Zhou Rui, Czech Benjamin, Brennecke Julius, Sachidanandam Ravi, Wohlschlegel James A, Perrimon Norbert, Hannon Gregory J
Harvard Medical School, Department of Genetics, Howard Hughes Medical Institute, Boston, Massachusetts 02115, USA.
RNA. 2009 Oct;15(10):1886-95. doi: 10.1261/rna.1611309. Epub 2009 Jul 27.
Drosophila melanogaster expresses three classes of small RNAs, which are classified according to their mechanisms of biogenesis. MicroRNAs are approximately 22-23 nucleotides (nt), ubiquitously expressed small RNAs that are sequentially processed from hairpin-like precursors by Drosha/Pasha and Dcr-1/Loquacious complexes. MicroRNAs usually associate with AGO1 and regulate the expression of protein-coding genes. Piwi-interacting RNAs (piRNAs) of approximately 24-28 nt associate with Piwi-family proteins and can arise from single-stranded precursors. piRNAs function in transposon silencing and are mainly restricted to gonadal tissues. Endo-siRNAs are found in both germline and somatic tissues. These approximately 21-nt RNAs are produced by a distinct Dicer, Dcr-2, and do not depend on Drosha/Pasha complexes. They predominantly bind to AGO2 and target both mobile elements and protein-coding genes. Surprisingly, a subset of endo-siRNAs strongly depend for their production on the dsRNA-binding protein Loquacious (Loqs), thought generally to be a partner for Dcr-1 and a cofactor for miRNA biogenesis. Endo-siRNA production depends on a specific Loqs isoform, Loqs-PD, which is distinct from the one, Loqs-PB, required for the production of microRNAs. Paralleling their roles in the biogenesis of distinct small RNA classes, Loqs-PD and Loqs-PB bind to different Dicer proteins, with Dcr-1/Loqs-PB complexes and Dcr-2/Loqs-PD complexes driving microRNA and endo-siRNA biogenesis, respectively.
黑腹果蝇表达三类小RNA，它们根据生物合成机制进行分类。微小RNA约为22 - 23个核苷酸（nt），是普遍表达的小RNA，通过Drosha/Pasha和Dcr - 1/Loquacious复合物从发夹状前体依次加工而成。微小RNA通常与AGO1结合并调节蛋白质编码基因的表达。约24 - 28 nt的Piwi相互作用RNA（piRNA）与Piwi家族蛋白结合，可源自单链前体。piRNA在转座子沉默中起作用，主要局限于性腺组织。内源性小干扰RNA（endo - siRNA）存在于生殖系和体细胞组织中。这些约21 nt的RNA由一种独特的Dicer即Dcr - 2产生，且不依赖于Drosha/Pasha复合物。它们主要与AGO2结合，并靶向移动元件和蛋白质编码基因。令人惊讶的是，一部分endo - siRNA的产生强烈依赖于双链RNA结合蛋白Loquacious（Loqs），通常认为它是Dcr - 1的伙伴和微小RNA生物合成的辅助因子。Endo - siRNA的产生依赖于一种特定的Loqs异构体Loqs - PD，它与微小RNA产生所需的Loqs - PB不同。与它们在不同小RNA类别的生物合成中的作用相似，Loqs - PD和Loqs - PB与不同的Dicer蛋白结合，Dcr - 1/Loqs - PB复合物和Dcr - 2/Loqs - PD复合物分别驱动微小RNA和endo - siRNA的生物合成。
