Argonaute2 Is the Catalytic Engine of Mammalian RNAi

  title={Argonaute2 Is the Catalytic Engine of Mammalian RNAi},
  author={Jidong Liu and Michelle A. Carmell and Fabiola V. Rivas and Carolyn G. Marsden and J. Michael Thomson and Ji-Joon Song and Scott M. Hammond and Leemor Joshua-Tor and Gregory J. Hannon},
  pages={1437 - 1441}
Gene silencing through RNA interference (RNAi) is carried out by RISC, the RNA-induced silencing complex. RISC contains two signature components, small interfering RNAs (siRNAs) and Argonaute family proteins. Here, we show that the multiple Argonaute proteins present in mammals are both biologically and biochemically distinct, with a single mammalian family member, Argonaute2, being responsible for messenger RNA cleavage activity. This protein is essential for mouse development, and cells… 

over-The Argonautes

  • Biology
  • 2007
Structural and biochemical studies on Argonaute identified this protein as Slicer, the enzyme in RISC that cleaves the mRNA as directed by the siRNA, the role of the Argonautes as S Alicers and non-Slicers is discussed.

Argonaute 2/RISC resides in sites of mammalian mRNA decay known as cytoplasmic bodies

It is shown that Argonaute 2, a key component of RISC, is not randomly distributed but concentrates in mRNA decay centres that are known as cytoplasmic bodies, providing new insight into the mechanism of RNAi function.

Artificial tethering of Argonaute proteins for studying their role in translational repression of target mRNAs.

To examine the exact role of the Argonaute protein in the silencing complex, human Argonautes were artificially recruited to reporter mRNAs in a small RNA-independent manner by the BoxB-N-peptide tethering system.

Purified Argonaute2 and an siRNA form recombinant human RISC

It is demonstrated that recombinant, human Argonaute2 can combine with a small interfering RNA (siRNA) to form minimal RISC that accurately cleaves substrate RNAs and provide a source of recombinant enzyme for detailed biochemical studies of the RNAi effector complex.

Eukaryotic Argonautes come into focus.

In vitro RNA cleavage assay for Argonaute-family proteins.

Slicer assays using endogenous and recombinant Argonaute protein produced in and purified from Escherichia coli are described, showing full complementarity between the small RNA and its target messenger RNA results in RISC-mediated cleavage ("Slicing") of the target mRNA.

Argonautes confront new small RNAs.

Bacterial Expression of Mouse Argonaute 2 for Functional and Mutational Studies

expression in E. coli of mouse Ago2 and testing of its enzymatic activity in a RISC assay show that the enzyme can load the siRNA and cleave the complementary RNA in absence of other cellular factors, as described for human Ago2.

Proteomics Identification of Drosophila Small Interfering RNA-associated Factors*

This study identified both established RISC components and novel siRNA-associated factors, many of which contain domains that are consistent with potential roles in RNAi.

Mechanism of RNA interference ( RNAi ) : Current concept

RNAi is an evolutionary conserved silencing pathway in which the double stranded RNA is broken down into small interfering RNA (siRNA) with the help of dicer and RNA-induced silencing complex (RISC)



Distinct roles for Argonaute proteins in small RNA-directed RNA cleavage pathways.

It is shown that AGO2 is an essential component for siRNA-directed RNA interference (RNAi) response and is required for the unwinding of siRNA duplex and in consequence assembly of si RNA into RISC in Drosophila embryos, and that distinct Argonaute proteins act at different steps of the small RNA silencing mechanism.

Argonaute2, a Link Between Genetic and Biochemical Analyses of RNAi

Biochemical purification of the RNAi effector nuclease from cultured Drosophila cells reveals that one constituent of this complex is a member of the Argonaute family of proteins, which are essential for gene silencing in Caenorhabditis elegans, Neurospora, and Arabidopsis.

Fragile X-related protein and VIG associate with the RNA interference machinery.

The characterization of RNAi effector complexes (RISCs) that contain small interfering RNAs and microRNAs (miRNAs) and the possibility that dFXR, and potentially FMRP, use, at least in part, an RNAi-related mechanism for target recognition suggests a potentially important link between RNAi and human disease.

Role for a bidentate ribonuclease in the initiation step of RNA interference

Dicer is a member of the RNase III family of nucleases that specifically cleave double-stranded RNAs, and is evolutionarily conserved in worms, flies, plants, fungi and mammals, and has a distinctive structure, which includes a helicase domain and dualRNase III motifs.

A microRNA in a Multiple-Turnover RNAi Enzyme Complex

It is shown that, in human cell extracts, the miRNA let-7 naturally enters the RNAi pathway, which suggests that only the degree of complementarity between a miRNA and its RNA target determines its function.

Crystal Structure of Argonaute and Its Implications for RISC Slicer Activity

The architecture of the molecule and the placement of the PAZ and PIWI domains define a groove for substrate binding and suggest a mechanism for siRNA-guided mRNA cleavage.

siRNAs can function as miRNAs.

It is shown that a short interfering RNA (siRNA) can repress expression of a target mRNA with partially complementary binding sites in its 3' UTR, much like the demonstrated function of endogenously encoded microRNAs (miRNAs).

The Argonaute family: tentacles that reach into RNAi, developmental control, stem cell maintenance, and tumorigenesis.

Argonaute proteins comprise a highly conserved protein family that is involved in a variety of RNA silencing phenomena in a diverse set of organisms and may ultimately reveal the reach of these pathways into the basic biological mechanisms that underlie a range of human diseases.