Catálogo de publicaciones - revistas

<jats:title>Adaptable DNA Analogs</jats:title> <jats:p> The defining feature of DNA as a genetic blueprint is its capacity for self-replication. In the cell, however, the replication process requires the assistance of multiple elaborate enzymes. How then at the origin of life could DNA or its precursor replicate before enzymes were present? <jats:bold> Ura <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="73" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1174577">73</jats:related-article> , published online 11 June) have achieved the long-sought goal of preparing a synthetic DNA analog that can dynamically adapt its sequence in free solution. Their analog (as yet only studied in relatively short, 20-unit oligomers) replaces DNA's sugar and phosphate backbone by a peptide strand in which cysteines reversibly bind the conventional DNA bases through thioester tethers. These strands can pair with complementary sequences of true DNA and furthermore swap one tethered base for another if different DNA templating strands are added to the solution in succession. </jats:p>

<jats:title>El Niño's Cousin</jats:title> <jats:p> The most energetic and well-known quasi-periodic, air-sea temperature disturbance is ENSO, the mother of the warming of equatorial eastern Pacific surface waters known as El Niño. El Niño, and its cold sister La Niña, can produce dramatic effects on weather across the globe and so it is of great interest and importance to understand it better. Warming in the eastern tropical Pacific is not the only recurring pattern of sea-surface temperature variability in the Pacific, however. <jats:bold> Kim <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="77" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1174062">77</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="47" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1176515">Holland</jats:related-article> </jats:bold> ) report that a pattern of extensive warming in the central Pacific also occurs on a quasi-periodic basis, that it has a large effect on atmospheric circulation, and that it is more predictable than El Niño. These central Pacific warming events have become increasingly more frequent in the last few decades, making it even more vital that we understand them. </jats:p>

<jats:title>Bringing Back the Large Blue</jats:title> <jats:p> Flagship endangered species, such as the Large Blue butterfly have driven conservation programs worldwide. However, the Large Blue butterfly ( <jats:italic>Maculinea arion</jats:italic> ) became extinct in the United Kingdom. The apparent driver of this extinction was a complex set of events documented by Thomas <jats:italic>et al.</jats:italic> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="80" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1175726">80</jats:related-article> , published online 18 June; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="41" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1176892">Settele and Kühn</jats:related-article> ). Life-tables and modeling demonstrate how ecological changes, affecting multiple species, cascaded to negatively impact Large Blue populations. When the changes that cause these extinctions were addressed, reintroduction efforts proved successful. Other insects have experienced similar declines and, hopefully, on sites where their known resources remain abundant, a similar approach may be applied. </jats:p>

<jats:title>Breaking the Barrier</jats:title> <jats:p> Being able to deliver drugs into the brain to treat degenerative diseases such as Alzheimer's or Parkinson's requires the ability to traverse the blood-brain barrier (BBB). Understanding the formation of the very specific adherent junctions (AJ) and tight junctions present at the BBB cell junctions is a prerequisite to the design of such therapeutics. However, diminishing the expression of any one component involved in the formation of these intercellular junctions destroys them. <jats:bold> Coureuil <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="83" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1173196">83</jats:related-article> , published online 11 June) exploited the specific recruitment of AJ proteins by <jats:italic>Neisseria meningitidis</jats:italic> to dissect this process. Adhesion of the bacteria to human brain endothelial cells recruited the polarity complex Par3/Par6/PKCζ required for the establishment of eukaryotic cell polarity and the formation of intercellular junctions. The bacterial recruitment of the polarity complex depleted junctional proteins at the cell-cell interface opening the intercellular junctions at the brainendothelial interface. </jats:p>

<jats:title>Modulating Visual Memory</jats:title> <jats:p> Layer 3 of the secondary visual cortical area V2 plays a role in visual information processing. However, in contrast to layer 3, layer 6 of visual cortex is composed of many types of neurons and their response to visual stimuli is more complex. The importance of layer 6 in visual information processing remains an enigma. <jats:bold> López-Aranda <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="87" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1170869">87</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="40" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1177156">Saksida</jats:related-article> </jats:bold> ) investigated its role in the rat visual cortex in the processing of both short- and long-term visual memory. Elimination of neurons from layer 6 of area V2 led to complete loss of normal memory. However, overexpression of a protein called RGS-14 in the same area boosted the visual memory capacity in such a way that the animals retained the visual information for many months, rather than the normal 45 minutes. </jats:p>

