Interleukin-2-mediated NF-κB-dependent mRNA splicing modulates interferon gamma protein production.

Interferon-gamma (IFNγ) is a pleiotropic cytokine produced by natural killer (NK) cells during the early infection response. IFNγ expression is tightly regulated to mount sterilizing immunity while preventing tissue pathology. Several post-transcriptional effectors dampen IFNγ expression through IFNG mRNA degradation. In this study, we identify mRNA splicing as a positive regulator of IFNγ production. While treatment with the combination of IL-12 and IL-2 causes synergistic induction of IFNG mRNA and protein, defying transcription-translation kinetics, we observe that NK cells treated with IL-12 alone transcribe IFNG with introns intact. When NK cells are treated with both IL-2 and IL-12, IFNG transcript is spliced to form mature mRNA with a concomitant increase in IFNγ protein. We find that IL-2-mediated intron splicing occurs independently of nascent transcription but relies upon NF-κB signaling. We propose that while IL-12 transcriptionally induces IFNG mRNA, IL-2 signaling stabilizes IFNG mRNA by splicing detained introns, allowing for rapid IFNγ protein production. This study uncovers a novel role for cytokine-induced splicing in regulating IFNγ through a mechanism potentially applicable to other inflammatory mediators.