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Cited by 5,287MicroRNA in disease regulationPlant Molecular Biology ResearchRNA Interference and Gene Delivery

Overview of MicroRNA Biogenesis, Mechanisms of Actions, and Circulation

Open access
O'Brien, Jacob, Hayder, Heyam, Zayed, Yara, Peng, Chun·2018·Frontiers in Endocrinology
DOI 10.3389/fendo.2018.00402PMC PMC6085463
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Abstract

MicroRNAs (miRNAs) are a class of non-coding RNAs that play important roles in regulating gene expression. The majority of miRNAs are transcribed from DNA sequences into primary miRNAs and processed into precursor miRNAs, and finally mature miRNAs. In most cases, miRNAs interact with the 3' untranslated region (3' UTR) of target mRNAs to induce mRNA degradation and translational repression. However, interaction of miRNAs with other regions, including the 5' UTR, coding sequence, and gene promoters, have also been reported. Under certain conditions, miRNAs can also activate translation or regulate transcription. The interaction of miRNAs with their target genes is dynamic and dependent on many factors, such as subcellular location of miRNAs, the abundancy of miRNAs and target mRNAs, and the affinity of miRNA-mRNA interactions. miRNAs can be secreted into extracellular fluids and transported to target cells via vesicles, such as exosomes, or by binding to proteins, including Argonautes. Extracellular miRNAs function as chemical messengers to mediate cell-cell communication. In this review, we provide an update on canonical and non-canonical miRNA biogenesis pathways and various mechanisms underlying miRNA-mediated gene regulations. We also summarize the current knowledge of the dynamics of miRNA action and of the secretion, transfer, and uptake of extracellular miRNAs.

AI snapshot

Written from the paper’s full text.

TL;DR

This review summarizes microRNA biogenesis, mechanisms of action, dynamic subcellular regulation, and extracellular circulation. It highlights miRNAs as both gene regulators and intercellular signals while noting unresolved questions about nuclear function, translational activation, and secretion/uptake.

Key findings

  • Canonical miRNA biogenesis involves pri-miRNA processing by Drosha/DGCR8, export by XPO5/RanGTP, Dicer cleavage into a mature duplex, and loading of the 5p or 3p strand into AGO1–4; non-canonical pathways include Drosha/DGCR8-independent mirtrons and m7G-capped pre-miRNAs, and Dicer-independent AGO2-dependent processing.
  • Most miRNAs bind 3′ UTR miRNA response elements to induce translational repression and mRNA deadenylation, decapping, and degradation via GW182, PAN2/3, CCR4-NOT, DCP2, and XRN1; binding to 5′ UTR/coding regions can silence, promoter binding can induce transcription, and activation occurs under specific conditions such as serum starvation, cell cycle arrest, oocytes, and amino acid starvation.
  • miRNA action is dynamic: miRISC localizes to rER, P-bodies, stress granules, endosomes, multivesicular bodies, mitochondria, and the nucleus; average polysome occupancy is below 40%, and FANTOM5 data indicate that the top five expressed miRNAs represent on average ~50% of the miRNA pool in a given human cell type, with about half cell-type enriched and one quarter broadly expressed.
  • Extracellular miRNAs are highly stable, resisting room-temperature degradation for up to 4 days and conditions such as boiling, freeze-thaw cycles, and high or low pH; they circulate in vesicles or bound to proteins such as AGO2, HDL, and NPM1, and can act as autocrine, paracrine, or endocrine signals, including via Toll-like receptors.

Methods

  • Narrative review; no primary experimental data, systematic search strategy, or sample size is reported.
  • The main analysis is a thematic synthesis of published literature on canonical and non-canonical biogenesis, miRNA-mediated gene regulation, subcellular dynamics, and extracellular miRNA circulation.
  • Data/sample: not applicable; the paper synthesizes prior studies and includes proposed models in figures.

