Yu Bin, Bi Liu, Zhai Jixian, Agarwal Manu, Li Shengben, Wu Qingfa, Ding Shou-Wei, Meyers Blake C, Vaucheret Hervé, Chen Xuemei
Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California, Riverside, CA 92521, USA.
Nucleic Acids Res. 2010 Sep;38(17):5844-50. doi: 10.1093/nar/gkq348. Epub 2010 May 6.
Plant microRNAs (miRNAs) and small interfering RNAs (siRNAs) bear a 2'-O-methyl group on the 3'-terminal nucleotide. This methyl group is post-synthetically added by the methyltransferase protein HEN1 and protects small RNAs from enzymatic activities that target the 3'-OH. A mutagenesis screen for suppressors of the partial loss-of-function hen1-2 allele in Arabidopsis identified second-site mutations that restore miRNA methylation. These mutations affect two subunits of the DNA-dependent RNA polymerase IV (Pol IV), which is essential for the biogenesis of 24 nt endogenous siRNAs. A mutation in RNA-dependent RNA polymerase 2, another essential gene for the biogenesis of endogenous 24-nt siRNAs, also rescued the defects in miRNA methylation of hen1-2, revealing a previously unsuspected, negative influence of siRNAs on HEN1-mediated miRNA methylation. In addition, our findings imply the existence of a negative modifier of HEN1 activity in the Columbia genetic background.
植物微小RNA（miRNA）和小干扰RNA（siRNA）在3'末端核苷酸上带有一个2'-O-甲基基团。这个甲基基团是由甲基转移酶蛋白HEN1在合成后添加的，可保护小RNA免受靶向3'-OH的酶活性的影响。对拟南芥中部分功能丧失的hen1-2等位基因的抑制子进行诱变筛选，鉴定出了能恢复miRNA甲基化的第二位点突变。这些突变影响了DNA依赖性RNA聚合酶IV（Pol IV）的两个亚基，而Pol IV对于24 nt内源性siRNA的生物合成至关重要。RNA依赖性RNA聚合酶2（另一个对内源性24-nt siRNA生物合成至关重要的基因）中的一个突变也挽救了hen1-2的miRNA甲基化缺陷，揭示了siRNA对HEN1介导的miRNA甲基化以前未被怀疑的负面影响。此外，我们的研究结果表明在哥伦比亚遗传背景中存在HEN1活性的负调节因子。
