Catálogo de publicaciones - revistas

<jats:title>RNA Wars</jats:title> <jats:p> During RNA interference (RNAi), the Dicer endonuclease generates small interfering (si)RNAs that, with the help of the protein R2D2, are loaded into the siRNA-induced silencing complex (RISC). Using siRNAs as guides, RISC, and specifically its Argonaute subunit, targets complementary RNAs for destruction. In order to identify other components of the RISC complex, <jats:bold> Liu <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="750" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1176325">750</jats:related-article> ) reconstituted the core RISC activity, using purified <jats:italic>Drosophila</jats:italic> Dicer, R2D2, and Ago-2. The protein C3PO (component 3 promoter of RISC), which consists of heterodimer of Translin and Translin-associated factor X (Trax), was found to enhance RISC activity in this system, and in vivo, with the Trax endonuclease activity activating RISC through the removal of siRNA passenger strand cleavage products. </jats:p>

<jats:title>Jamming Protein Translocation</jats:title> <jats:p> Antibiotics are tremendously important drugs in modern medicine, yet we are still learning precisely how they work. SecY is a bacterial membrane protein that is part of a complex that allows protein secretion across the membrane. <jats:bold> Van Stelten <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="753" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1172221">753</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article issue="5941" page="" related-article-type="in-this-issue" vol="325">Breukink</jats:related-article> </jats:bold> ) found in <jats:italic>Escherichia coli</jats:italic> cells that if the protein translocator complex becomes jammed with a protein that cannot pass through, the SecY protein is degraded by the protease FtsH, leading to cell death. Cells could be protected by increasing amounts of an inhibitor of FtsH, the YccA protein. Antibiotics that block protein translation also caused jamming of the SecY machinery and destruction of SecY, thus contributing to cell death. </jats:p>

<jats:title>Fine Dendrites Fire Differently</jats:title> <jats:p> The pyramidal neuron is the basic computational unit in the brain cortex. Its distal tuft dendrite is heavily innervated by horizontal fibers coursing through cortical layer-I providing long-range corticocortical and thalamocortical associational input. <jats:bold> Larkum <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="756" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1171958">756</jats:related-article> ) investigated whether the apical tuft dendrites of layer-5 neocortical pyramidal neurons, like basal dendrites, generate <jats:italic>n</jats:italic> -methyl- <jats:sc>d</jats:sc> -aspartate (NMDA) spikes using two-photon–guided direct dendritic recording, glutamate uncaging, and modeling. NMDA spikes could be evoked in the distal tuft dendrites, while Ca <jats:sup>2+</jats:sup> spikes could be triggered at the bifurcation points. Block of the hyperpolarization-activated current enhanced these NMDA spikes. Thus, the generation of NMDA spikes is a general principle of thin, basal, and tuft dendrites. </jats:p>

<jats:title>Plastic Pain Perception</jats:title> <jats:p> Drugs and endocannabinoids acting on cannabinoid (CB) receptors have potential in the treatment of certain types of pain. In the spinal cord they are believed to suppress nociception, the perception of pain and noxious stimuli. <jats:bold> Pernia-Andrade <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="760" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1171870">760</jats:related-article> ) now find that endocannabinoids, which are released in spinal cord by noxious stimulation, may promote rather than inhibit nociception by acting on CB1 receptors. Endocannabinoids not only depress transmission at excitatory synapses in the spinal cord, but also block the release of inhibitory neurotransmitters, thereby facilitating nociception. </jats:p>

<jats:title>Taking Shape</jats:title> <jats:p> DNA recombination mechanisms enable certain pathogens to modify the proteins on their outer surfaces by rearranging their genes and so avoid repeated detection by the immune system. <jats:bold>Cahoon and Seifert</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="764" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1175653">764</jats:related-article> ) have found that antigenic variation of a single genetic locus in the human pathogen <jats:italic>Neisseria gonorrhoeae</jats:italic> is triggered by a specific cis-acting DNA element. This 16–base pair DNA sequence formed an unusual DNA structure in vitro; a guanine quartet (G4), which has been implicated in only a few other biological processes. The G4 forming sequence is required for processing the gene conversion reaction leading to antigenic variation. These findings have implications both for understanding mechanisms of DNA recombination and its role in microbial pathogenesis. </jats:p>

<jats:p>The show includes designer DNA shapes, new technologies for toxicity testing, the origins of eukaryotes, and more.</jats:p>

<jats:p>A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.</jats:p>