Limitations

  • The paper states that understanding of when and how miRNAs regulate transcription is limited, conditions for translational activation need further exploration, and mechanisms of extracellular miRNA secretion and uptake are not well understood.
  • The paper notes that many studies use in vitro transfection into immortalized or cancer cell lines, which may not reflect endogenous miRNA functions in vivo, and that chemical tags on miRNAs could affect miRNA:MRE or AGO:miRNA interactions.
  • Evident from the text: as a narrative review, it does not systematically assess evidence quality or quantify effect sizes across the cited literature.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.3389/fendo.2018.00402

Cites

144 of 144 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 127 cited sources checked · 0 supported · 0 flagged

  • Premisecitation

    In serum starved cells, AGO2 and FXR1 were associated with AU-rich elements at the 3' UTR to activate translation.

    “In serum starved cells, AGO2 and another protein related to the miRNA-protein complex (microRNPs), Fragile-x-mental retardation related protein 1 (FXR1), were associated with AU-rich elements (AREs) at 3′ UTR to activate translation (55).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [55] Vasudevan, 2007, AU-rich-element-mediated upregulation of translation by FXR1 and Argonaute 2, Cell source

      Not checked in the free run.

  • Premisecitation

    In most cases, miRNAs interact with the 3' UTR of target mRNAs to induce mRNA degradation and translational repression.

    “In most cases, miRNAs interact with the 3′ untranslated region (3′ UTR) of target mRNAs to induce mRNA degradation and translational repression.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [14] Ha, 2014, Regulation of microRNA biogenesis, Nat Rev Mol Cell Biol. source

      Not checked in the free run.

  • Premisecitation

    Extracellular miRNAs function as chemical messengers to mediate cell-cell communication.

    “Extracellular miRNAs function as chemical messengers to mediate cell-cell communication.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [21] Hayes, 2014, MicroRNAs in cancer: biomarkers, functions and therapy, Trends Mol Med. source

      Not checked in the free run.

    • cites [22] Wang, 2016, MicroRNA as Biomarkers and Diagnostics, J Cell Physiol. source

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    • cites [23] Huang, 2017, MicroRNAs: biomarkers, diagnostics, and therapeutics, Methods Mol Biol. source

      Not checked in the free run.

  • Premisecitation

    In the canonical pathway, pri-miRNAs are processed into pre-miRNAs by the microprocessor complex consisting of DGCR8 and Drosha.

    “In this pathway, pri-miRNAs are transcribed from their genes and then processed into pre-miRNAs by the microprocessor complex, consisting of an RNA binding protein DiGeorge Syndrome Critical Region 8 (DGCR8) and a ribonuclease III enzyme, Drosha (27).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [27] Denli, 2004, Processing of primary microRNAs by the Microprocessor complex, Nature source

      Not checked in the free run.

  • Premisecitation

    miRNA interaction with promoter region has been reported to induce transcription.

    “while miRNA interaction with promoter region has been reported to induce transcription (45).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [45] Dharap, 2013, MicroRNA miR-324-3p induces promoter-mediated expression of RelA gene, PLoS ONE source

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  • May combine two claims. 29
  • Classified as probably not a substantial claim. 13

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    Premisecitation

    Under certain conditions, miRNAs can activate translation or regulate transcription.

    “Under certain conditions, miRNAs can also activate translation or regulate transcription.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [16] Vasudevan, 2012, Posttranscriptional upregulation by microRNAs, Wiley Interdiscip Rev RNA source

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    Premisecitation

    The formation of a silencing miRISC complex starts with the recruitment of the GW182 family of proteins by miRISC; GW182 provides the scaffolding needed to recruit other effector proteins such as the poly(A)-deadenylase complexes PAN2-PAN3 and CCR4-NOT following miRNA:target mRNA interaction.

