Processing of Drosophila endo-siRNAs depends on a specific Loquacious isoform

作者：Zhou Rui; Czech Benjamin; Brennecke Julius; Sachidanandam Ravi; Wohlschlegel James A; Perrimon Norbert; Hannon Gregory J^*

来源：RNA-A Publication of the RNA Society, 2009, 15(10): 1886-1895.

DOI：10.1261/rna.1611309

• Drosophila melanogaster
• Dicer
• double-stranded RNA-binding proteins (dsRBPs)
• Loquacious
• endo-siRNA processing
• transposon silencing

Drosophila melanogaster expresses three classes of small RNAs, which are classified according to their mechanisms of biogenesis. MicroRNAs are similar to 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 similar to 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 similar to 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.

• 出版日期2009-10