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<jats:title>Structure and function of the spliceosome</jats:title> <jats:p> When RNA is transcribed from DNA in the eukaryotic cell nucleus, the initial transcript includes noncoding introns that must be spliced out. This splicing is done by a complex macromolecular machine, the spliceosome, which comprises five small nuclear RNAs and more than 100 associated proteins. Now, two papers reveal insights into the structure and function of the yeast spliceosome. Yan <jats:italic>et al.</jats:italic> describe a high-resolution structure determined by electron microscopy of a spliceosome complex comprising four RNAs and 37 proteins. Hang <jats:italic>et al.</jats:italic> focus on the catalytic site and show how protein components anchor the transcribed RNA and allow sufficient flexibility to deliver RNA components involved in catalyzing the splicing reaction. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue pp. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6253" page="1182" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac7629">1182</jats:related-article> and <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6253" page="1191" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac8159">1191</jats:related-article> </jats:p>

<jats:title>Structure and function of the spliceosome</jats:title> <jats:p> When RNA is transcribed from DNA in the eukaryotic cell nucleus, the initial transcript includes noncoding introns that must be spliced out. This splicing is done by a complex macromolecular machine, the spliceosome, which comprises five small nuclear RNAs and more than 100 associated proteins. Now, two papers reveal insights into the structure and function of the yeast spliceosome. Yan <jats:italic>et al.</jats:italic> describe a high-resolution structure determined by electron microscopy of a spliceosome complex comprising four RNAs and 37 proteins. Hang <jats:italic>et al.</jats:italic> focus on the catalytic site and show how protein components anchor the transcribed RNA and allow sufficient flexibility to deliver RNA components involved in catalyzing the splicing reaction. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue pp. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6253" page="1182" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac7629">1182</jats:related-article> and <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6253" page="1191" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac8159">1191</jats:related-article> </jats:p>

<jats:title>Making and manipulating a weak-link qubit</jats:title> <jats:p> In superconductors, single particles cannot have energies smaller than the superconducting gap. Yet when two superconductors are separated by a thin nonsuperconducting bridge (the “weak link”), quasi-particles can occupy states that are inside the gap, the so-called Andreev bound states (ABSs). Janvier <jats:italic>et al.</jats:italic> fabricated such a structure out of superconducting aluminum and manipulated the occupation of a pair of ABSs. They observed oscillations in population between two of the energy levels, forming a type of qubit, which they dubbed the Andreev qubit. The results may lead to applications in quantum information processing. </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="6253" page="1199" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab2179">1199</jats:related-article> </jats:p>

<jats:title>Vortices in a superconducting egg crate</jats:title> <jats:p> Near equilibrium phase transitions, physical systems that bear no resemblance to one another can behave in a very similar way. For example, thermodynamic functions follow the same scaling behavior in a magnetic transition as in the seemingly unrelated gas-liquid transition. Does such universality exist in nonequilibrium phase transitions? Poccia <jats:italic>et al.</jats:italic> fabricated a square array of superconducting islands on a metallic surface. They applied a magnetic field, which caused vortices to form in between the islands, and induced a transition from a state in which vortices were stuck to their positions to one where they were able to move. They observed the same scaling behavior that applies to some equilibrium transitions. </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="6253" page="1202" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.1260507">1202</jats:related-article> </jats:p>

<jats:title>Interfering with time</jats:title> <jats:p> The interference pattern arising from light or particles passing through a double slit is a simple experiment that belies the subtleties of interpretation when attempting to describe and understand the effect. For example, determining “which path” the light or particles travel can result in the interference pattern disappearing. Margalit <jats:italic>et al.</jats:italic> present a new take on interferometry using time (see the Perspective by Arndt and Brand). A clock—i.e., the internal state of a cold atom condensate—was coherently split and brought back together to interfere. Making one-half of the clock tick at a different rate resulted in a change in the interference pattern, possibly as a consequence of the time being a “which path” witness. </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="6253" page="1205" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac6498">1205</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6253" page="1168" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aad0683">1168</jats:related-article> </jats:p>

<jats:title>Improving cobalt catalysts</jats:title> <jats:p> Tethering molecular catalysts together is a tried and trusted method for making them easier to purify and reuse. Lin <jats:italic>et al.</jats:italic> now show that the assembly of a covalent organic framework (COF) structure can also improve fundamental catalytic performance. They used cobalt porphyrin complexes as building blocks for a COF. The resulting material showed greatly enhanced activity for the aqueous electrochemical reduction of CO <jats:sub>2</jats:sub> to CO. </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="6253" page="1208" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac8343">1208</jats:related-article> </jats:p>

<jats:title>Faults well oriented for failure</jats:title> <jats:p>A deck of cards will remain motionless while pressed on from above, but easily separates when sheared. Similarly, the ease by which geological faults rupture depends on the geometry of the fault relative to the size and direction of stress. Hardebeck finds that faults are well oriented for failure in subduction zones worldwide, suggesting a low-stress environment (see the Perspective by Bürgmann). Subduction zone faults unleash powerful earthquakes. These estimates on the state of stress constrain potential generation mechanisms of destructive subduction zone earthquakes.</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="6253" page="1213" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac5625">1213</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6253" page="1162" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac9625">1162</jats:related-article> </jats:p>

<jats:title>Changing properties of interneurons</jats:title> <jats:p> Neuronal identity is determined early during development. It is assumed that once a neuron has adopted its identity, this remains stable throughout life. However, Dehorter <jats:italic>et al.</jats:italic> investigated the mechanisms controlling the specification of fast-spiking interneurons. They found that the transcription factor Er81 is crucial for the normal specification of these cells by regulating the expression of a potassium channel subunit. </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="6253" page="1216" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab3415">1216</jats:related-article> </jats:p>

<jats:title>Uptake uptick</jats:title> <jats:p> Has global warming slowed the uptake of atmospheric CO <jats:sub>2</jats:sub> by the Southern Ocean? Landschützer <jats:italic>et al.</jats:italic> say no (see the Perspective by Fletcher). Previous work suggested that the strength of the Southern Ocean carbon sink fell during the 1990s. This raised concerns that such a decline would exacerbate the rise of atmospheric CO <jats:sub>2</jats:sub> and thereby increase global surface air temperatures and ocean acidity. The newer data show that the Southern Ocean carbon sink strengthened again over the past decade, which illustrates the dynamic nature of the process and alleviates some of the anxiety about its earlier weakening trend. </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="6253" page="1221" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab2620">1221</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6253" page="1165" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aad0912">1165</jats:related-article> </jats:p>

<jats:title>Transplanting the wisdom of the mayapple</jats:title> <jats:p>Etoposide, a topoisomerase inhibitor, is used to treat various cancers. However, etoposide isn't that easy to get. Its precursor comes from the very slow-growing mayapple plant. Lau and Sattely used bioinformatics, heterologous enzyme expression, and kinetic characterization, to work out the pathway that makes the precursor in mayapple (see the Perspective by O'Connor). They then successfully transplanted the full biosynthetic pathway into tobacco plants.</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="6253" page="1224" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac7202">1224</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6253" page="1167" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aad1801">1167</jats:related-article> </jats:p>