    “The formation of a silencing miRISC complex starts with the recruitment of the GW182 family of proteins by miRISC; GW182 provides the scaffolding needed to recruit other effector proteins (52), such as the poly(A)-deadenylase complexes PAN2-PAN3 and CCR4-NOT, following miRNA:target mRNA interaction (50, 53).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [52] Behm-Ansmant, 2006, mRNA degradation by miRNAs and GW182 requires both CCR4:NOT deadenylase and DCP1:DCP2 decapping complexes, Genes Dev. source

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    • cites [50] Jonas, 2015, Towards a molecular understanding of microRNA-mediated gene silencing, Nat Rev Genet. source

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    • cites [53] Christie, 2013, Structure of the PAN3 pseudokinase reveals the basis for interactions with the PAN2 deadenylase and the GW182 proteins, Mol Cell. source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Mirtrons are produced from the introns of mRNA during splicing.

    “An example of such pre-miRNAs is mirtrons, which are produced from the introns of mRNA during splicing (35, 36).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [35] Ruby, 2007, Intronic microRNA precursors that bypass Drosha processing, Nature source

      Not checked in the free run.

    • cites [36] Babiarz, 2008, Mouse ES cells express endogenous shRNAs, siRNAs, and other Microprocessor-independent, Dicer-dependent small RNAs, Genes Dev. source

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  • May combine two claims.

    Premisecitation

    Dicer-independent miRNAs are processed by Drosha from endogenous short hairpin RNA transcripts and require AGO2 to complete their maturation within the cytoplasm.

    “On the other hand, Dicer-independent miRNAs are processed by Drosha from endogenous short hairpin RNA (shRNA) transcripts (38). These pre-miRNAs require AGO2 to complete their maturation within the cytoplasm because they are of insufficient length to be Dicer-substrates (38).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [38] Yang, 2010, Conserved vertebrate mir-451 provides a platform for Dicer-independent, Ago2-mediated microRNA biogenesis, Proc Natl Acad Sci USA. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Several miRNAs including let-7 were found to be associated with AGO2 and FXR1 to activate translation during cell cycle arrest, but they inhibit translation in proliferating cells.

    “Several miRNAs, including let-7, were found to be associated with AGO2 and FXR1 to activate translation during cell cycle arrest, but they inhibit translation in proliferating cells (55).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [55] Vasudevan, 2007, AU-rich-element-mediated upregulation of translation by FXR1 and Argonaute 2, Cell source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    About half of all currently identified miRNAs are intragenic and processed mostly from introns and relatively few exons of protein coding genes, while the remaining are intergenic, transcribed independently of a host gene and regulated by their own promoters.

    “About half of all currently identified miRNAs are intragenic and processed mostly from introns and relatively few exons of protein coding genes, while the remaining are intergenic, transcribed independently of a host gene and regulated by their own promoters (13, 24).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [13] de Rie, 2017, An integrated expression atlas of miRNAs and their promoters in human and mouse, Nat Biotechnol. source

      Not checked in the free run.

    • cites [24] Kim, 2007, Processing of intronic microRNAs, EMBO J. source

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  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    The interaction of miRNAs with their target genes is dynamic and dependent on factors such as subcellular location of miRNAs, abundancy of miRNAs and target mRNAs, and affinity of miRNA-mRNA interactions.

    “The interaction of miRNAs with their target genes is dynamic and dependent on many factors, such as subcellular location of miRNAs, the abundancy of miRNAs and target mRNAs, and the affinity of miRNA-mRNA interactions.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Pre-miRNAs are exported to the cytoplasm by an XPO5/RanGTP complex and then processed by Dicer.

    “Once pre-miRNAs are generated, they are exported to the cytoplasm by an exportin 5 (XPO5)/RanGTP complex and then processed by the RNase III endonuclease Dicer (27, 30).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [27] Denli, 2004, Processing of primary microRNAs by the Microprocessor complex, Nature source

      Not checked in the free run.

    • cites [30] Okada, 2009, A high-resolution structure of the pre-microRNA nuclear export machinery, Science source

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  • May combine two claims.

    Premisecitation

    miRNAs are critical for normal animal development and are involved in a variety of biological processes.

