Specific association of Piwi with rasiRNAs derived from retrotransposon and heterochromatic regions in the Drosophila genome.

By Kuniaki Saito, Kazumichi M. Nishida, Tomoko Mori, Yoshinori Kawamura, K. Miyoshi, Tomoko Nagami, H. Siomi, M. Siomi. Genes & Development, 2006

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In Drosophila, Piwi (P-element-induced wimpy testis), which encodes a protein of the Argonaute family, is essential for germ stem cell self-renewal. Piwi has recently been shown to be a nuclear protein involved in gene silencing of retrotransposons and controlling their mobilization in the male germline. However, little is known about the molecular mechanisms of Piwi-dependent gene silencing. Here we show that endogenous Piwi immunopurified from ovary specifically associates with small RNAs of 25-29 nucleotides in length. Piwi-associated small RNAs were identified by cloning and sequencing as repeat-associated small interfering RNAs (rasiRNAs) derived from repetitive regions, such as retrotransposon and heterochromatic regions, in the Drosophila genome. Northern blot analyses revealed that in vivo Piwi does not associate with microRNAs (miRNAs) and that guide siRNA was not loaded onto Piwi when siRNA duplex was added to ovary lysate. In vitro, recombinant Piwi exhibits target RNA cleavage activity. These data together imply that Piwi functions in nuclear RNA silencing as Slicer by associating specifically with rasiRNAs originating from repetitive targets.

Subfields: Molecular Biology, Plant Science

View Paper: https://www.semanticscholar.org/paper/ee1ed9ab9239aef1ff11b066a90fd426e40f43a2

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Citations in the corpus

An endogenous small interfering RNA pathway in Drosophila (2008, background): “Unlike piRNAs 12,13,18,19 , neither somatic nor germline siRNAs exhibited a pronounced enrichment for sense or antisense species (Supplementary Fig.”
A role for Piwi and piRNAs in germ cell maintenance and transposon silencing in Zebrafish. (2007, background): “The correlation between piRNAs and retroelements indicates that these RNAs may have a role in their activity, as has been suggested for Drosophila rasiRNAs and Piwi-associated RNAs (Aravin et al., 2003; Saito et al., 2006).”
Argonaute proteins: key players in RNA silencing (2008, background): “and are required to silence mobile elements and thereby maintain genome integrit”
Specialized piRNA Pathways Act in Germline and Somatic Tissues of the Drosophila Ovary (2009, background): “In the Drosophila ovary, all three Piwi-family members (Piwi, Aub, and AGO3) are expressed ingermline cells (Brennecke etal., 2007; Coxetal., 2000; Gunawardaneet al., 2007;Harris andMacdonald, 2001; Saito et al., 2006), while Piwi alone is expressed in gonadal somatic cells.”
Small non-coding RNAs in animal development (2008, background): “AGO3, AUB and PIWI bind a family of thousands of small non-coding RNAs, called piRNA”
A three-dimensional view of the molecular machinery of RNA interference (2009, background): “melanogaster ), which has an Asp-Asp-Lys motif, is catalytically activ”
Discrete small RNA-generating loci as master regulators of transposon activity in Drosophila. (2007, neutral): “This model is consistent with the known biochemical properties of Piwi and Argonaute proteins (Lau et al., 2006; Liu et al., 2004; Saito et al., 2006).”
PRG-1 and 21U-RNAs interact to form the piRNA complex required for fertility in C. elegans. (2008, background): “In flies a subgroup of piRNAs, originally termed repeat-associated siRNAs (rasiRNAs), are derived primarily from within repeats and transposons and appear to target transposonsforsilencing(Brenneckeetal.,2007;Gunawardaneetal., 2007; Saito et al., 2006 ).”
DNA methylation of retrotransposon genes is regulated by Piwi family members MILI and MIWI2 in murine fetal testes. (2008, positive): “…RNAs against transposon sequences have been cloned in germlines, and the loss of Piwi family gene expression causes downregulation of these small RNAs in Drosophila, zebrafish, and mice (Saito et al. 2006; Aravin et al. 2007; Brennecke et al. 2007; Gunawardane et al. 2007; Houwing et al. 2007).”
MIWI2 is essential for spermatogenesis and repression of transposons in the mouse male germline. (2007, background): “First, in Drosophila, Piwi proteins have a demonstrated role in the control of transposons (Aravin et al., 2001, 2004; Kalmykova et al., 2005; Saito et al., 2006; Sarot Figure 3.”