A Link Between mRNA Turnover and RNA Interference in Arabidopsis

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Science  05 Nov 2004:
Vol. 306, Issue 5698, pp. 1046-1048
DOI: 10.1126/science.1101092

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In RNA interference (RNAi), double-stranded RNA (dsRNA) triggers degradation of homologous messenger RNA. In many organisms, RNA-dependent RNA polymerase (RdRp) is required to initiate or amplify RNAi, but the substrate for dsRNA synthesis in vivo is not known. Here, we show that RdRp-dependent transgene silencing in Arabidopsis was caused by mutation of XRN4, which is a ribonuclease (RNase) implicated in mRNA turnover by means of decapping and 5′-3′ exonucleolysis. When both XRN4 and the RdRp were mutated, the plants accumulated decapped transgene mRNA. We propose that mRNAs lacking a cap structure become exposed to RdRp to initiate or maintain RNAi.

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