Dicer

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One molecule of the Dicer protein from Giardia intestinalis, which catalyzes the cleavage of dsRNA to siRNAs. The RNase III domains are colored green, the PAZ domain yellow, the platform domain red, and the connector helix blue. The distance between the RNase III and PAZ domains, determined by the length and angle of the connector helix, has been suggested as the determinant for the length of siRNA molecules produced by a given Dicer variant.^[1]

Dicer is an RNAse III ribonuclease that cleaves double-stranded RNA (dsRNA) and pre-microRNA (miRNA) into short double-stranded RNA fragments called small interfering RNA (siRNA) about 20-25 nucleotides long, usually with a two-base overhang on the 3' end. Dicer contains two RNase III domains and one PAZ domain; the distance between these two regions of the molecule is determined by the length and angle of the connector helix and determines the length of the siRNAs it produces.^[1] Dicer catalyzes the first step in the RNA interference pathway and initiates formation of the RNA-induced silencing complex (RISC), whose catalytic component argonaute is an endonuclease capable of degrading messenger RNA (mRNA) whose sequence is complementary to that of the siRNA guide strand.

Dicer was named by Emily Bernstein, a graduate student in Greg Hannon's group at the Cold Spring Harbor Laboratory, who first demonstrated its dsRNA "dicing" activity.

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[edit] References

1. ^ ^{a b} Macrae IJ, Zhou K, Li F, Repic A, Brooks AN, Cande WZ, Adams PD, Doudna JA. (2006). Structural basis for double-stranded RNA processing by Dicer. Science 311(5758):195-8.