Ribosome Profiling Shows That miR-430 Reduces Translation Before Causing mRNA Decay in Zebrafish

<jats:title>Translation Block</jats:title> <jats:p> MicroRNAs (miRNAs) are small, noncoding RNA genes that are found in the genomes of most eukaryotes, where they play an important role in the regulation of gene expression. Although whether gene activity is repressed by blocking translation of messenger RNA (mRNA) targets, or by promoting their deadenylation and then degradation, has been open to debate. <jats:bold> Bazzini <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="233" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1215704">233</jats:related-article> , published online 15 March) and <jats:bold> Djuranovic <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="237" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1215691">237</jats:related-article> ) looked at early points in the repression reaction in the zebrafish embryo or in Drosophila tissue culture cells, respectively, and found that translation was blocked before target mRNAs were significantly deadenylated and degraded. Thus, miRNAs appear to interfere with the initiation step of translation. </jats:p>