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Mol Cell. 2008 Jul 11;31(1):67-78. doi: 10.1016/j.molcel.2008.06.002. Epub 2008 Jun 19.

PRG-1 and 21U-RNAs interact to form the piRNA complex required for fertility in C. elegans.

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  • 1Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA.


In metazoans, Piwi-related Argonaute proteins have been linked to germline maintenance, and to a class of germline-enriched small RNAs termed piRNAs. Here we show that an abundant class of 21 nucleotide small RNAs (21U-RNAs) are expressed in the C. elegans germline, interact with the C. elegans Piwi family member PRG-1, and depend on PRG-1 activity for their accumulation. The PRG-1 protein is expressed throughout development and localizes to nuage-like structures called P granules. Although 21U-RNA loci share a conserved upstream sequence motif, the mature 21U-RNAs are not conserved and, with few exceptions, fail to exhibit complementarity or evidence for direct regulation of other expressed sequences. Our findings demonstrate that 21U-RNAs are the piRNAs of C. elegans and link this class of small RNAs and their associated Piwi Argonaute to the maintenance of temperature-dependent fertility.

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