PerspectiveMolecular Biology

Outsourcing Genome Protection

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Science  03 Aug 2012:
Vol. 337, Issue 6094, pp. 529-530
DOI: 10.1126/science.1227095

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Eukaryotic genomes are populated by invading mobile genetic elements called transposons that threaten genome stability as they may cause mutations and chromosomal rearrangements. In animal germ lines, protection against these parasitic elements is conferred by Piwi proteins and their associated ∼20- to 30-nucleotide small RNA guides, called Piwi-interacting RNAs (piRNAs), which actively repress transposons to safeguard the genetic information (1). On page 574 of this issue, Bagijn et al. (2) reveal how piRNAs in the worm Caenorhabditis elegans identify their transposon targets, triggering local generation of another class of small RNAs, called 22G-RNAs, that carry out silencing. Together with four other reports (36), the study by Bagijn et al. provides a comprehensive view of worm piRNA targets, mechanism of piRNA action, and pathways that discriminate foreign elements from cellular mRNAs.