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XB-ART-51913
Mol Cell 2016 Mar 03;615:760-773. doi: 10.1016/j.molcel.2016.02.013.
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A Specialized Mechanism of Translation Mediated by FXR1a-Associated MicroRNP in Cellular Quiescence.

Bukhari SIA, Truesdell SS, Lee S, Kollu S, Classon A, Boukhali M, Jain E, Mortensen RD, Yanagiya A, Sadreyev RI, Haas W, Vasudevan S.


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MicroRNAs predominantly decrease gene expression; however, specific mRNAs are translationally upregulated in quiescent (G0) mammalian cells and immature Xenopus laevis oocytes by an FXR1a-associated microRNA-protein complex (microRNP) that lacks the microRNP repressor, GW182. Their mechanism in these conditions of decreased mTOR signaling, and therefore reduced canonical (cap-and-poly(A)-tail-mediated) translation, remains undiscovered. Our data reveal that mTOR inhibition in human THP1 cells enables microRNA-mediated activation. Activation requires shortened/no poly(A)-tail targets; polyadenylated mRNAs are partially activated upon PAIP2 overexpression, which interferes with poly(A)-bound PABP, precluding PABP-enhanced microRNA-mediated inhibition and canonical translation. Consistently, inhibition of PARN deadenylase prevents activation. P97/DAP5, a homolog of canonical translation factor, eIF4G, which lacks PABP- and cap binding complex-interacting domains, is required for activation, and thereby for the oocyte immature state. P97 interacts with 3' UTR-binding FXR1a-associated microRNPs and with PARN, which binds mRNA 5' caps, forming a specialized complex to translate recruited mRNAs in these altered canonical translation conditions.

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Species referenced: Xenopus laevis
Genes referenced: eif4g1 eif4g2 mtor pabpc4 parn tnrc6a

References [+] :
Beilharz, microRNA-mediated messenger RNA deadenylation contributes to translational repression in mammalian cells. 2009, Pubmed