cyto receptors typically consist of two chains each having an extracellular cyto binding domain and an intracytoplasmic domain which binds a member of a family of protein tyrosine kinases called Janis kinases or Jacks in the absence of the cyto the two chains do not remain Associated cyto binding to the receptor stabilizes the heterodimer and brings together the Jacks that are bound to the cytoplasmic portions of each chain the Jack kinases are then able to phosphorate the cytoplasmic Tails of The cyto receptors signal transduction and transcription or Stat molecules bind to the phosphorated cyto receptor chains and are themselves phosphorated by the Jacks the addition of a phosphate to the stats enables them to dimerize and in this form migrate into the nucleus where they can directly activate Gene transcription