Yoshikawa Manabu
Division of Plant Sciences, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki 305-8602, Japan.
Genes Genet Syst. 2013;88(2):77-84. doi: 10.1266/ggs.88.77.
Trans-acting small interfering RNAs (tasiRNAs) are plant-specific endogenous siRNAs that control non-identical mRNAs via cleavage. The production of tasiRNAs is triggered by cleavage of capped and polyadenylated primary TAS transcripts (pri-TASs) by specific miRNAs. Following miRNA-directed cleavage, either 5' or 3' cleavage fragments are converted into double-stranded RNAs (dsRNAs) by RNA-DEPENDENT RNA POLYMERASE 6. The dsRNAs are processed to tasiRNAs by DICER-LIKE 4 in a phasing manner. There are two forms of pri-TASs; One has a single miRNA target site that is targeted by 22-nucleotide microRNAs, and the other has two miR390 target sites. Secondary siRNAs that are important for the amplification of RNA silencing are defined as siRNAs whose production is initiated by the cleavage of primary small RNA-containing RNA-induced silencing complexes. Thus, tasiRNA production is a model system of secondary siRNA production in plants. This review focuses on the production of tasiRNAs that are endogenous secondary siRNAs.
反式作用小干扰RNA（tasiRNA）是植物特有的内源性小干扰RNA，通过切割作用调控不同的mRNA。tasiRNA的产生由特定miRNA对带帽和多聚腺苷酸化的初级TAS转录本（pri-TAS）进行切割所触发。在miRNA介导的切割之后，5'或3'切割片段通过RNA依赖的RNA聚合酶6转化为双链RNA（dsRNA）。dsRNA由类Dicer 4以相位方式加工成tasiRNA。pri-TAS有两种形式；一种具有单个miRNA靶位点，可被22个核苷酸的微小RNA靶向，另一种具有两个miR390靶位点。对RNA沉默扩增很重要的二级小干扰RNA被定义为其产生由含初级小RNA的RNA诱导沉默复合体的切割所启动的小干扰RNA。因此，tasiRNA的产生是植物中二级小干扰RNA产生的一个模型系统。本综述聚焦于作为内源性二级小干扰RNA的tasiRNA的产生。
