Catálogo de publicaciones - revistas

<jats:title>Recycle MAP, Rewind Ste5</jats:title> <jats:p> Components of the mitogen-activated protein (MAP) kinase pathway for cell signaling in yeast are reused in related pathways that produce very different biological outcomes. So how does a cell know, for example, whether it should grow or mate? Enter Ste5, the prototypical scaffold protein, which binds the set of components from the mating pathway, presumably to sequester them so they can be activated specifically. But <jats:bold> Zalatan <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="1218" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1220683">1218</jats:related-article> , published online 9 August; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6099" page="1178" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1227747">Davis</jats:related-article> </jats:bold> ) found something rather different. Ste5 is not just an inert support structure; it apparently has an active role in the regulatory pathway as an allosteric inhibitor of the MAP kinase, Fus3. It only unclamps Fus3 function when a signal unique to the mating pathway brings Ste5 to the cell membrane. </jats:p>

<jats:title>Relegated to Accessory</jats:title> <jats:p> Critical aspects of meiosis, the specialized cell division that makes haploid gametes and spores, evolved from those of the normal mitotic cell cycle. In mitosis, the RecA homolog Rad51 is required for the homology-mediated repair of DNA double-strand breaks (DSBs). DSBs play a critical role in chromosome segregation in meiosis. <jats:bold> Cloud <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="1222" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1219379">1222</jats:related-article> ) show that the strand-exchange activity of Rad51 is not required in meiosis. Rather, a second meiosis-specific RecA homolog, Dmc1, carries out the homology search and strand-exchange function that Rad51 performs in mitosis, with Rad51 relegated to enhancing the strand-exchange activity of Dmc1. It appears after the gene duplication event that created Dmc1 from an ancestral Rad51. Rad51 took on an accessory role to Dmc1 in meiosis. </jats:p>

<jats:title>Responding to Light and Heat</jats:title> <jats:p> The protein rhodopsin is sensitive to dim light, but its sensitivity is limited by signals caused by the noise of thermal activation. The basis of this relationship, known as the Barlow correlation, has long been debated. A recent study suggested that thermal activation involves a canonical isomerization reaction. <jats:bold> Gozem <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="1225" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1220461">1225</jats:related-article> ) confirm that isomerization is the rate-limiting step controlling thermal noise, and they provide a molecular understanding of the Barlow correlation. They use quantum mechanics coupled with molecular mechanics to show that the transition state mediating thermal activation has the same electronic structure as the photochemical excited state. </jats:p>

<jats:title>Toxic Neighborhood</jats:title> <jats:p> Bacterial populations are often considered to be driven by gene-centric, selfish dynamics. Superficially, antibiotic production fits this picture as individuals can gain most benefit by inhibiting or killing close relatives with high niche overlap. Contrary to that notion, <jats:bold> Cordero <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="1228" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1219385">1228</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6099" page="1184" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1227512"> <jats:bold>Morlon</jats:bold> </jats:related-article> ) show that bacteria in the wild form social units in which antibiotic production and resistance leads to cooperation within, and antagonism between, populations. A combination of high-throughput interaction screening, molecular genetics, and genomics revealed that antibiotics are produced by only a few members of each population, while all other members are resistant. In the past, lack of knowledge of the ecological structure of microbial populations has led to interpretations of antibiotic production and resistance as being largely driven by short-lived, cyclic invasions of populations by antibiotic-producing resistant bacteria. This work shows that structured, socially cohesive bacterial populations exist in the wild and form organizational patterns similar to those of animal and plant populations. </jats:p>

<jats:title>Oncogenic TACC-tics</jats:title> <jats:p> Human cancers exhibit many types of genomic rearrangements—including some that juxtapose sequences from two unrelated genes—thereby creating fusion proteins with oncogenic activity. Functional analysis of these fusion genes can provide mechanistic insights into tumorigenesis and potentially lead to effective drugs, as famously illustrated by the <jats:italic>BCR-ABL</jats:italic> gene in chronic myelogenous leukemia. <jats:bold> Singh <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="1231" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1220834">1231</jats:related-article> , published online 26 July) identify and characterize a fusion gene present in 3% of human glioblastomas, a deadly brain cancer. In the resultant fusion protein, the tyrosine kinase region of the fibroblast growth factor receptor (FGFR) is joined to a domain from a transforming acidic coiled-coil (TACC) protein. The TACC-FGFR protein is oncogenic, shows unregulated kinase activity, localizes to the mitotic spindle, and disrupts chromosome segregation. In mice, FGFR inhibitors slowed the growth of tumors driven by the TACC-FGFR gene, suggesting that a subset of glioblastoma patients may benefit from these types of drugs. </jats:p>

<jats:p> The 2012 Gordon Research Conference schedule was published on pages 1236 to 1246 of this issue of the print version of <jats:italic>Science</jats:italic> . The current schedule can also be found online at <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://www.grc.org/">www.grc.org/</jats:ext-link> . </jats:p>

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