Endogenous siRNAs Derived from Transposons and mRNAs in Drosophila Somatic Cells

Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
Science (Impact Factor: 33.61). 06/2008; 320(5879):1077-81. DOI: 10.1126/science.1157396
Source: PubMed


Small interfering RNAs (siRNAs) direct RNA interference (RNAi) in eukaryotes. In flies, somatic cells produce siRNAs from
exogenous double-stranded RNA (dsRNA) as a defense against viral infection. We identified endogenous siRNAs (endo-siRNAs),
21 nucleotides in length, that correspond to transposons and heterochromatic sequences in the somatic cells of Drosophila melanogaster. We also detected endo-siRNAs complementary to messenger RNAs (mRNAs); these siRNAs disproportionately mapped to the complementary
regions of overlapping mRNAs predicted to form double-stranded RNA in vivo. Normal accumulation of somatic endo-siRNAs requires
the siRNA-generating ribonuclease Dicer-2 and the RNAi effector protein Argonaute2 (Ago2). We propose that endo-siRNAs generated
by the fly RNAi pathway silence selfish genetic elements in the soma, much as Piwi-interacting RNAs do in the germ line.

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Available from: Megha Ghildiyal, May 16, 2014
    • "Introduction to the transformative technology of RNAi: how RNAi is being used in agricultural biotechnology (Munyikwa) Many natural processes in eukaryotic organisms (plants, insects, animals, and nematodes etc.) such as the regulation of gene expression, suppression of invading viruses, and overall protection of the genome have been shown to be mediated by small RNAs. This occurs via a process now universally called RNAi (Fire et al., 1998; Brodersen and Voinnet, 2006; Ghildiyal et al., 2008; Jones-Rhoades et al., 2006; Mallory and Vaucheret, 2006; Huvenne and Smagghe, 2010). The term RNAi was popularized by Fire and Mello following their Nobel Prize winning work in Science or Medicine (2006) which demonstrated the potent effects of double stranded RNA (dsRNA) in Caenorhabditis elegans (Fire et al., 1998) and initiated intense research to understand the mechanisms underlying RNAi and its potential uses. "
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    • "Reviewing previous studies on Drosophila sRNAs we hypothesize that our conclusions drawn on the basis of the tupaia data could also be valid for sRNA silencing pathways in Drosophila. In Drosophila, siRNAs were assumed to silence TEs mainly in the soma, displaying a more or less separation of the siRNA-and piRNA-pathway into soma and germline (Ghildiyal et al. 2008). However, TE-derived si-as well as piRNAs were sequenced from the Drosophila ovary somatic sheet cell line (Lau et al. 2009). "
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    • "Since many endogenous cells in Drosophila (i.e., follicle, nurse, and salivary gland cells) naturally undergo polyploidization, the different ploidy in OSC and OSS cells may be a natural characteristic. Many Drosophila cell cultures are persistently infected with viruses, such as Drosophila S2 cells (Aliyari et al. 2008; Czech et al. 2008; Ghildiyal et al. 2008; Kawamura et al. 2008; Flynt et al. 2009; Goic et al. 2013) as well as OSS cells (Wu et al. 2010). Drosophila cells stem this viral overload with RNA interference (RNAi) pathways , including the Piwi pathway; however, we have frequently observed newly thawed and stressed OSS and OSC cultures succumb after a few weeks of growth as cells lose adherence to the plastic substrate and lift off in clumps. "
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