Catálogo de publicaciones - revistas

<jats:title>Mapping Mantle Mixing</jats:title> <jats:p> Mantle convection is the primary driving force for plate tectonics, but mantle convection also mixes material in the interior of Earth and controls heat flow from the core. The patterns of convection are often difficult to image directly with seismic waves—particularly on a global scale. <jats:bold> French <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6155" page="227" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1241514">227</jats:related-article> , published online 5 September) constructed a global tomographic model of the upper mantle and transition zone that is sensitive to changes in seismic velocity and anisotropy. The approach identifies elongated, horizontal structures in the upper mantle that are parallel to overlying plate motions. At greater depths, however, vertical plume-like structures extend from the lower mantle and disappear near the base of low velocity zones like those observed beneath Hawaii. </jats:p>

<jats:title>Viral Defenses</jats:title> <jats:p> In plants and invertebrates, RNA interference (RNAi) functions as an innate antiviral defense mechanism. Viruses that infect plants and invertebrates have evolved viral suppressors of RNAi (VSRs) that disable the RNAi pathway. Whether mammals use RNAi as a defense against viruses has been less clear (see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6155" page="207" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1245475"> <jats:bold>Sagan</jats:bold> and </jats:related-article> <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6155" page="207" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1245475">Sarnow</jats:related-article> </jats:bold> ). <jats:bold> Li <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6155" page="231" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1241911">231</jats:related-article> ) and <jats:bold> Maillard <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6155" page="235" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1241930">235</jats:related-article> ) studied mammalian cell lines and baby mice productively infected with RNA viruses and observed the production of virus-derived small RNAs (vsRNAs). When the putative VSR proteins of the infecting viruses were disabled, host RNAi-derived vsRNAs were much increased and the viruses were rapidly cleared and unable to mount a full-blown infection. Thus, RNAi also has an innate antiviral function in mammals. </jats:p>

<jats:title>Viral Defenses</jats:title> <jats:p> In plants and invertebrates, RNA interference (RNAi) functions as an innate antiviral defense mechanism. Viruses that infect plants and invertebrates have evolved viral suppressors of RNAi (VSRs) that disable the RNAi pathway. Whether mammals use RNAi as a defense against viruses has been less clear (see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6155" page="207" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1245475"> <jats:bold>Sagan</jats:bold> and </jats:related-article> <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6155" page="207" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1245475">Sarnow</jats:related-article> ). Li <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6155" page="231" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1241911">231</jats:related-article> ) and <jats:bold> Maillard <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6155" page="235" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1241930">235</jats:related-article> ) studied mammalian cell lines and baby mice productively infected with RNA viruses and observed the production of virus-derived small RNAs (vsRNAs). When the putative VSR proteins of the infecting viruses were disabled, host RNAi-derived vsRNAs were much increased and the viruses were rapidly cleared and unable to mount a full-blown infection. Thus, RNAi also has an innate antiviral function in mammals. </jats:p>

<jats:title>RTEL1 in DNA Replication</jats:title> <jats:p> Genome stability requires the coordinate action of a variety of DNA maintenance systems. The DNA helicase, RTEL1 (regulator of telomere length 1), disassembles recombination intermediates to avoid dangerous by-products. RTEL1 also limits excessive meiotic crossing over and disassembles telomere T loops. <jats:bold> Vannier <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6155" page="239" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1241779">239</jats:related-article> ) now show that mammalian RTEL1 is part of the DNA replication machinery. RTEL1 binds to proliferating cell nuclear antigen (PCNA), an interaction that was important for normal DNA replication, replication fork stability, and telomere stability. The RTEL1-PCNA interaction was also critical for protecting cells against tumorigenesis but was not required for telomere T-loop disassembly. </jats:p>

