Signal transducer and activator of transcription (Stat) binding toDNA. In this two-dimensional model, the heterodimerized or homodimerized Statmolecule binds to the appropriate DNA sequence via a 'C clamp'structure. Note that in addition to the specificity controlled by the DNAbinding domain, other regions of the Stat molecule may also be important in DNAinteractions. Tetramerization of the Stats may allow for an even greater degreeof stability in DNA binding to adjacent imperfect Stat binding sites; this ismediated by the Stat amino-terminus (not shown). Also not shown in thisillustration is the Stat transcriptional activation domain.