title: A structural basis for discriminating between self and nonself double-stranded RNAs in mammalian cells.
abstract: Nonspecific effects triggered by small interfering RNAs (siRNAs) complicate the use of RNA interference (RNAi) to specifically downregulate gene expression. To uncover the basis of these nonspecific activities, we analyzed the effect of chemically synthesized siRNAs on mammalian double-stranded RNA (dsRNA)-activated signaling pathways. siRNAs ranging from 21 to 27 nucleotides (nt) in length activated the interferon system when they lacked 2-nt 3' overhangs, a characteristic of Dicer products. We show that the recognition of siRNAs is mediated by the RNA helicase RIG-I and that the presence of 3' overhangs impairs its ability to unwind the dsRNA substrate and activate downstream signaling to the transcription factor IRF-3. These results suggest a structural basis for discrimination between microRNAs that are endogenous Dicer products, and nonself dsRNAs such as by-products of viral replication. These findings will enable the rational design of siRNAs that avoid nonspecific effects or, alternatively, that induce bystander effects to potentially increase the efficacy of siRNA-based treatments of viral infections or cancer.
authors.affiliation: Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
authors.forename: Joao Trindade
authors.initials: JT
authors.lastname: Marques
authors.forename: Thalie
authors.initials: T
authors.lastname: Devosse
authors.forename: Die
authors.initials: D
authors.lastname: Wang
authors.forename: Maryam
authors.initials: M
authors.lastname: Zamanian-Daryoush
authors.forename: Paul
authors.initials: P
authors.lastname: Serbinowski
authors.forename: Rune
authors.initials: R
authors.lastname: Hartmann
authors.forename: Takashi
authors.initials: T
authors.lastname: Fujita
authors.forename: Mark A
authors.initials: MA
authors.lastname: Behlke
authors.forename: Bryan R G
authors.initials: BR
authors.lastname: Williams
mesh_terms: D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D015536:Down-Regulation; D005786:Gene Expression Regulation; D005821:Genetic Techniques; D006801:Humans; D050838:Interferon Regulatory Factor-3 / Q000235:genetics; D050356:Lipid Metabolism; D008957:Models, Genetic; D009369:Neoplasms / Q000378:metabolism; D034622:RNA Interference; D012330:RNA, Double-Stranded / Q000737:chemistry*; D034741:RNA, Small Interfering / Q000378:metabolism
chemical_list: D050838:Interferon Regulatory Factor-3; D012330:RNA, Double-Stranded; D034741:RNA, Small Interfering