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. May be 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. Expressed in plasmacytoid dendritic cells (pDCs) and B-cells, not expressed in T-cells or granulocytes. May also be enriched in stem cell populations of the liver. 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. Belongs to the ETS family.