Collapse of germline piRNAs in the absence of Argonaute3 reveals somatic piRNAs in flies
Department of Biochemistry and Molecular Pharmacology; Program in Bioinformatics and Integrative Biology; Program in Molecular Medicine; Department of Molecular Genetics and Microbiology; Graduate School of Biomedical Sciences
Medical Subject Headings
DNA Transposable Elements; Drosophila Proteins; Drosophila melanogaster; RNA Interference; Germ-Line Mutation; Antisense Elements (Genetics); RNA, Antisense; RNA, Small Interfering; RNA-Induced Silencing Complex
Life Sciences | Medicine and Health Sciences
Piwi-interacting RNAs (piRNAs) silence transposons in animal germ cells. piRNAs are thought to derive from long transcripts spanning transposon-rich genomic loci and to direct an autoamplification loop in which an antisense piRNA, bound to Aubergine or Piwi protein, triggers production of a sense piRNA bound to the PIWI protein Argonaute3 (Ago3). In turn, the new piRNA is envisioned to produce a second antisense piRNA. Here, we describe strong loss-of-function mutations in ago3, allowing a direct genetic test of this model. We find that Ago3 acts to amplify piRNA pools and to enforce on them an antisense bias, increasing the number of piRNAs that can act to silence transposons. We also detect a second, Ago3-independent piRNA pathway centered on Piwi. Transposons targeted by this second pathway often reside in the flamenco locus, which is expressed in somatic ovarian follicle cells, suggesting a role for piRNAs beyond the germline.
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Citation: Cell. 2009 May 1;137(3):509-21. Epub 2009 Apr 23. Link to article on publisher's site