Erhard Karl F, Stonaker Jennifer L, Parkinson Susan E, Lim Jana P, Hale Christopher J, Hollick Jay B
Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, CA 94720-3102, USA.
Science. 2009 Feb 27;323(5918):1201-5. doi: 10.1126/science.1164508.
Plants have distinct RNA polymerase complexes (Pol IV and Pol V) with largely unknown roles in maintaining small RNA-associated gene silencing. Curiously, the eudicot Arabidopsis thaliana is not affected when either function is lost. By use of mutation selection and positional cloning, we showed that the largest subunit of the presumed maize Pol IV is involved in paramutation, an inherited epigenetic change facilitated by an interaction between two alleles, as well as normal maize development. Bioinformatics analyses and nuclear run-on transcription assays indicate that Pol IV does not engage in the efficient RNA synthesis typical of the three major eukaryotic DNA-dependent RNA polymerases. These results indicate that Pol IV employs abnormal RNA polymerase activities to achieve genome-wide silencing and that its absence affects both maize development and heritable epigenetic changes.
植物具有独特的RNA聚合酶复合物（Pol IV和Pol V），它们在维持与小RNA相关的基因沉默方面的作用很大程度上未知。奇怪的是，当这两种功能丧失时，双子叶植物拟南芥不受影响。通过突变筛选和定位克隆，我们表明推测的玉米Pol IV的最大亚基参与了副突变，这是一种由两个等位基因之间的相互作用促进的遗传表观遗传变化，以及正常的玉米发育。生物信息学分析和核运行转录分析表明，Pol IV不参与三种主要真核生物DNA依赖性RNA聚合酶典型的高效RNA合成。这些结果表明，Pol IV利用异常的RNA聚合酶活性来实现全基因组沉默，并且它的缺失会影响玉米发育和可遗传的表观遗传变化。
