Sequence specific transcriptional activator which binds to the PU-box, a purine-rich DNA sequence (5'-GAGGAA-3') that can act as a lymphoid-specific enhancer. Promotes development of plasmacytoid dendritic cells (pDCs), also known as type 2 DC precursors (pre-DC2) or natural interferon (IFN)-producing cells. These cells have the capacity to produce large amounts of interferon and block viral replication. Required for B-cell receptor (BCR) signaling, which is necessary for normal B-cell development and antigenic stimulation. Can form homotypic interactions. Interacts with IRF4. May also interact with CREBBP, EP300, SPI1/PU.1 related, JUN and TBP (By similarity). Expressed in the medulla of the thymus, the spleen and germinal centers of the lymph nodes. Expressed in B-cells and T-cells, expression increases during B-cell maturation and decreases during T-cell maturation. The protein contains a weakly acidic N-terminal transactivation domain (TAD) followed by a second TAD rich in proline, serine and threonine. Each of these domains may be required for transcriptional activation of a subset of target genes (By similarity). Produced by alternative promoter usage. Produced by alternative splicing of isoform IA. Produced by alternative promoter usage. Belongs to the ETS family.