SUMOylation Regulates the Transcriptional Activity of JunB in T Lymphocytes

Abstract

The AP-1 family member JunB is a critical regulator of T cell function. JunB is a transcriptional activator of various cytokine genes, such as IL-2, IL-4, and IL-10; however, the post-translational modifications that regulate JunB activity in T cells are poorly characterized. We show here that JunB is conjugated with small ubiquitin-like modifier (SUMO) on lysine 237 in resting and activated primary T cells and T cell lines. Sumoylated JunB associated with the chromatin-containing insoluble fraction of cells, whereas nonsumoylated JunB was also in the soluble fraction. Blocking JunB sumoylation by mutation or use of a dominant-negative form of the SUMO-E2 Ubc-9 diminished its ability to transactivate IL-2 and IL-4 reporter genes. In contrast, nonsumoylable JunB mutants showed unimpaired activity with reporter genes controlled by either synthetic 12-O-tetradecanoylphorbol-13-acetate response elements or NF-AT/AP-1 and CD28RE sites derived from the IL-2 promoter. Ectopic expression of JunB in activated human primary CD4+ T cells induced activation of the endogenous IL-2 promoter, whereas the nonsumoylable JunB mutant did not. Thus, our work demonstrates that sumoylation of JunB regulates its ability to induce cytokine gene transcription and likely plays a critical role in T cell activation.

Sumoylation and Nuclear Translocation of S100A4 Regulate IL-1β-mediated Production of Matrix Metalloproteinase-13

“…Ubc9 is an E2-conjugating enzyme that transfers the sumo protein to the acceptor lysine residue on the target protein (35). Expression of DN-Ubc9 (C93S and L97S) has been previously shown to inhibit sumoylation (36). In support of our data, another study showed the presence of modified forms of S100A4 in nuclear extracts of the colorectal cancer cell line SW620, suggesting the presence of post-translational modification (37).…”

JUNB/AP-1 controls IFN-γ during inflammatory liver disease

“…We also observed that JUNB deletion leads to decreased IL-2 production in T cells from ConA-or αGalCer-treated mice, consistent with in vitro experiments demonstrating that AP-1 modulates IL-2 transcription in T cells (18,19,47). IL-2 triggers NK cell proliferation and activation (48) and increases IFN-γ expression in T cells (49) and NK cells (48).…”

Expression analysis of Ubc9, the single small ubiquitin-like modifier (SUMO) E2 conjugating enzyme, in normal and malignant tissues

“…To date, little information is available regarding a role of Ubc9 and, by extension, sumoylation in the immune system [29,30]. However, it has been reported that Ubc9 modulates the activity of some transcription factors that regulate inflammatory response, such as nuclear factor κB, and STAT1 [29,31,32].…”