    “miRNAs are critical for normal animal development and are involved in a variety of biological processes (18).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [18] Fu, 2013, MicroRNAs in human placental development and pregnancy complications, Int J Mol Sci. source

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    Premisecitation

    miRNAs interact at genomic loci where enhancer-derived RNA are transcribed and increase mRNA levels of adjacent genes by promoting a transcriptionally active chromatin state while altering alternative splicing profiles.

    “miRNAs have also been shown to interact at genomic loci, where enhancer-derived RNA (eRNA) are transcribed, and increase mRNA levels of adjacent genes by promoting a transcriptionally active chromatin state (67) while altering alternative splicing profiles (64).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [67] Xiao, 2017, MicroRNAs activate gene transcription epigenetically as an enhancer trigger, RNA Biol. source

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    • cites [64] Allo, 2014, Argonaute-1 binds transcriptional enhancers and controls constitutive and alternative splicing in human cells, Proc Natl Acad Sci USA. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Cooperation of multiple proximal MREs on target mRNA increases RNAi activity and increases retention times of miRISC complexes on those mRNA.

    “Cooperation of multiple, proximal MREs on target mRNA has been shown to increase RNAi activity and increase retention times of miRISC complexes on those mRNA, most likely through the three AGO binding sites on the GW182 family proteins (94, 100).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [94] Denzler, 2016, Impact of MicroRNA levels, target-site complementarity, and cooperativity on competing endogenous RNA-regulated gene expression, Mol Cell source

      Not checked in the free run.

    • cites [100] Elkayam, 2017, Multivalent recruitment of human argonaute by GW182, Mol Cell. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Alternative splicing and alternative polyadenylation affecting 3' UTRs, and cell type-specific RNA binding proteins that affect target mRNA secondary structures, change the available pool of MREs.

    “Alternative splicing and alternative polyadenylation affecting 3′ UTRs, and cell type-specific RNA binding proteins that affect target mRNA secondary structures, change the available pool of MREs (63, 68, 69).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [63] Bottini, 2017, Post-transcriptional gene silencing mediated by microRNAs is controlled by nucleoplasmic Sfpq, Nat Commun. source

      Not checked in the free run.

    • cites [68] Nam, 2014, Global analyses of the effect of different cellular contexts on microRNA targeting, Mol Cell. source

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    • cites [69] Blazie, 2017, Alternative polyadenylation directs tissue-specific miRNA targeting in Caenorhabditis elegans Somatic Tissues, Genetics source

      Not checked in the free run.

  • May combine two claims.

    Interpretationnone given

    miRNA-mediated gene regulation is dynamic and helps to buffer gene expression to a steady state.

    “Studies have revealed that miRNA-mediated gene regulation is dynamic and helps to buffer gene expression to a steady state.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Nuclear localized miRISC regulates both transcriptional rates and post-transcriptional levels of mRNA and associates with euchromatin at gene loci with active transcription.

    “Nuclear localized miRISC was found to regulate both transcriptional rates and post-transcriptional levels of mRNA (59–61) and associate with euchromatin at gene loci with active transcription (62).”
    Quote in the paperNot a substantial claim0 of 4 sources checked
    • cites [59] Nishi, 2013, Human TNRC6A is an Argonaute-navigator protein for microRNA-mediated gene silencing in the nucleus, RNA source

      Not checked in the free run.

    • cites [60] Benhamed, 2012, Senescence is an endogenous trigger for microRNA-directed transcriptional gene silencing in human cells, Nat Cell Biol. source

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    • cites [61] Pitchiaya, 2017, Resolving subcellular miRNA trafficking and turnover at single-molecule resolution, Cell Rep. source

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    • cites [62] Cernilogar, 2011, Chromatin-associated RNA interference components contribute to transcriptional regulation in Drosophila, Nature source

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  • May combine two claims.

    Premisecitation

    Approximately half of the expressed miRNAs are cell type enriched, one quarter are broadly expressed, and the remaining had low-level expression regardless of cell type.

