Transcription factor; part of the gene cluster that mediates the biosynthesis of sterigmatocystin (ST), a polyketide-derived furanocoumarin which is part of the most toxic and carcinogenic compounds among the known mycotoxins (PubMed:8643646, PubMed:8662194). Binds to the palindromic sequence 5'-TCG(N5)CGA-3'found in the promoter regions of several sterigmatocystin cluster genes to induce their expression (PubMed:9680223). Mycotoxin biosynthesis; sterigmatocystin biosynthesis [regulation]. Imeairs expression of the sterigmatocystin cluster genes.