<jats:title>Two Viruses to Bind</jats:title> <jats:p> Structural studies of two different H7N9 influenza viruses isolated from humans—A/Shanghai/1/2013 and A/Anhui/1/2013—which have different amino acid sequences in the receptor binding site, provide data indicating that the virus is in transition with respect to host adaptation. The Shanghai virus was one of the first isolated in humans that binds avian receptor glycans with high affinity, but binds poorly to human receptors. However, the later Anhui isolates can bind both avian and human receptors at high affinity. <jats:bold> Shi <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6155" page="243" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1242917">243</jats:related-article> , published online 5 September) show that four hydrophobic mutations contribute to acquisition of affinity for the human receptor by the virus hemagglutinin (HA) and confirm this effect in binding studies with virus particles. Further comparison of a mutant H7N9 A/Anhui/1/2013 HA with the bird flu H5N1 virus revealed the significance of some of the naturally occurring changes observed in circulating H7N9 viruses, which helps to explain how these viruses have been able to cause many severe human infections in a short time. </jats:p>

<jats:title>Unlucky Lakes</jats:title> <jats:p> The negative consequences of increased loading of nitrogen and phosphorus into aquatic ecosystems are well known. Management strategies aimed at reducing the sources of these excess nutrients, such as fertilizer runoff or sewage outflows, can largely mitigate the increases in nitrogen and phosphorus levels; however, it is unclear if these strategies are influencing other spects of these ecosystems. Using a global lake data set, <jats:bold> Finlay <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6155" page="247" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1242575">247</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="6155" page="205" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1245279">Bernhardt</jats:related-article> </jats:bold> ) found that reducing phosphorus inputs reduced a lake's ability to export reactive nitrogen, exacerbating nitrate pollution. </jats:p>

<jats:title>Bacterial Détente?</jats:title> <jats:p> Type VI secretion systems (T6SS) correspond to dynamic intracellular organelles that are functionally analogous to contractile bacteriophage tails. The T6SS of several bacteria species have been found to be responsible for antagonistic behavior that likely reflects the translocation of toxic proteins (effectors) between cells. <jats:italic>Pseudomonas aeruginosa</jats:italic> is able to sense exogenous T6SS attack and assemble its own T6SS apparatus to launch a retaliatory attack aimed directly at the attacker. Now, <jats:bold> Ho <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6155" page="250" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1243745">250</jats:related-article> ) describe how exogenous attack is sensed in a process that involves membrane disruption and suggest that the T6SS provides a general cellular defense mechanism against not only T6SS but also conjugative DNA elements delivered via the type IV secretion system involved in mating pair formation. </jats:p>

<jats:title> <jats:italic>BCL11A</jats:italic> Variants </jats:title> <jats:p> Recent chromatin mapping data have suggested that trait-associated variants often mark regulatory DNA. However, there has been little rigorous experimental investigation of regulatory variation. <jats:bold> Bauer <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6155" page="253" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1242088">253</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6155" page="206" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1245813"> <jats:bold>Hardison and Blobel</jats:bold> </jats:related-article> ) performed an in-depth study of the <jats:italic>BCL11A</jats:italic> fetal hemoglobin-associated locus. The trait-associated variants revealed a chromatin signature that enhanced erythroid development. The enhancer was required for erythroid expression of <jats:italic>BCL11A</jats:italic> and thus for globin gene expression. </jats:p>

<jats:title>The Origins of Europeans</jats:title> <jats:p> To investigate the genetic origins of modern Europeans, <jats:bold> Brandt <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6155" page="257" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1241844">257</jats:related-article> ) examined ancient mitochondrial DNA (mtDNA) and were able to identify genetic differences in 364 Central Europeans spanning the early Neolithic to the Early Bronze Age. Observed changes in mitochondrial haplotypes corresponded with hypothesized human migration across Eurasia and revealed the complexity of the demographic changes and evidence of a Late Neolithic origin for the European mtDNA gene pool. This transect through time reveals four key population events associated with well-known archaeological cultures, which involved genetic influx into Central Europe from various directions at various times. </jats:p>

<jats:p>The U.S. National Human Genome Research Institute says it can sequence genomes for $5,826 as of April 2013—just 0.006% of the $95.2 million per-genome price tag in September 2001. Commercial entities can do it for even less, and by the end of 2013, the cost could well dip below $1,000. Yet even at that low, low price, whole genome sequencing isn't cheap, at least not when researchers need to decode them by the thousands. Enter exome sequencing. Faster, cheaper, and more easily interpreted than its full-sized counterpart, an exome is to a genome as an abstract is to a research article: concise, information-rich, and easily digested.</jats:p>