Recognizes the ribosomal RNA gene promoter and activates transcription mediated by RNA polymerase I through cooperative interactions with the transcription factor SL1/TIF-IB complex. It binds specifically to the upstream control element. Homodimer (By similarity). Interacts with TBP (By similarity). Interacts with TAF1A (By similarity). Interacts with RASL11A (PubMed:20168301). Binds to IRS1 and PIK3CA (PubMed:15197263). Interacts with DHX33 (PubMed:21930779). Interacts with PHF6 (By similarity). Interacts with CEBPA (isoform 1 and isoform 4) (By similarity). Interacts with DDX11 (By similarity). Interacts with NOP53 (By similarity). Interacts with ALKBH2. Phosphorylated and activated by PIK3CA.