Asymmetry of intronic pre-miRNA structures in functional RISC assembly

• Published in: Gene 2005-08, Vol.356, p.32-38
• Main Authors: Lin, Shi-Lung, Chang, Donald, Ying, Shao-Yao
• Format: Article
• Language: English
• Subjects: Animals; Base Sequence; Blotting, Northern; Blotting, Western; Danio rerio; Genetic Vectors - genetics; Green Fluorescent Proteins - genetics; Green Fluorescent Proteins - metabolism; intron; Introns - genetics; microRNA (miRNA); MicroRNAs - chemistry; MicroRNAs - genetics; MicroRNAs - metabolism; Nucleic Acid Conformation; RNA Interference; RNA interference (RNAi); RNA Precursors - chemistry; RNA Precursors - genetics; RNA Splicing; RNA, Messenger - genetics; RNA, Messenger - metabolism; RNA-induced gene silencing complex (RISC); RNA-Induced Silencing Complex - chemistry; RNA-Induced Silencing Complex - genetics; Transfection; Zebrafish
• ISSN: 0378-1119; 1879-0038
• DOI: 10.1016/j.gene.2005.04.036

The two oligonucleotide strands of a siRNA duplex are functionally asymmetric in assembling the RNAi effector, RNA-induced gene silencing complex (RISC). Based on this asymmetric RISC assembly model in vitro, formation of a microRNA (miRNA) and complementary miRNA (miRNA*) duplex was proposed to be an essential step for the assembly of miRNA-associated RISC (miRISC). We observed here that a strong structural bias exists in the selection of a mature miRNA strand for RISC assembly in zebrafish using an intronic miRNA-like vector to target EGFP mRNA for regulation. The position of the stemloop in a precursor miRNA (pre-miRNA) was involved in the determination of miRNA–miRNA* asymmetry of the pre-miRNA stemarm, leading to different miRNA maturation during miRISC assembly. These findings suggest that the miRISC assembly is likely different from the RISC assembly model of siRNA in zebrafish, providing the first in vivo evidence for asymmetric miRISC assembly.