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J Exp Med. 2013 Feb 11;210(2):417-32. doi: 10.1084/jem.20111717. Epub 2013 Feb 4.

T cell activation induces proteasomal degradation of Argonaute and rapid remodeling of the microRNA repertoire.

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  • 1Sandler Asthma Basic Research Center, University of California San Francisco, San Francisco, CA 94143, USA.

Abstract

Activation induces extensive changes in the gene expression program of naive CD4(+) T cells, promoting their differentiation into helper T cells that coordinate immune responses. MicroRNAs (miRNAs) play a critical role in this process, and miRNA expression also changes dramatically during T cell differentiation. Quantitative analyses revealed that T cell activation induces global posttranscriptional miRNA down-regulation in vitro and in vivo. Argonaute (Ago) proteins, the core effector proteins of the miRNA-induced silencing complex (miRISC), were also posttranscriptionally down-regulated during T cell activation. Ago2 was inducibly ubiquitinated in activated T cells and its down-regulation was inhibited by the proteasome inhibitor MG132. Therefore, activation-induced miRNA down-regulation likely occurs at the level of miRISC turnover. Measurements of miRNA-processing intermediates uncovered an additional layer of activation-induced, miRNA-specific transcriptional regulation. Thus, transcriptional and posttranscriptional mechanisms cooperate to rapidly reprogram the miRNA repertoire in differentiating T cells. Altering Ago2 expression in T cells revealed that Ago proteins are limiting factors that determine miRNA abundance. Naive T cells with reduced Ago2 and miRNA expression differentiated more readily into cytokine-producing helper T cells, suggesting that activation-induced miRNA down-regulation promotes acquisition of helper T cell effector functions by relaxing the repression of genes that direct T cell differentiation.

PMID:
23382546
[PubMed - indexed for MEDLINE]
PMCID:
PMC3570096
Free PMC Article
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