A micrococcal nuclease homologue in RNAi effector complexes.

Amy A Caudy, René F Ketting, Scott M Hammond, Ahmet M Denli, Anja M P Bathoorn, Bastiaan B J Tops, Jose M Silva, Mike M Myers, Gregory J Hannon, Ronald H A Plasterk

Cold Spring Harbor Laboratory, Watson School of Biological Sciences, 1 Bungtown Road, Cold Spring Harbor, New York 11724, USA.

Nature 2003 Sep 25

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RNA interference (RNAi) regulates gene expression by the cleavage of messenger RNA, by mRNA degradation and by preventing protein synthesis. These effects are mediated by a ribonucleoprotein complex known as RISC (RNA-induced silencing complex). We have previously identified four Drosophila components (short interfering RNAs, Argonaute 2 (ref. 2), VIG and FXR) of a RISC enzyme that degrades specific mRNAs in response to a double-stranded-RNA trigger. Here we show that Tudor-SN (tudor staphylococcal nuclease)--a protein containing five staphylococcal/micrococcal nuclease domains and a tudor domain--is a component of the RISC enzyme in Caenorhabditis elegans, Drosophila and mammals. Although Tudor-SN contains non-canonical active-site sequences, we show that purified Tudor-SN exhibits nuclease activity similar to that of other staphylococcal nucleases. Notably, both purified Tudor-SN and RISC are inhibited by a specific competitive inhibitor of micrococcal nuclease. Tudor-SN is the first RISC subunit to be identified that contains a recognizable nuclease domain, and could therefore contribute to the RNA degradation observed in RNAi.

Citation

Amy A Caudy, René F Ketting, Scott M Hammond, Ahmet M Denli, Anja M P Bathoorn, Bastiaan B J Tops, Jose M Silva, Mike M Myers, Gregory J Hannon, Ronald H A Plasterk. A micrococcal nuclease homologue in RNAi effector complexes. Nature. 2003 Sep 25;425(6956):411-4