title: Evidence that siRNAs function as guides, not primers, in the Drosophila and human RNAi pathways.
abstract: In Drosophila, two features of small interfering RNA (siRNA) structure--5' phosphates and 3' hydroxyls--are reported to be essential for RNA interference (RNAi). Here, we show that as in Drosophila, a 5' phosphate is required for siRNA function in human HeLa cells. In contrast, we find no evidence in flies or humans for a role in RNAi for the siRNA 3' hydroxyl group. Our in vitro data suggest that in both flies and mammals, each siRNA guides endonucleolytic cleavage of the target RNA at a single site. We conclude that the underlying mechanism of RNAi is conserved between flies and mammals and that RNA-dependent RNA polymerases are not required for RNAi in these organisms.
authors.affiliation: Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
authors.forename: Dianne S
authors.initials: DS
authors.lastname: Schwarz
authors.forename: György
authors.initials: G
authors.lastname: Hutvágner
authors.forename: Benjamin
authors.initials: B
authors.lastname: Haley
authors.forename: Phillip D
authors.initials: PD
authors.lastname: Zamore
mesh_terms: D000818:Animals; D004331:Drosophila melanogaster / Q000196:embryology / Q000235:genetics*; D004722:Endoribonucleases / Q000378:metabolism; D005786:Gene Expression Regulation; D017344:Genes, Insect; D006367:HeLa Cells; D006801:Humans; D010710:Phosphates / Q000378:metabolism; D034622:RNA Interference / Q000502:physiology*; D012330:RNA, Double-Stranded / Q000737:chemistry / Q000378:metabolism; D034741:RNA, Small Interfering / Q000737:chemistry / Q000378:metabolism*; D043244:Ribonuclease III
chemical_list: D010710:Phosphates; D012330:RNA, Double-Stranded; D034741:RNA, Small Interfering; D004722:Endoribonucleases; D043244:Ribonuclease III