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KMID : 0578320080260030308
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Molecules and Cells
2008 Volume.26 No. 3 p.308 ~ p.313
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Cleavage of the Star Strand Facilitates Assembly of Some MicroRNAs into Ago2-containing Silencing Complexes in Mammals
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Shin Chan-Seok
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Abstract
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In animals, microRNAs (miRNAs) and small interfering RNAs (siRNAs) repress expression of protein coding genes by assembling distinct RNA-induced silencing complexes (RISCs). It has previously been shown that passenger-strand cleavage is the predominant mechanism when siRNA duplexes are loaded into Argonaute2 (Ago2)-containing RISC, while an unwinding bypass mechanism is favored for miRNA duplexes with mismatches. Here I present experimental data indicating that some mammalian miRNAs are assembled into Ago2-containing RISC by cleaving their corresponding miRNA star strands. This phenomenon may depend on the secondary structure near the scissile phosphate of the miRNA duplex. In addition, I show that ATP is not required for star-strand cleavage in this process. Taken together, the data here provide insight into the miRNA-loading mechanisms in mammals.
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KEYWORD
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Argonaute, microRNA, miRNA star-strand cleavage, passenger-strand cleavage, RISC
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