Interacts with the basal transcription machinery by coordinating the formation of a multiprotein complex at the C-FOS promoter, and linking specific signal responsive activator complexes. Promotes the formation of stable high-order complexes of SRF and PHOX1 and interacts cooperatively with PHOX1 to promote serum-inducible transcription of a reporter gene deriven by the C-FOS serum response element (SRE). Acts as a coregulator for USF1 by binding independently two promoter elements, a pyrimidine-rich initiator (Inr) and an upstream E-box. Required for the formation of functional ARID3A DNA-binding complexes and for activation of immunoglobulin heavy-chain transcription upon B-lymphocyte activation (By similarity). Homodimer (Potential). Interacts with SRF and PHOX1. Binds a pyrimidine-rich initiator (Inr) and a recognition site (E-box) for upstream stimulatory factor 1 (USF1). Associates with the PH domain of Bruton's tyrosine kinase (BTK). May be a component of a BHC histone deacetylase complex that contains HDAC1, HDAC2, HMG20B/BRAF35, KDM1A, RCOR1/CoREST, PHF21A/BHC80, ZMYM2, ZNF217, ZMYM3, GSE1 and GTF2I. Interacts with ARID3A. Interacts with isoform beta of PRKG1 (By similarity). Colocalizes with BTK in the cytoplasm. Transiently phosphorylated on tyrosine residues by BTK in response to B-cell receptor stimulation. Phosphorylation on Tyr-248 and Tyr-377, and perhaps, on Tyr-482 contributes to BTK-mediated transcriptional activation. Sumoylated. Belongs to the TFII-I family.