Dual Role for Argonautes in MicroRNA Processing and Posttranscriptional Regulation of MicroRNA Expression

Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA.
Cell (Impact Factor: 32.24). 01/2008; 131(6):1097-108. DOI: 10.1016/j.cell.2007.10.032
Source: PubMed


MicroRNAs are small endogenous noncoding RNAs involved in posttranscriptional gene regulation. During microRNA biogenesis, Drosha and Dicer process the primary transcript (pri-miRNA) through a precursor hairpin (pre-miRNA) to the mature miRNA. The miRNA is incorporated into the RNA-Induced Silencing Complex (RISC) with Argonaute proteins, the effector molecules in RNA interference (RNAi). Here, we show that all Argonautes elevate mature miRNA expression posttranscriptionally, independent of RNase activity. Also, we identify a role for the RISC slicer Argonaute2 (Ago2) in cleaving the pre-miRNA to an additional processing intermediate, termed Ago2-cleaved precursor miRNA or ac-pre-miRNA. This endogenous, on-pathway intermediate results from cleavage of the pre-miRNA hairpin 12 nucleotides from its 3'-end. By analogy to siRNA processing, Ago2 cleavage may facilitate removal of the nicked passenger strand from RISC after maturation. The multiple roles of Argonautes in the RNAi effector phase and miRNA biogenesis and maturation suggest coordinate regulation of microRNA expression and function.

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Available from: Sven Diederichs, Jan 09, 2014
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    • "MicroRNAs abundance is dependent on the presence of Argonaute proteins. It has been previously reported that a loss of Ago2 resulted in loss of microRNA and the reexpression of Argonaute proteins led to increased expression of precursor microRNAs [8]. However, the mechanisms that regulate microRNAs turnover are not fully understood neither perhaps fully identified. "
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    ABSTRACT: MicroRNAs are endogenous regulators of gene expression either by inhibiting translation or protein degradation. Recent studies indicate that microRNAs play a role in cardiovascular disease and renin-angiotensin-aldosterone system- (RAAS-) mediated cardiovascular inflammation, either as mediators or being targeted by RAAS pharmacological inhibitors. The exact role(s) of microRNAs in RAAS-mediated cardiovascular inflammation and remodeling is/are still in early stage of investigation. However, few microRNAs have been shown to play a role in RAAS signaling, particularly miR-155, miR-146a/b, miR-132/122, and miR-483-3p. Identification of specific microRNAs and their targets and elucidating microRNA-regulated mechanisms associated RAS-mediated cardiovascular inflammation and remodeling might lead to the development of novel pharmacological strategies to target RAAS-mediated vascular pathologies. This paper reviews microRNAs role in inflammatory factors mediating cardiovascular inflammation and RAAS genes and the effect of RAAS pharmacological inhibition on microRNAs and the resolution of RAAS-mediated cardiovascular inflammation and remodeling. Also, this paper discusses the advances on microRNAs-based therapeutic approaches that may be important in targeting RAAS signaling.
    06/2015; 2015:1-7. DOI:10.1155/2015/101527
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    • "Ago2 contributes to the production of truncated species by cleaving pre-miRNAs in the middle of the 3 0 strand. This results in truncated hairpins called Ago-cleaved pre-miRNAs (ac-pre-miRNAs) (Diederichs & Haber, 2007). There is little evidence that ac-pre-miRNAs generate mature miRNAs with an exception of ac-pre-miR-451 that is shorter than others and trimmed further into mature miRNA (Cheloufi et al, 2010; Cifuentes et al, 2010; Yang et al, 2010; Yoda et al, 2013). "
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    ABSTRACT: Terminal uridylyl transferases (TUTs) function as integral regulators of microRNA (miRNA) biogenesis. Using biochemistry, single-molecule, and deep sequencing techniques, we here investigate the mechanism by which human TUT7 (also known as ZCCHC6) recognizes and uridylates precursor miRNAs (pre-miRNAs) in the absence of Lin28. We find that the overhang of a pre-miRNA is the key structural element that is recognized by TUT7 and its paralogues, TUT4 (ZCCHC11) and TUT2 (GLD2/PAPD4). For group II pre-miRNAs, which have a 1-nt 3′ overhang, TUT7 restores the canonical end structure (2-nt 3′ overhang) through mono-uridylation, thereby promoting miRNA biogenesis. For pre-miRNAs where the 3′ end is further recessed into the stem (as in 3′ trimmed pre-miRNAs), TUT7 generates an oligo-U tail that leads to degradation. In contrast to Lin28-stimulated oligo-uridylation, which is processive, a distributive mode is employed by TUT7 for both mono- and oligo-uridylation in the absence of Lin28. The overhang length dictates the frequency (but not duration) of the TUT7-RNA interaction, thus explaining how TUT7 differentiates pre-miRNA species with different overhangs. Our study reveals dual roles and mechanisms of uridylation in repair and removal of defective pre-miRNAs.
    The EMBO Journal 05/2015; 34(13). DOI:10.15252/embj.201590931 · 10.43 Impact Factor
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    • "In the context of interferon-induced PKR activation, it has been proposed that TRBP inhibits PKR function both by dsRNA sequestration and by direct protein-protein interaction (Benkirane et al., 1997; Park et al., 1994). In contrast, we describe above that metabolic stress induces interaction between TRBP and PKR, leading to PKR activation and suggesting a dual regulatory role for TRBP, as has been reported for some other components of the RLC (Clerzius et al., 2013; Diederichs and Haber, 2007). In an attempt to gain mechanistic insights into TRBP function, we asked whether a post-translational modification of TRBP might alter its interaction with PKR and differentially regulate its activity . "
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    ABSTRACT: Aberrant stress and inflammatory responses are key factors in the pathogenesis of obesity and metabolic dysfunction, and the double-stranded RNA-dependent kinase (PKR) has been proposed to play an important role in integrating these pathways. Here, we report the formation of a complex between PKR and TAR RNA-binding protein (TRBP) during metabolic and obesity-induced stress, which is critical for the regulation of eukaryotic translation initiation factor 2 alpha (eIF2α) phosphorylation and c-Jun N-terminal kinase (JNK) activation. We show that TRBP phosphorylation is induced in the setting of metabolic stress, leading to PKR activation. Suppression of hepatic TRBP reduced inflammation, JNK activity, and eIF2α phosphorylation and improved systemic insulin resistance and glucose metabolism, while TRBP overexpression exacerbated the impairment in glucose homeostasis in obese mice. These data indicate that the association between PKR and TRBP integrates metabolism with translational control and inflammatory signaling and plays important roles in metabolic homeostasis and disease. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
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