Catálogo de publicaciones - revistas

<jats:title>One guanosine determines transcript fate</jats:title> <jats:p> Transcripts of the HIV-1 RNA genome can be either spliced and translated into viral proteins or packaged into new virions as a progeny genome. The path taken depends on whether the transcript contains one guanosine at the 5′ terminus (1G) rather than two or three (2G or 3G). Brown <jats:italic>et al.</jats:italic> used nuclear magnetic resonance spectroscopy to show that 1G transcripts adopt a dimeric structure that sequesters a terminal cap required for translation and splicing but exposes sites that bind to the HIV-1 Gag protein, which recruits the genome during viral assembly. Conversely, 2G or 3G transcripts have the cap accessible, but Gag-binding sites are sequestered. Therefore, a single guanosine acts as a conformational switch to determine the fate of HIV-1 transcripts. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6489" page="413" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aaz7959">413</jats:related-article> </jats:p>

<jats:title>Local drivers of decline matter</jats:title> <jats:p> Recent studies have reported alarming declines in insect populations, but questions persist about the breadth and pattern of such declines. van Klink <jats:italic>et al.</jats:italic> compiled data from 166 long-term surveys across 1676 globally distributed sites and confirmed declines in terrestrial insects, albeit at lower rates than some other studies have reported (see the Perspective by Dornelas and Daskalova). However, they found that freshwater insect populations have increased overall, perhaps owing to clean water efforts and climate change. Patterns of variation suggest that local-scale drivers are likely responsible for many changes in population trends, providing hope for directed conservation actions. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6489" page="417" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aax9931">417</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6489" page="368" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abb6861">368</jats:related-article> </jats:p>

<jats:title>Across time, but also across space</jats:title> <jats:p> Fossils, especially those from marine systems, have long been used to estimate changes in patterns of diversity over time. However, fossils are patchy in their occurrence, so such temporal estimates generally have not included variations due to space. Such a singular examination has the potential to simplify, or even misrepresent, patterns. Close <jats:italic>et al.</jats:italic> used a spatially explicit approach to measure diversity changes in marine fossils across time and space. They found that, like modern systems, diversity varies considerably across space, with reefs increasing diversity levels. Accounting for this spatial-environmental variation will shed new light on the study of diversity over time. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6489" page="420" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aay8309">420</jats:related-article> </jats:p>

<jats:title>Caught in the act</jats:title> <jats:p> Proton-coupled electron transfer (PCET) is an important process for moving electrons through proteins and requires precise positioning of suitable proton and electron carriers. Kang <jats:italic>et al.</jats:italic> determined a cryo–electron microscopy structure of the active complex formed by ribonucleotide reductase that allows for PCET between two protein subunits over a total distance of ∼35 angstroms. Several interventions that stabilized the radical en route also stabilized the complex and allowed for visualization of the interface between the two subunits and the full network of residues that permit PCET. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6489" page="424" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aba6794">424</jats:related-article> </jats:p>

<jats:title>Some calcium is required for binding</jats:title> <jats:p> The melanocortin-4 receptor (MC4R) coordinates food intake and energy expenditure and is a target for treating obesity. MC4R is an unusual G protein–coupled receptor, in part because it binds either an endogenous agonist or an endogenous antagonist, leading to reduced appetite or increased food intake, respectively. Yu <jats:italic>et al.</jats:italic> determined the structure of MC4R bound to an antagonist (see the Perspective by Chaturvedi and Shukla). This structure revealed a calcium ion coordinated by the receptor and the antagonist. Biochemical studies showed that the calcium ion also increased the affinity for endogenous agonist, which translated into increased potency. The authors also confirm a previous finding that MC4R directly couples to the ion channel Kir7.1 and regulates channel gating. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6489" page="428" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aaz8995">428</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6489" page="369" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abb4393">369</jats:related-article> </jats:p>