title: Loqs and R2D2 act sequentially in the siRNA pathway in Drosophila.
abstract: In Drosophila melanogaster, the small interfering RNA (siRNA) pathway is triggered by exogenous double-stranded RNA (dsRNA) or upon viral infection. This pathway requires Dicer-2 (Dcr-2) in association with a dsRNA-binding protein (dsRBP) called R2D2. A potentially distinct siRNA pathway, which requires Dcr-2 in association with a different dsRBP, called Loquacious (Loqs), is activated by endogenous dsRNA derived from transposons, structured loci and overlapping transcripts. Here we show that different sources of dsRNA enter a common siRNA pathway that requires R2D2 and Loqs. R2D2 and loqs mutants show impaired silencing triggered by injection of exogenous dsRNA or by artificial and natural expression of endogenous dsRNA. In addition, we show that these dsRBPs function sequentially and nonredundantly in collaboration with Dcr-2. Loqs is primarily required for dsRNA processing, whereas R2D2 is essential for the subsequent loading of siRNAs into effector Ago-RISC complexes.
authors.affiliation: Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois, USA.
authors.forename: João Trindade
authors.initials: JT
authors.lastname: Marques
authors.forename: Kevin
authors.initials: K
authors.lastname: Kim
authors.forename: Pei-Hsuan
authors.initials: PH
authors.lastname: Wu
authors.forename: Trevis M
authors.initials: TM
authors.lastname: Alleyne
authors.forename: Nadereh
authors.initials: N
authors.lastname: Jafari
authors.forename: Richard W
authors.initials: RW
authors.lastname: Carthew
mesh_terms: D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000378:metabolism*; D035683:MicroRNAs / Q000096:biosynthesis; D008969:Molecular Sequence Data; D020365:RNA Helicases / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D034743:RNA-Induced Silencing Complex / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D043244:Ribonuclease III / Q000378:metabolism; D017422:Sequence Analysis, DNA
chemical_list: D029721:Drosophila Proteins; C503213:Loqs protein, Drosophila; D035683:MicroRNAs; C478068:R2D2 protein, Drosophila; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D034743:RNA-Induced Silencing Complex; C478069:DCR-2 protein, Drosophila; D043244:Ribonuclease III; D020365:RNA Helicases