Regulation of T cell differentiation by the AP-1 transcription factor JunB

JunB, a component of the activator protein-1 (AP-1) transcription factor, is known to exhibit an important role in bone formation and bone marrow cell proliferation. During T helper type 2 (Th2) cell differentiation, JunB contributes to the regulation of interleukin (IL)-4 expression, and AP-1 and nuclear factor of activated T cell (NFAT) constitute a heteromer and contribute to IL-2 production. However, the role of JunB in other T cells has not been investigated. In 2017, it was revealed that JunB, in collaboration with basic leucine zipper ATF-like transcription factor (BATF), regulates the expression of Th17-related genes. Furthermore, JunB was found to play an important role in regulatory T (Treg) cell differentiation, contributing to CD25 expression and IL-2 production. IL-2 is a T cell activator and has been shown as a necessary factor for Treg proliferation. Here, we review the role of JunB in T cells based on basic research data and discuss the potential for its clinical applications.