    “Moreover, approximately half of the expressed miRNAs are cell type enriched, one quarter are broadly expressed, and the remaining had low-level expression regardless of cell type.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [13] de Rie, 2017, An integrated expression atlas of miRNAs and their promoters in human and mouse, Nat Biotechnol. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    miRISC has been found to copurify with polysomes, and the miRISC:mRNA complexes bound to these polysomes were associated with increased levels of translational inhibition and mRNA degradation.

    “miRISC has also been found to copurify with polysomes, and the miRISC:mRNA complexes bound to these polysomes were associated with increased levels of translational inhibition and mRNA degradation (83).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [83] Pillai, 2005, Inhibition of translational initiation by Let-7 MicroRNA in human cells, Science source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    miRNAs, AGO2, and target mRNAs are associated with rER-membrane-bound polysomes, and this occurs before miRNA-mediated translational repression.

    “A recent study showed that miRNAs, AGO2, and target mRNAs are associated with rER-membrane-bound polysomes, and this occurs before miRNA-mediated translational repression (70).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [70] Barman, 2015, mRNA targeting to endoplasmic reticulum precedes ago protein interaction and microRNA (miRNA)-mediated translation repression in mammalian cells, J Biol Chem. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    CDKN1A is targeted by at least 28 miRNAs, many of which are upregulated together in cancers where CDKN1A has been implicated.

    “For example, cyclin-dependent kinase inhibitor 1A (CDKN1A), a tumor suppressor that is downregulated in multiple cancers (106), is targeted by at least 28 miRNAs and many of which are upregulated together in cancers where CDKN1A has been implicated (107).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [106] Abbas, 2009, p21 in cancer: intricate networks and multiple activities, Nat Rev Cancer source

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    • cites [107] Wu, 2010, Multiple microRNAs modulate p21Cip1/Waf1 expression by directly targeting its 3′ untranslated region, Oncogene source

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  • May combine two claims.

    Premisecitation

    The degree of polysome occupancy of target mRNAs is dependent on the affinity between miRNA seed region and MRE, but not on miRNA abundance.

    “Additionally, the degree of polysome occupancy of target mRNAs is dependent on the affinity between miRNA seed region and MRE, but not on miRNA abundance (84).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [84] Molotski, 2012, Differential association of microRNAs with polysomes reflects distinct strengths of interactions with their mRNA targets, RNA source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Extracellular miRNAs can be delivered to target cells and may act as autocrine, paracrine, and/or endocrine regulators to modulate cellular activities.

    “The extracellular miRNAs can be delivered to target cells and they may act as autocrine, paracrine, and/or endocrine regulators to modulate cellular activities (116).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [116] Iftikhar, 2016, Evidence and potential in vivo functions for biofluid miRNAs: from expression profiling to functional testing: potential roles of extracellular miRNAs as indicators of physiological change and as agents of intercellular information exchange, Bioessays source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Secretion of exosomal miRNAs is mediated by a ceramide-dependent pathway and the secreted miRNAs exert growth regulatory effects in target cells.

    “It has been shown that the secretion of exosomal miRNAs is mediated by a ceramide-dependent pathway and the secreted miRNAs exert growth regulatory effects in target cells (129).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [129] Kosaka, 2010, Secretory mechanisms and intercellular transfer of microRNAs in living cells, J Biol Chem. source

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  • May combine two claims.

    Premisecitation

    Both cell stress induced by heat shock and translation inhibition following treatment with hippuristanol or cycloheximide induced translocation of miRISC from the nucleus and cytoplasm to transient, cytoplasmic stress granules.

    “Both cell stress induced by heat shock and translation inhibition following treatment with hippuristanol or cycloheximide induced translocation of miRISC from the nucleus and cytoplasm to transient, cytoplasmic SG (72, 111).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [72] Detzer, 2011, Cell stress is related to re-localization of Argonaute 2 and to decreased RNA interference in human cells, Nucleic Acids Res. source

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    • cites [111] Leung, 2006, Quantitative analysis of Argonaute protein reveals microRNA-dependent localization to stress granules, Proc Natl Acad Sci USA. source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Several studies found that the majority of extracellular miRNAs are not associated with exosomes/microvesicles but are instead bound to AGO2.

