STAT3 (Signal Transducer and Activator of Transcription 3) is one of seven of a family of homologous STAT proteins that differentially regulate gene expression. STAT 3 is important in both the development of embryos and many functions in adult organisms. [1] 
  Structure 
The STAT3 protein is composed of several helix-turn-helix structures and its quaternary structure consists of two STAT3 proteins dimerized with themselves. [2] There is a  at the C-terminal that plays a large role in transcriptional activation during regulatory events. 
  Regulation 
  DNA-Protein Interactions 
The  by binding to the major groove of the DNA.