Catálogo de publicaciones - revistas

<jats:title>Dating Wood Rot</jats:title> <jats:p> Specific lineages within the basidiomycete fungi, white rot species, have evolved the ability to break up a major structural component of woody plants, lignin, relative to their non–lignin-decaying brown rot relatives. Through the deep phylogenetic sampling of fungal genomes, <jats:bold> Floudas <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="1715" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1221748">1715</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="6089" page="1649" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1224682">Hittinger</jats:related-article> </jats:bold> ) mapped the detailed evolution of wood-degrading enzymes. A key peroxidase and other enzymes involved in lignin decay were present in the common ancestor of the Agaricomycetes. These genes then expanded through gene duplications in parallel, giving rise to white rot lineages. </jats:p>

<jats:title>Noncanonical Pathway</jats:title> <jats:p> The textbook view of translation of messenger RNA to protein is that it is always initiated from open reading frames (ORFs) that begin with an AUG codon (encodes methionine) by an initiator methionine-bound transfer RNA (tRNA). There is evidence, however, that some polypeptides are produced from non–AUG-initiated ORFs. <jats:bold> Starck <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="1719" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1220270">1719</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="6089" page="1645" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1224439">Dever</jats:related-article> </jats:bold> ) used a variety of biochemical techniques to determine the underlying mechanism for such nontraditional translation initiation. Comparison of translation initiation from AUG-initiated ORFs with those beginning with leucine CUG-initiated ORFs revealed that cells can use an elongator Leu-tRNA to initiate translation at CUG codons. CUG-initiated peptides were presented by major histocompatibility class I molecules and could activate T cells. </jats:p>

<jats:title>Don't Terminate Me!</jats:title> <jats:p> DNA transcription progresses through three phases—initiation, elongation, and termination—of messenger RNA chains. The transcribing enzyme, RNA polymerase (Pol) II, recruits factors that assist in each of these phases. <jats:bold> Mayer <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="1723" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1219651">1723</jats:related-article> ) now show that the C-terminal domain (CTD) of actively elongating Pol II is phosphorylated at conserved tyrosine residues. This modification impairs recruitment of termination factors. Factor exchange on the transcribing polymerase enzyme may be explained by an extended CTD code that is based on differential phosphorylation of the tyrosines and two well-characterized serine residues in the CTD. </jats:p>

<jats:title>Loading a Spring</jats:title> <jats:p> To regulate cellular RNA levels, transcription must be balanced by RNA degradation. An important player is the exosome, which can unwind and degrade structured RNA. <jats:bold> Lee <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="1726" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1216848">1726</jats:related-article> ) used single-molecule fluorescence analysis to investigate how degradation and unwinding are coupled in the catalytic subunit of the yeast exosome complex, Rrp44. Rrp44 apparently digests several base pairs without unwinding, accumulates the energy, which it then uses to unwind four to five base pairs in a burst. Similar spring-like behavior has been proposed for conventional helicases, except that the stored energy comes from hydrolysis of adenosine triphosphate rather than the RNA polymer. </jats:p>

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