Binds a variety of cellular and viral promoters including fibrinogen; alpha-globin; SV40 and HIV-1 promoters. Activation of the alpha-globin promoter in erythroid cells is via synergistic interaction with UBP1 (By similarity). Functions as part of the SSP (stage selector protein) complex. Facilitates the interaction of the gamma-globin genes with enhancer elements contained in the locus control region in fetal erythroid cells. Interacts by binding to the stage selector element (SSE) in the proximal gamma-globin promoter. {ECO:0000250; ECO:0000269|PubMed:10455131; ECO:0000269|PubMed:1732747; ECO:0000269|PubMed:8035790; ECO:0000269|PubMed:8157699}.