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MicroRNA-155 targets SMAD2 and modulates the response of macrophages to transforming growth factor-{beta}.

ABSTRACT: Transforming growth factor-beta (TGF-?) is a pleiotropic cytokine with important effects on processes such as fibrosis, angiogenesis, and immunosupression. Using bioinformatics, we identified SMAD2, one of the mediators of TGF-? signaling, as a predicted target for a microRNA, microRNA-155 (miR-155). MicroRNAs are a class of small non-coding RNAs that have emerged as an important class of gene expression regulators. miR-155 has been found to be involved in the regulation of the immune response in myeloid cells. Here, we provide direct evidence of binding of miR-155 to a predicted binding site and the ability of miR-155 to repress SMAD2 protein expression. We employed a lentivirally transduced monocyte cell line (THP1-155) containing an inducible miR-155 transgene to show that endogenous levels of SMAD2 protein were decreased after sustained overexpression of miR-155. This decrease in SMAD2 led to a reduction in both TGF-?-induced SMAD-2 phosphorylation and SMAD-2-dependent activation of the expression of the CAGA(12)LUC reporter plasmid. Overexpression of miR-155 altered the cellular responses to TGF-? by changing the expression of a set of genes that is involved in inflammation, fibrosis, and angiogenesis. Our study provides firm evidence of a role for miR-155 in directly repressing SMAD2 expression, and our results demonstrate the relevance of one of the two predicted target sites in SMAD2 3'-UTR. Altogether, our data uncover an important role for miR-155 in modulating the cellular response to TGF-? with possible implications in several human diseases where homeostasis of TGF-? might be altered.

SUBMITTER: Louafi F

PROVIDER: S-EPMC3009858 | biostudies-other | 2010 Dec

REPOSITORIES: biostudies-other

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MicroRNA-155 targets SMAD2 and modulates the response of macrophages to transforming growth factor-{beta}.

Louafi Fethi F Martinez-Nunez Rocio T RT Sanchez-Elsner Tilman T

The Journal of biological chemistry 20101029 53

Transforming growth factor-beta (TGF-β) is a pleiotropic cytokine with important effects on processes such as fibrosis, angiogenesis, and immunosupression. Using bioinformatics, we identified SMAD2, one of the mediators of TGF-β signaling, as a predicted target for a microRNA, microRNA-155 (miR-155). MicroRNAs are a class of small non-coding RNAs that have emerged as an important class of gene expression regulators. miR-155 has been found to be involved in the regulation of the immune response i ...[more]

PMID: 21036908

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Project description:BACKGROUND:The simplicity of Transforming Growth Factor ß (TGF?) signaling pathway, linear and non-amplified, hardly sustains its variety of responses. This is often justified by the complex regulation showed by Smad proteins, TGF? signaling intracellular transducers, object of post-translational modifications that modulate TGF?-dependent transcription. Protein acetylation is emerging as a compelling mechanism affecting the activities of significant transcription factors, including p53, FOXO or NF-kB. Smad proteins might be controlled by this mechanism, implying that accessory factors capable of altering Smads-transcriptional complexes acetylation status and hence regulate TGF? responses remain to be identified. Understanding this interaction may help in the assessment of TGF? signaling outcomes, extending from healthy physiology to pathological conditions and cancer. METHODS:A two-hybrid chimera interacting system allowed to identify Sirt1, a NAD+ dependent type III histone deacetylase, as a novel Smad2 interactor. Several well stablished cellular models were applied to characterize this interaction by means of co-immunoprecipitation of tagged proteins and immuno-fluorescence staining. The occurrence of the interaction at Smad2 driven transcriptomic complexes was studied by means of DNA-pull-down and chromatin immunoprecipitation (ChIP), while its effects were assessed by protein over-expression and siRNA applied into a TGF?-dependent reporter gene assay. RESULTS:The interaction was confirmed and observed to be enhanced upon Smad2 acetylation, a known feature of active and nuclear Smad2. However, Sirt1 did not play a major role in Smad2 deacetylation. Anti-Sirt1 ChIP showed increased recovery of promoter regions corresponding to Smad2-driven genes after TGF?-stimulation, while its occurrence at Smad2-dependent transcriptomic complexes on DNA was found to effectively modulate gene expression. CONCLUSIONS:Sirt1 presence on Smad2-driven TGF?-dependent regulatory elements was detected and found to increase after TGF? treatment. Moreover, Sirt1 overexpression resulted in a decrease of the activity of a Smad2-driven TGF?-dependent reporter gene, while Sirt1 interference increased its activity. This would confirm the relevance of the discovered Sirt1-Smad2 interaction for the regulation of TGF?-dependent gene transcription.

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MicroRNA-155 targets SMAD2 and modulates the response of macrophages to transforming growth factor-{beta}.

Publications

MicroRNA-155 targets SMAD2 and modulates the response of macrophages to transforming growth factor-{beta}.

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