Widespread JNK-dependent alternative splicing induces a positive feedback loop through CELF2-mediated regulation of MKK7 during T-cell activation
- Nicole M. Martinez1,2,
- Laura Agosto1,2,
- Jinsong Qiu3,
- Michael J. Mallory1,
- Matthew R. Gazzara1,4,
- Yoseph Barash4,
- Xiang-dong Fu3 and
- Kristen W. Lynch1,2,4
- 1Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA;
- 2Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA;
- 3Department of Cell and Molecular Medicine, University of California at San Diego, San Diego, California 92093, USA;
- 4Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennysylvania 19104, USA
- Corresponding author: klync{at}mail.med.upenn.edu
Abstract
Alternative splicing is prevalent among genes encoding signaling molecules; however, the functional consequence of differential isoform expression remains largely unknown. Here we demonstrate that, in response to T-cell activation, the Jun kinase (JNK) kinase MAP kinase kinase 7 (MKK7) is alternatively spliced to favor an isoform that lacks exon 2. This isoform restores a JNK-docking site within MKK7 that is disrupted in the larger isoform. Consistently, we show that skipping of MKK7 exon 2 enhances JNK pathway activity, as indicated by c-Jun phosphorylation and up-regulation of TNF-α. Moreover, this splicing event is itself dependent on JNK signaling. Thus, MKK7 alternative splicing represents a positive feedback loop through which JNK promotes its own signaling. We further show that repression of MKK7 exon 2 is dependent on the presence of flanking sequences and the JNK-induced expression of the RNA-binding protein CELF2, which binds to these regulatory elements. Finally, we found that ∼25% of T-cell receptor-mediated alternative splicing events are dependent on JNK signaling. Strikingly, these JNK-dependent events are also significantly enriched for responsiveness to CELF2. Together, our data demonstrate a widespread role for the JNK–CELF2 axis in controlling splicing during T-cell activation, including a specific role in propagating JNK signaling.
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Footnotes
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Supplemental material is available for this article.
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Article is online at http://www.genesdev.org/cgi/doi/10.1101/gad.267245.115.
- Received June 10, 2015.
- Accepted September 4, 2015.
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