Chan Simon W-L
Department of Plant Biology, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, USA.
Trends Plant Sci. 2008 Jul;13(7):383-9. doi: 10.1016/j.tplants.2008.05.001. Epub 2008 Jun 10.
Plant gene silencing is targeted to transposons and repeated sequences by small RNAs from the RNA interference (RNAi) pathway. Like classical RNAi, RNA-directed chromatin silencing involves the cleavage of double-stranded RNA by Dicer endonucleases to create small interfering RNAs (siRNAs), which bind to the Argonaute protein. The production of double-stranded RNA (dsRNA) must be carefully controlled to prevent inappropriate silencing. A plant-specific RNA polymerase IV (Pol IV) initiates siRNA production at silent heterochromatin, but Pol IV-independent mechanisms for making dsRNA also exist. Downstream of siRNA biogenesis, multiple chromatin marks might be targeted by Argonaute-siRNA complexes, yet mechanisms of chromatin modification remain poorly understood. Genomic studies of siRNA target loci promise to reveal novel biological functions for chromatin-targeted RNAi.
植物基因沉默通过RNA干扰（RNAi）途径产生的小RNA靶向转座子和重复序列。与经典RNAi一样，RNA指导的染色质沉默涉及Dicer核酸内切酶切割双链RNA以产生小干扰RNA（siRNA），这些小干扰RNA与Argonaute蛋白结合。双链RNA（dsRNA）的产生必须受到严格控制，以防止不适当的沉默。一种植物特异性RNA聚合酶IV（Pol IV）在沉默的异染色质处启动siRNA的产生，但也存在不依赖Pol IV产生dsRNA的机制。在siRNA生物合成的下游，Argonaute-siRNA复合物可能靶向多种染色质标记，但染色质修饰的机制仍知之甚少。对siRNA靶位点的基因组研究有望揭示染色质靶向RNAi的新生物学功能。
