Catálogo de publicaciones - revistas

<jats:title>Riboswitch Revealed</jats:title> <jats:p> Short regulatory regions—riboswitches—are found in the messenger RNAs of many bacteria, plants, and fungi. They bind to small-molecule metabolites and, through switching between alternate RNA secondary structures, regulate the expression of the linked RNA. <jats:bold> Lee <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="845" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1190713">845</jats:related-article> ) have identified a c-di-GMP (cyclic di-guanosyl-5′-monophosphate)–binding riboswitch in the bacterium <jats:italic>Clostridium difficile</jats:italic> that regulates the splicing of a group I self-splicing ribozyme. Binding of c-di-GMP to the riboswitch favors a conformation of the ribozyme that promotes splicing in the presence of guanosine triphosphate (as is typical for this class of ribozymes). Concomitantly, splicing promotes the formation of a ribosome binding site, thereby stimulating protein production from the downstream pathogenesis-related gene. This regulatory region may thus constitute a two-input gene-control system that reads the concentration of both GTP and c-di-GMP. Thus, not all group I self-splicing ribozymes represent selfish genetic elements. </jats:p>

<jats:title>A Gut Feeling</jats:title> <jats:p> Special immune controls are necessary in the gut to prevent the immune system from reacting to the commensal microbiota and to food antigens. Dendritic cells (DCs) are important for maintaining gut tolerance because they help to keep T cells in an unresponsive state. However, in other environments, DCs activate T cells. What signals determine whether DCs induce T cell tolerance or activation? <jats:bold> Manicassamy <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="849" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1188510">849</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5993" page="767" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1194185"> <jats:bold>Mellman and Clausen</jats:bold> </jats:related-article> ) found that β-catenin–dependent signaling is required for maintaining DC-mediated gut tolerance in mice. Wnt ligands were expressed in the gut, and β-catenin signaling was activated in DCs in the small and large intestines but not in the spleen. When β-catenin was specifically deleted from DCs in mice, the frequency of regulatory T cells and anti-inflammatory cytokines was reduced, whereas the frequency of pro-inflammatory T helper 1 and T helper 17 cells and their associated cytokines was increased. Mice lacking β-catenin in dendritic cells also exhibited enhanced susceptibility in a mouse model of colitis. </jats:p>

<jats:title>Building a Network</jats:title> <jats:p> The relation between the architecture of ecological networks and community stability is important to understand the assembly of complex communities. By combining a model approach and a meta-analysis of a large collection of ecological networks, <jats:bold>Thébault and Fontaine</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="853" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1188321">853</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5993" page="765" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1194255">Bascompte</jats:related-article> </jats:bold> ) found that network architecture and stability fundamentally differed between trophic networks that involved herbivory and mutualistic networks that involved pollination. These findings have implications for the understanding of community structure, evolution, and response to perturbation. </jats:p>

<jats:title>Designer Anti-HIV</jats:title> <jats:p> Developing a protective HIV vaccine remains a top global health priority. One strategy to identify potential vaccine candidates is to isolate broadly neutralizing antibodies from infected individuals and then attempt to elicit the same antibody response through vaccination (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5993" page="770" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1194693">Burton and Weiss</jats:related-article> </jats:bold> ). <jats:bold> Wu <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="856" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1187659">856</jats:related-article> , published online 8 July) now report the identification of three broadly neutralizing antibodies, isolated from an HIV-1–infected individual, that exhibited great breadth and potency of neutralization and were specific for the co-receptor CD4-binding site of the glycoprotein 120 (gp120), part of the viral Env spike. <jats:bold> Zhou <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="811" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1192819">811</jats:related-article> , published online 8 July) analyzed the crystal structure for one of these antibodies, VRC01, in complex with an HIV-1 gp120. VRC01 focuses its binding onto a conformationally invariant domain that is the site of initial CD4 attachment, which allows the antibody to overcome the glycan and conformational masking that diminishes the neutralization potency of most CD4-binding-site antibodies. The epitopes recognized by these antibodies suggest potential immunogens that can inform vaccine design. </jats:p>

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