    “While several studies found that the majority of extracellular miRNAs are not associated with exosomes/microvesicles but are instead bound to AGO2 (118, 125), another study reported that extracellular miRNAs are present predominantly in exosomes in human serum and saliva (120).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [118] Arroyo, 2011, Argonaute2 complexes carry a population of circulating microRNAs independent of vesicles in human plasma, Proc Natl Acad Sci USA source

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    • cites [125] Turchinovich, 2011, Characterization of extracellular circulating microRNA, Nucleic Acids Res. source

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  • May combine two claims.

    Premisecitation

    Extracellular miRNAs bind to Toll-like receptors, activate downstream signaling events, and lead to biological responses such as tumor growth, metastasis, and neurodegeneration.

    “Extracellular miRNAs have also been reported to bind to Toll-like receptors (137), activate downstream signaling events, and eventually lead to biological responses, such as tumor growth and metastasis (138), and neurodegeneration (139).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [137] Fabbri, 2018, MicroRNAs and miRceptors: a new mechanism of action for intercellular communication, Philos Trans R Soc Lond B Biol Sci. source

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    • cites [138] Fabbri, 2012, MicroRNAs bind to Toll-like receptors to induce prometastatic inflammatory response, Proc Natl Acad Sci USA. source

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    • cites [139] Lehmann, 2012, An unconventional role for miRNA: let-7 activates Toll-like receptor 7 and causes neurodegeneration, Nat Neurosci. source

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  • May combine two claims.

    Premisecitation

    Exosome-mediated transfer of miR-105 from metastatic breast cancer cells to endothelial cells directly targeted ZO-1, leading to destruction of endothelial barrier function and promoted metastasis.

    “For example, exosome mediated transfer of miR-105 from metastatic breast cancer cells to endothelial cells directly targeted a tight junction protein, zonula occludens 1 (ZO-1), and this led to the destruction of the barrier function of endothelium and promoted metastasis (134).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [134] Zhou, 2014, Cancer-secreted miR-105 destroys vascular endothelial barriers to promote metastasis, Cancer Cell source

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  • May combine two claims.

    Premisecitation

    The presence of miRNAs in vesicles or with accompanying proteins is generally thought to protect extracellular miRNAs and increase their stability in the extracellular milieu.

    “The presence of miRNAs in vesicles or with accompanying proteins is generally thought to protect extracellular miRNAs and increase their stability in the extracellular milieu (120).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [120] Gallo, 2012, The majority of microRNAs detectable in serum and saliva is concentrated in exosomes, PLoS ONE source

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  • May combine two claims.

    Premisecitation

    In PC12 cells, miRNA entry by endocytosis/micropinocytosis is dependent on clathrin, but not on caveolae or lipid rafts.

    “This process has been reported to be dependent on clathrin, but not on caveolae or lipid rafts in PC12 cells (142).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [142] Tian, 2014, Exosome uptake through clathrin-mediated endocytosis and macropinocytosis and mediating miR-21 delivery, J Biol Chem. source

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  • May combine two claims.

    Premisecitation

    In neuroendocrine cells, miRNAs in large dense-core vesicles are released by exocytosis through vesicle fusion, and this process is mediated by the SNARE complex and accelerated by Ca2+ stimulus.

    “In neuroendocrine cells, miRNAs in large dense-core vesicles (LDCVs) are released by exocytosis through vesicle fusion, and this process is mediated by the SNARE complex and accelerated by Ca2+ stimulus (131).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [131] Gumurdu, 2017, MicroRNA exocytosis by large dense-core vesicle fusion, Sci Rep. source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Another study reported that extracellular miRNAs are present predominantly in exosomes in human serum and saliva.

    “another study reported that extracellular miRNAs are present predominantly in exosomes in human serum and saliva (120).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [120] Gallo, 2012, The majority of microRNAs detectable in serum and saliva is concentrated in exosomes, PLoS ONE source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Two populations of extracellular miRNAs exist in biological fluids: one in vesicles such as exosomes, microvesicles, and apoptotic bodies, and the other associated with proteins, especially AGO2.

    “Two populations of extracellular miRNAs exist in biological fluids. One can be found in vesicles such as exosomes, microvesicles, and apoptotic bodies (116, 120) while the other is associated with proteins, especially AGO2 (120, 125).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [116] Iftikhar, 2016, Evidence and potential in vivo functions for biofluid miRNAs: from expression profiling to functional testing: potential roles of extracellular miRNAs as indicators of physiological change and as agents of intercellular information exchange, Bioessays source

      Not checked in the free run.

    • cites [120] Gallo, 2012, The majority of microRNAs detectable in serum and saliva is concentrated in exosomes, PLoS ONE source

      Not checked in the free run.

    • cites [125] Turchinovich, 2011, Characterization of extracellular circulating microRNA, Nucleic Acids Res. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Exosomes from umbilical cord blood are enriched in miR-21-3p, which promotes proliferation and migration of fibroblasts and induces angiogenic activities of endothelial cells, leading to accelerated wound healing.

    “Moreover, exosomes from umbilical cord blood were found to be enriched in miR-21-3p, which promoted the proliferation and migration of fibroblasts, and induced the angiogenic activities of endothelial cells, leading to accelerated wound healing (135).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [135] Hu, 2018, Exosomes from human umbilical cord blood accelerate cutaneous wound healing through miR-21-3p-mediated promotion of angiogenesis and fibroblast function, Theranostics source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Upon serum starvation of multiple human cell lines, there was an immediate exportation of stable, vesicular or vesicle-free miRNA and a concomitant decrease of intracellular miRNA levels.

    “In a study by Wang et al. (110), upon serum starvation of multiple human cell lines, there was an immediate exportation of stable, vesicular or vesicle-free miRNA and a concomitant decrease of intracellular miRNA levels (110).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [110] Wang, 2010, Export of microRNAs and microRNA-protective protein by mammalian cells, Nucleic Acids Res. source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Interpretationnone given

    Mechanisms by which miRNAs are secreted and taken up by cells are not well understood.

    “Mechanisms by which miRNAs are secreted and taken up by cells are not well understood and require further investigation.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Interpretationnone given

    miRNAs are powerful gene regulators.

    “It is now clear that miRNAs are powerful gene regulators, and that they not only help control mRNA stability and translation but are also involved in transcription.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Interpretationnone given

    miRNA activity in a test tube may not be recapitulated within the cellular environment.

    “The assaying of miRNA activity within a test tube may not be recapitulated within the cellular environment and thus should be viewed with caution.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationreasoning

    Chemical tags on miRNA could impact miRNA:MRE interaction or AGO:miRNA interactions, specifically with 5′ and 3′ miRNA nucleotide modifications.

    “Also, the addition of chemical tags to miRNA could also impact miRNA:MRE interaction or AGO:miRNA interactions, specifically with 5′ and 3′ miRNA nucleotide modifications.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given

    miRNAs are secreted and transferred to recipient cells.

    “miRNAs regulate the activity of host cells, and they are also secreted and transferred to recipient cells.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given

    Our understanding of when and how miRNAs can exert regulatory effects on transcription is limited.

    “However, our understanding of when and how miRNAs can exert regulatory effects on transcription is limited.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given

    Many factors contribute to the activity of miRNAs, including subcellular location, miRNA/mRNA abundance, miRNA:MRE affinity, cell type/state, and availability of various miRISC components.

    “Many factors contribute to the activity of miRNAs, including subcellular location, miRNA/mRNA abundance, miRNA:MRE affinity, cell type/state, and the availability of various miRISC components.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    Cytosolic miRISC components shuttle between different compartments.

