, L. H. Madsen, S. Radutoiu, A. S. Albrektsen, S. Sato, E. Asamizu, S. Tabata, J. Stougaard
In the legume Lotus, symbiotic, nitrogen-fixing bacteria induce formation of the root nodules in which they reside by eliciting a growth response from the plant itself.
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