Dicer-2 and R2D2 coordinately bind siRNA to promote assembly of the siRISC complexes

Xiang Liu; Feng Jiang; Savitha Kalidas; Dean Smith; Qinghua Liu

doi:10.1261/rna.101606

Dicer-2 and R2D2 coordinately bind siRNA to promote assembly of the siRISC complexes

¹Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
²Department of Pharmacology and Center for Basic Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA

Abstract

In Drosophila melanogaster, the Dicer-2/R2D2 complex initiates RNA interference (RNAi) by processing long double-stranded RNA (dsRNA) into small interfering RNA (siRNA). Recent biochemical studies suggest that the Dcr-2/R2D2 complex also facilitates incorporation of siRNA into the RNA-induced silencing complex (siRISC). Here we present genetic evidence that R2D2 and Dcr-2 are both required for loading siRNA onto the siRISC complex. Consistent with this, only the Dcr-2/R2D2 complex, but neither Dcr-2 nor R2D2 alone, can efficiently interact with duplex siRNA. Furthermore, both dsRNA-binding domains of R2D2 are critical for binding to siRNA and promoting assembly of the siRISC complexes.

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Footnotes

Reprint requests to: Qinghua Liu, Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; e-mail: qliu{at}biochem.swmed.edu; fax: (214) 648-9729.
Article published online ahead of print. Article and publication date are at http://www.rnajournal.org/cgi/doi/10.1261/rna.101606.
- Received March 30, 2006.
- Accepted May 4, 2006.