Cleavage of the star strand facilitates assembly of some microRNAs into Ago2-containing silencing complexes in mammals.
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.
Shin
Chanseok
C
The Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, USA. cshin@wi.mit.edu
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D060565:Argonaute Proteins; D001483:Base Sequence; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism*; D020868:Gene Silencing; D006801:Humans; D035683:MicroRNAs / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D034741:RNA, Small Interfering / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D034743:RNA-Induced Silencing Complex / Q000235:genetics / Q000378:metabolism*
C466422:AGO2 protein, human; D060565:Argonaute Proteins; D015852:Eukaryotic Initiation Factor-2; D035683:MicroRNAs; D034741:RNA, Small Interfering; D034743:RNA-Induced Silencing Complex; D000255:Adenosine Triphosphate