<jats:title>Modifying the Modifier</jats:title> <jats:p> Covalent modification of proteins provides an important means whereby their function is regulated. Hydroxylation, catalyzed by oxygenase enzymes, plays an important role in the response to hypoxia, for example. The human protein Jmjd6 has been thought to act as an oxygenase, catalyzing the demethylation of histone H3 at arginine-2 and histone H4 at arginine-3. <jats:bold> Webby <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="90" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1175865">90</jats:related-article> ) now show that Jmjd6 interacts with the messenger <jats:bold>RNA</jats:bold> splicing factor U2AF65 and acts to hydroxylate this protein at lysine residues, modifications also seen in vivo. Furthermore, Jmjd6 modulates the alternative splicing of both an endogenous gene and an introduced mini-gene. </jats:p>

<jats:title>Putting the Sugar on Polycomb</jats:title> <jats:p> A wide variety of nuclear and cytosolic proteins in human cells carry an O-linked sugar modification, <jats:italic>N</jats:italic> -acetylglucosamine (GlcNAc), which is added by the highly conserved O-linked GlcNAc transferase, Ogt. <jats:bold> Gambetta <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="93" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1169727">93</jats:related-article> , published online 28 May; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="45" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1177264">Simon</jats:related-article> </jats:bold> ) show that in <jats:italic>Drosophila</jats:italic> , Ogt is encoded by super sex combs, a classic Polycomb group gene known for its role in repressing developmental regulator genes. GlcNAc modification is highly enriched at chromosomal sites bound by Polycomb group proteins, and one of these, Polyhomeotic, is modified by Ogt. Thus, in <jats:italic>Drosophila</jats:italic> , it seems that O-linked GlcNAc has a very specific role to effect Polycomb repression. </jats:p>

<jats:title>Biogenic Amine Receptors</jats:title> <jats:p> Biogenic amines have important effects on behavior in humans and other animals. These agents can act by binding to heterotrimeric guanine nucleotide–binding protein (G protein)–coupled receptors, but can also activate ligand-gated ion channels. <jats:bold> Ringstad <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="96" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1169243">96</jats:related-article> ) explored the family of ion channels that respond to biogenic amines in the worm <jats:italic>Caenorhabditis elegans</jats:italic> and characterized two family members that appear to function as chloride channels. One was a receptor activated by dopamine that could bind drugs used in humans as antipsychotics. The other was activated by tyramine and was shown in genetic studies to modulate behavior. Thus, the worm family of biogenic amine–activated channels is larger than previously recognized. If the same is true in humans, related channels may account, in part, for effects of currently used drugs or could be beneficial targets for development of therapeutics. </jats:p>

<jats:title>Idolizing Cholesterol Control</jats:title> <jats:p> The low-density lipoprotein receptor (LDLR) removes LDL, the so-called “bad” cholesterol particles, from the blood through a mechanism that involves LDL binding and internalization into liver cells. Because the LDLR plays a pivotal role in heart disease risk, there is substantial interest in understanding how its expression is regulated, and a large body of previous work has established the importance of transcriptional control. A new study identifies a signaling pathway that appears to regulate the LDLR at the level of protein degradation. <jats:bold> Zelcer <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="100" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1168974">100</jats:related-article> , published online 11 June) show that a sterol-responsive transcription factor called LXR induces the expression of Idol (for inducible degrader of the LDLR), a protein that triggers ubiquitination of the receptor and targets it for degradation. Activation of this pathway suppresses cellular uptake of LDL and, in a mouse model, leads to higher plasma LDL levels, raising the possibility that the pathway could be targeted pharmacologically to control plasma cholesterol levels. </jats:p>

<jats:p>A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.</jats:p>