BATF is a nuclear basic leucine zipper protein that belongs to the AP-1/ATF superfamily of transcription factors. The leucine zipper of this protein mediates dimerization with members of the Jun family of proteins. This protein is thought to be a negative regulator of AP-1/ATF transcriptional events and blocks cellular transformation by Ras and Fos. BATF also is required for the differentiation of IL-17-producing T helper (TH17) cells, a CD4+ subset of T cells that coordinates the inflammatory response in host defense. In both T cells and B cells, BATF is required for the appropriate regulation of the class-switch recombination.Synonyms: B-ATF, B-cell activating transcription factor, Basic leucine zipper transcriptional factor ATF-like, SF-HT-activated gene 2 protein, SFA-2, SFA2