Catálogo de publicaciones - revistas

<jats:title>Primary architecture of chromatin fibers</jats:title> <jats:p> The organization of chromosomal DNA, including the positioning of nucleosomes and nucleosome-free regions harboring regulatory proteins along single chromatin fibers, is fundamental to genome function. However, most sequencing methods cannot elucidate this organization at the nucleotide level. Stergachis <jats:italic>et al.</jats:italic> present an approach, Fiber-seq, that maps chromatin fibers onto the underlying DNA template using methyltransferases to create a kind of stencil in fly and human cells. This method identifies chromatin structure at nearly a single-molecule level and can monitor the position of nucleosomes. Using Fiber-seq, the authors identify how regulatory DNA activation is related to nucleosome positioning and DNA variation. </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="6498" page="1449" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aaz1646">1449</jats:related-article> </jats:p>

<jats:title>A blueprint to understand cohesin</jats:title> <jats:p> Cohesin is a multiprotein complex that entraps sister chromatids for chromosome segregation and regulates transcription by extruding DNA loops to shape DNA organization. Shi <jats:italic>et al.</jats:italic> determined the structure of human cohesin bound to the protein NIBPL, which helps load cohesin onto DNA, and DNA at medium resolution by cryo–electron microscopy. Two adenosine triphosphatase domains play a key role in cohesin function. The structure explains how NIBPL and DNA synergistically activate these domains and gives insight into how DNA is trapped by cohesin. </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="6498" page="1454" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abb0981">1454</jats:related-article> </jats:p>

<jats:title>Engaging the nucleosome</jats:title> <jats:p> Cell identity is defined by gene expression patterns that are established through the binding of specific transcription factors. However, nucleosomal units limit access of transcription factors to specific DNA motifs within the mammalian genome. To study how transcription factors bind such chromatinized, nucleosome-embedded motifs, Michael <jats:italic>et al.</jats:italic> focused on the pluripotency factors OCT4 and SOX2. They systematically quantified the relative affinities of these factors at different motif positions throughout the nucleosome, enabling structure determination of OCT4-SOX2–bound nucleosomes by cryo–electron microscopy. OCT4 and SOX2 bound cooperatively to strengthen DNA-binding affinity and resulted in DNA distortions that destabilized the nucleosome. This analysis reveals position-dependent binding modes that were validated in vivo, providing insights on how transcription factors read out chromatinized motifs. </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="6498" page="1460" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abb0074">1460</jats:related-article> </jats:p>

<jats:title>DNA circular dichroism in gas phase</jats:title> <jats:p> Circular dichroism spectroscopy is widely used to distinguish between nonidentical mirror-image molecules. The technique relies on differential absorption of left versus right circularly polarized light and therefore tends to require solution-phase samples for adequate sensitivity. Daly <jats:italic>et al.</jats:italic> now report gas-phase circular dichroism spectra of DNA oligonucleotides based on detection of photodetached electrons rather than transmitted light (see the Perspective by Barran). The salient spectral features matched those in solution. Pairing the technique with mass spectrometry enables prior mass selection of particular molecules for analysis. </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="6498" page="1465" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abb1822">1465</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6498" page="1426" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abc1294">1426</jats:related-article> </jats:p>

<jats:title>The flow of plasma inside the Sun</jats:title> <jats:p> The activity of the Sun, including the occurrence of sunspots, is driven by magnetic fields that originate from the motion of charged plasma beneath the surface. Helioseismology uses acoustic oscillations to probe the Sun's interior, analogous to seismology's use of earthquakes to investigate Earth's interior. Gizon <jats:italic>et al.</jats:italic> analyzed helioseismology data from 1996 to 2019, covering two 11-year solar cycles. They measured the latitudinal and radial flow of plasma as a function of depth within the Sun and how it varies with time. The results support magnetic flux-transport dynamo models, which can explain the distribution of sunspots over each solar cycle. </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="6498" page="1469" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aaz7119">1469</jats:related-article> </jats:p>

<jats:title>Groovy chiral gold particles</jats:title> <jats:p> Although plasmonic optical activity can arise from chiral assemblies of gold and silver nanoparticles, there are few examples of gold nanoparticles with intrinsic chirality and high optical activity. González-Rubio <jats:italic>et al.</jats:italic> show that morphological chirality can be induced during the seeded growth of gold nanoparticles, particularly for highly anisotropic nanorods. Chiral additives as cosurfactants formed helical micelles that directed the seeded growth to create grooves that maintained a chiral morphology. The resulting particles displayed high-intensity circular dichroism with anisotropy factors near 0.2 at near-infrared wavelengths. </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="6498" page="1472" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aba0980">1472</jats:related-article> </jats:p>

<jats:title>A nearby multiplanet system</jats:title> <jats:p> Exoplanets can interact gravitationally with other objects orbiting the same star, affecting their evolution and stability. Studying these effects requires locating systems with multiple planets. Monitoring the nearby red dwarf star GJ 887, Jeffers <jats:italic>et al.</jats:italic> detected periodic radial velocity signals, indicating the presence of two planets on orbits with periods of about 9 and 22 days and a further candidate planet (see the Perspective by Davies). The inclinations of the orbits are unknown, so only minimum masses could be determined, but those were consistent with both planets being super-Earths—more massive than Earth but less than Neptune. This system is only 3.3 parsecs from the Sun, which should facilitate follow-up with other techniques. </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="6498" page="1477" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aaz0795">1477</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6498" page="1432" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abb0217">1432</jats:related-article> </jats:p>