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  • The EMBO Journal (2009) 28, 2932 - 2944
  • doi:10.1038/emboj.2009.220

Published online: 30 July 2009

  • Subject Category:

Endo-siRNAs depend on a new isoform of loquacious and target artificially introduced, high-copy sequences

Julia Verena Hartig1,4, Stephanie Esslinger1,4, Romy Böttcher1, Kuniaki Saito2 and Klaus Förstemann1,3

  1. Gene Center, Department of Chemistry and Biochemistry, Ludwig-Maximilians-Universität München, Munich, Germany
  2. Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan
  3. Munich Center for Integrated Protein Science (CiPSM), Ludwig-Maximilians-Universität München, Munich, Germany

Correspondence to:

Klaus Förstemann, Gene Center, Department of Chemistry and Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Str. 25, Munich, 81377, Germany. Tel.: +49 89 2180 76912; Fax: +49 89 2180 76945; E-mail: Foerstemann@lmb.uni-muenchen.de

4These authors contributed equally to the work

Received 15 May 2009; Accepted 9 July 2009

Colonization of genomes by a new selfish genetic element is detrimental to the host species and must lead to an efficient, repressive response. In vertebrates as well as in Drosophila, piRNAs repress transposons in the germ line, whereas endogenous siRNAs take on this role in somatic cells. We show that their biogenesis depends on a new isoform of the Drosophila TRBP homologue loquacious, which arises by alternative polyadenylation and is distinct from the one that functions during the biogenesis of miRNAs. For endo-siRNAs and piRNAs, it is unclear how an efficient response can be initiated de novo. Our experiments establish that the endo-siRNA pathway will target artificially introduced sequences without the need for a pre-existing template in the genome. This response is also triggered in transiently transfected cells, thus genomic integration is not essential. Deep sequencing showed that corresponding endo-siRNAs are generated throughout the sequence, but preferentially from transcribed regions. One strand of the dsRNA precursor can come from spliced mRNA, whereas the opposite strand derives from independent transcripts in antisense orientation.

  • Keywords:

    • Drosophila melanogaster,
    • endo-siRNAs,
    • post-transcriptional regulation,
    • RNA interference,
    • transposon silencing