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RNA helicase Belle/DDX3 regulates transgene expression in Drosophila
- Lo, Pang-Kuo, Huang, Yi-Chun, Poulton, John S., Leake, Nicholas, Palmer, William H., Vera, Daniel, Xie, Gengqiang, Klusza, Stephen, Deng, Wu-Min
- Developmental biology 2016 v.412 pp. 57-70
- DEAD-box RNA helicases, Drosophila, RNA interference, biogenesis, chromatin, female fertility, gene expression, germ cells, humans, microRNA, mutants, mutation, oogenesis, phenotype, small interfering RNA, transgenes, yeasts
- Belle (Bel), the Drosophila homolog of the yeast DEAD-box RNA helicase DED1 and human DDX3, has been shown to be required for oogenesis and female fertility. Here we report a novel role of Bel in regulating the expression of transgenes. Abrogation of Bel by mutations or RNAi induces silencing of a variety of P-element-derived transgenes. This silencing effect depends on downregulation of their RNA levels. Our genetic studies have revealed that the RNA helicase Spindle-E (Spn-E), a nuage RNA helicase that plays a crucial role in regulating RNA processing and PIWI-interacting RNA (piRNA) biogenesis in germline cells, is required for loss-of-bel-induced transgene silencing. Conversely, Bel abrogation alleviates the nuage-protein mislocalization phenotype in spn-E mutants, suggesting a competitive relationship between these two RNA helicases. Additionally, disruption of the chromatin remodeling factor Mod(mdg4) or the microRNA biogenesis enzyme Dicer-1 (Dcr-1) also alleviates the transgene-silencing phenotypes in bel mutants, suggesting the involvement of chromatin remodeling and microRNA biogenesis in loss-of-bel-induced transgene silencing. Finally we show that genetic inhibition of Bel function leads to de novo generation of piRNAs from the transgene region inserted in the genome, suggesting a potential piRNA-dependent mechanism that may mediate transgene silencing as Bel function is inhibited.