Bach2 represses the AP-1-driven induction of interleukin-2 gene transcription in CD4⁺ T cells

The transcription repressor Bach2 has been proposed as a regulator of T cell quiescence, but the underlying mechanism is not fully understood. Given the importance of interleukin-2 in T cell activation, we investigated whether Bach2 is a component of the network of factors that regulates interleukin-2 expression. In primary and transformed CD4⁺ T cells, Bach2 overexpression counteracted T cell receptor/CD28- or PMA/ ionomycin-driven induction of interleukin-2 expression, and silencing of Bach2 had the opposite effect. Luciferase and chromatin immunoprecipitation assays revealed that Bach2 binds to multiple Maf-recognition element-like sites on the interleukin-2 proximal promoter in a manner competitive with AP-1, and thereby represses AP-1-driven induction of interleukin-2 transcription. Thus, this study demonstrates that Bach2 is a direct repressor of the interleukin-2 gene in CD4⁺ T cells during the immediate early phase of AP-driven activation, thereby playing an important role in the maintenance of immune quiescence in the steady state.