title: RNA helicase Belle/DDX3 regulates transgene expression in Drosophila.
abstract: 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.
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL, USA.
authors.forename: Pang-Kuo
authors.initials: PK
authors.lastname: Lo
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL, USA.
authors.forename: Yi-Chun
authors.initials: YC
authors.lastname: Huang
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL, USA.
authors.forename: John S
authors.initials: JS
authors.lastname: Poulton
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL, USA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Leake
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL, USA.
authors.forename: William H
authors.initials: WH
authors.lastname: Palmer
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Vera
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL, USA.
authors.forename: Gengqiang
authors.initials: G
authors.lastname: Xie
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL, USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Klusza
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL, USA. Electronic address: wumin@bio.fsu.edu.
authors.forename: Wu-Min
authors.initials: WM
authors.lastname: Deng
mesh_terms: D000818:Animals; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics*; D020868:Gene Silencing; D009154:Mutation; D020365:RNA Helicases / Q000235:genetics*; D019076:Transgenes
chemical_list: D029721:Drosophila Proteins; C558829:Bel protein, Drosophila; D020365:RNA Helicases
keywords: Belle; Dcr-1; Mod(mdg4); Spindle-E; Transgene silencing; miRNA; piRNAs