Essential and overlapping functions for mammalian Argonautes in microRNA silencing.
MicroRNA (miRNA) silencing fine-tunes protein output and regulates diverse biological processes. Argonaute (Ago) proteins are the core effectors of the miRNA pathway. In lower organisms, multiple Agos have evolved specialized functions for distinct RNA silencing pathways. However, the roles of mammalian Agos have not been well characterized. Here we show that mouse embryonic stem (ES) cells deficient for Ago1-4 are completely defective in miRNA silencing and undergo apoptosis. In miRNA silencing-defective ES cells, the proapoptotic protein Bim, a miRNA target, is increased, and up-regulation of Bim is sufficient to induce ES cell apoptosis. Expression of activated Akt inhibits Bim expression and partially rescues the growth defect in Ago-deficient ES cells. Furthermore, reintroduction of any single Ago into Ago-deficient cells is able to rescue the endogenous miRNA silencing defect and apoptosis. Consistent with this, each Ago is functionally equivalent with bulged miRNA duplexes for translational repression, whereas Ago1 and Ago2 appear to be more effective at utilizing perfectly matched siRNAs. Thus, our results demonstrate that mammalian Agos all contribute to miRNA silencing, and individual Agos have largely overlapping functions in this process.
Su
Hong
H
Department of Biochemistry, Northwestern University, Evanston, Illinois 60208, USA.
Trombly
Melanie I
MI
Chen
Jian
J
Wang
Xiaozhong
X
D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D000072224:Bcl-2-Like Protein 11; D002460:Cell Line; D002470:Cell Survival; D022202:Chromosomes, Artificial, Bacterial / Q000235:genetics; D053595:Embryonic Stem Cells / Q000166:cytology / Q000378:metabolism; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics* / Q000378:metabolism*; D018390:Gene Targeting; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics
D051017:Apoptosis Regulatory Proteins; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; D015852:Eukaryotic Initiation Factor-2; D008565:Membrane Proteins; D035683:MicroRNAs; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering