MicroRNA Inhibition of Translation Initiation in Vitro by Targeting the Cap-Binding Complex eIF4F

Abstract

MicroRNAs (miRNAs) play an important role in gene regulatory networks in animals. Yet, the mechanistic details of their function in translation inhibition or messenger RNA (mRNA) destabilization remain controversial. To directly examine the earliest events in this process, we have developed an in vitro translation system using mouse Krebs-2 ascites cell-free extract that exhibits an authentic miRNA response. We show here that translation initiation, specifically the 5' cap recognition process, is repressed by endogenous let-7 miRNAs within the first 15 minutes of mRNA exposure to the extract when no destabilization of the transcript is observed. Our results indicate that inhibition of translation initiation is the earliest molecular event effected by miRNAs. Other mechanisms, such as mRNA degradation, may subsequently consolidate mRNA silencing.

Molecular medicine of microRNAs: structure, function and implications for diabetes

“…2); it still remains to be deciphered which of these model mechanisms are cause and consequence of translational repression. miRNAs affecting initiation steps only affect capdependent translation, possibly through m 7 G cap recognition (Refs 46,47,48,49,50). Argonaute proteins contain structural similarities to the cap-binding protein eIF4E, and thus it has been suggested that translational repression may occur due to competition between argonaute and eIF4E for binding to the cap structure (Ref.…”

Micro‐RNA‐155‐mediated control of heme oxygenase 1 (HO‐1) is required for restoring adaptively tolerant CD4+ T‐cell function in rodents

“…We next tested miR-155-dependent AGO2 binding to HO-1 mRNA by IP with AGO2-specific monoclonal antibodies from purified miR-155 +/+ adaptively tolerant CD4 + T cells. AGO2 is part of the protein complex that, specifically directed by miRNAs, transcriptionally represses mRNA targets [5,6]. Thus, if HO-1 is a target of miR-155 in tolerant T cells, HO-1 mRNA and miR-155 should be coimmunoprecipitated together with AGO2.…”

“…Micro-RNAs (miRNAs) are small genome-encoded RNAs that regulate gene expression by targeting complementary messenger RNAs (mRNAs) and block their translation [5,6]. The first C 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.eji-journal.eu…”

“…Recent experimental evidence indicates that this unresponsive state is maintained by the inhibition of signaling events, particularly downstream proximal signals of the T-cell receptor, that in turn promotes T-cell dysfunction [1][2][3][4]. Since the attenuation of T-cell effector functions by the programmed death receptor 1 (PD-1) pathway has been demonstrated in various chronic infectious diseases and cancer and in the control of autoimmune T cells, the modulation of this inhibitory pathway is considered a promising means to control the function of T cells or enhance immune responses in patients.Micro-RNAs (miRNAs) are small genome-encoded RNAs that regulate gene expression by targeting complementary messenger RNAs (mRNAs) and block their translation [5,6]. The first C 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.eji-journal.eu…”

MicroRNA epigenetic alterations in human cancer: One step forward in diagnosis and treatment

“…30 In addition, inhibition of translational initiation by affected ribosome recruitment to the mRNA and targeting of the mRNA cap structure was proven in a study utilizing extracts from mouse Krebs-2 ascites cells. 31 The dilemma how miRNA ribonucleoprotein complexes (miRNPs) that are bound to the 3 0 UTR of a target mRNA interfere with translational initiation was resolved by Kiriakidou et al 32 They identified a motif (MC) within the Mid domain of Ago proteins, which bears significant similarity to the m 7 G cap-binding domain of eIF4E, an essential translation initiation factor. In their model, the Ago proteins compete with eIF4E for cap binding and thus repress the translational initiation.…”