    “Cytosolic miRISC components shuttle between different compartments.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Study design and conductnone given

    Most studies conducted so far were done in vitro using co-culture of different cell types.

    “However, most studies conducted so far were done in vitro using co-culture of different cell types.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    miRNAs in the nucleus play a role in regulating transcription and alternative splicing.

    “miRNAs in the nucleus play a role in regulating transcription and alternative splicing.”
    Quote in the paperNot a substantial claim
42 of 42

  • The paper relies on this without support.

    The first and last miRNA nucleotides clamp the miRNA within AGO proteins.

    “The first and last miRNA nucleotides clamp the miRNA within AGO proteins”
1 of 1

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Translation of any synthetic mRNA released into the cytoplasm may be blocked by micro ribonucleic acid.

    “Additionally, translation of any synthetic mRNA released into the cytoplasm may be blocked by micro ribonucleic acid (microRNA) [44].”

    From Relative risk reduction: Misinformative measure in clinical trials and COVID-19 vaccine efficacy (2022) · cites this paper as [44]

    The paper’s “Mechanisms of miRNA-mediated gene regulation” section says miRNAs repress translation by binding specific sequences in target mRNAs. Its “Subcellular compartmentalization of miRNAs” section also describes translational inhibition in the cytoplasm. It does not establish that any synthetic mRNA released into the cytoplasm can be blocked; targeting depends on a suitable binding sequence. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

  • Other non-coding regulatory mechanisms (miRNAs, lncRNAs, transposable elements) could alter gene expression in AD and are not assessed in this study.

    “Although this study is focused on identifying CREs, there are other non-coding regulatory mechanisms that could alter gene expression in AD including microRNAs (miRNAs),90 long non-coding RNAs (lncRNAs),91 transposable elements,92 etc., that are not assessed.”

    From Single nucleus multiomics identifies ZEB1 and MAFB as candidate regulators of Alzheimer’s disease-specific cis-regulatory elements (2023) · cites this paper as [90]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • miRNA identifier differs from the cited study

    Minor

    The text attributes suppression of CYP2E1 transcription to miR-522, but the title of the cited study identifies the miRNA as miR-552.

  • Flow condition differs from the cited study

    Minor

    The text describes the cited secretion finding as induced by atheroprotective laminar shear stress, whereas the cited study's title identifies disturbed flow as the inducing condition.

2 of 2

Cites

Flagged first, then by citations

2 of the 146 references couldn’t be matched to a known paper.

Cited by

Sorted by citations

Related

Authors
O'Brien, J., Hayder, H., Zayed, Y., & Peng, C.
Affiliations
York University (CA)
Corresponding author
Peng, Chun
ORCID
Venue
Frontiers in Endocrinology
Publisher
Frontiers Media SA
Published
2018-08-03
Volume
9
Pages
402-402
ISSN
1664-2392 (ISSN-L)
DOI
10.3389/fendo.2018.00402
PMC
PMC6085463
OpenAlex
W2811212358
Cited by
5,287
References
146
Citations by year
2026: 502 · 2025: 781 · 2024: 872 · 2023: 930 · 2022: 906 · 2021: 696 · 2020: 421 · 2019: 149 · 2018: 6 · 2017: 1 · 2015: 1 · 2014: 2 · 2013: 1 · 2012: 1
FWCI
33.05
Type
journal article
Language
en
Open access
Licence
Locations
  • Frontiers in Endocrinology (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
Canadian Institutes of Health Research (153146_1, MOP89931, 132565_1, 92222_1, MOP-81370)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cancer Research › MicroRNA in disease regulation
  • Life Sciences › Agricultural and Biological Sciences › Plant Science › Plant Molecular Biology Research
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › RNA Interference and Gene Delivery
Keywords
microRNA biogenesis, microRNA regulation of gene expression, 3' untranslated region, mRNA degradation, protein synthesis inhibition, Argonaute proteins, exosomes, extracellular miRNAs, intercellular communication

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-07.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-07.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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