A protein sensor for siRNA asymmetry
Graduate School of Biomedical Sciences; Department of Biochemistry and Molecular Pharmacology
Life Sciences | Medicine and Health Sciences
To act as guides in the RNA interference (RNAi) pathway, small interfering RNAs (siRNAs) must be unwound into their component strands, then assembled with proteins to form the RNA-induced silencing complex (RISC), which catalyzes target messenger RNA cleavage. Thermodynamic differences in the base-pairing stabilities of the 5' ends of the two approximately 21-nucleotide siRNA strands determine which siRNA strand is assembled into the RISC. We show that in Drosophila, the orientation of the Dicer-2/R2D2 protein heterodimer on the siRNA duplex determines which siRNA strand associates with the core RISC protein Argonaute 2. R2D2 binds the siRNA end with the greatest double-stranded character, thereby orienting the heterodimer on the siRNA duplex. Strong R2D2 binding requires a 5'-phosphate on the siRNA strand that is excluded from the RISC. Thus, R2D2 is both a protein sensor for siRNA thermodynamic asymmetry and a licensing factor for entry of authentic siRNAs into the RNAi pathway.
DOI of Published Version
Science. 2004 Nov 19;306(5700):1377-80. Link to article on publisher's site
Science (New York, N.Y.)
Tomari, Yukihide; Matranga, Christian B.; Haley, Benjamin; Martinez, Natalia Julia; and Zamore, Phillip D., "A protein sensor for siRNA asymmetry" (2004). GSBS Student Publications. 1256.