Fig. 4. Schematic diagram of regulatory and structural regions of a steroid hormone responsive gene. Located upstream from the transcription start site are several regulatory cis-acting elements that interact with various factors, including steroid hormone receptors that bind to hormone response elements, C/EBP that binds to CCAAT boxes,232 and Sp1 that binds to GC boxes.233 TFIID and the other general transcription factors bind to the TATA box to control transcription of the target gene.39 The structural region of the gene contains nucleotides encoding the mRNA transcript that will be translated into the protein. (Adapted from Tsai M-J, O'Malley BW: Molecular mechanisms of action of steroid/thyroid receptor superfamily members. Annu Rev Biochem 63:451–483, 1994.)