Dalmay T, Horsefield R, Braunstein T H, Baulcombe D C
The Sainsbury Laboratory, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK.
EMBO J. 2001 Apr 17;20(8):2069-78. doi: 10.1093/emboj/20.8.2069.
Post-transcriptional gene silencing (PTGS) provides protection in plants against virus infection and can suppress expression of transgenes. Arabidopsis plants carrying mutations at the SDE3 locus are defective in PTGS mediated by a green fluorescent protein transgene. However, PTGS mediated by tobacco rattle virus (TRV) was not affected by sde3. From these results we conclude that SDE3, like the previously described RNA polymerase encoded by SDE1, acts at a stage in the mechanism that is circumvented when PTGS is mediated by TRV. The product of SDE3 is similar to RNA helicase-like proteins including GB110 in mouse and other proteins in Drosophila and humans. These proteins are similar to, but clearly distinct from Upf1p and SMG-2, which are required for nonsense-mediated mRNA decay in yeast and Caenorhabditis elegans and, in the case of SMG-2, for PTGS.
转录后基因沉默（PTGS）为植物提供了抵御病毒感染的保护作用，并且能够抑制转基因的表达。在SDE3基因座携带突变的拟南芥植株在由绿色荧光蛋白转基因介导的PTGS中存在缺陷。然而，由烟草脆裂病毒（TRV）介导的PTGS不受sde3的影响。从这些结果我们得出结论，SDE3与先前描述的由SDE1编码的RNA聚合酶一样，在由TRV介导PTGS时所规避的机制阶段发挥作用。SDE3的产物与RNA解旋酶样蛋白相似，包括小鼠中的GB110以及果蝇和人类中的其他蛋白。这些蛋白与Upf1p和SMG-2相似，但明显不同，Upf1p和SMG-2是酵母和秀丽隐杆线虫中无义介导的mRNA降解所必需的，就SMG-2而言，是PTGS所必需的。
