Signal Transducer and Activator of Transcription Family Genes encode dual function cytoplasmic Signal Transducer and Activator of Transcription (STAT) proteins that are activated by tyrosine phosphorylation in response to a large number of cytokines, growth factors, and hormones. After activation they form homodimers or heterodimers that translocate to the nucleus where they either bind directly to regulatory DNA cis-elements of specific target genes or act together with other DNA-binding proteins in multiprotein transcription complexes to direct transcription. (NCI) [ ]