) ▁ ▁Type ▁I ▁inter fer ons ▁( IF N - a , ▁IF N - b ) ▁bind ▁to ▁re cept ors , ▁cause ▁signal ing ▁via ▁kin ases , ▁ph osph ory late ▁and ▁activ ate ▁the ▁Jak ▁kin ases ▁T Y K 2 ▁and ▁J AK 1 ▁and ▁also ▁ST AT 1 ▁and ▁ST AT 2 . ▁ST AT ▁mole cules ▁form ▁dim ers ▁and ▁bind ▁to ▁IS G F 3 G / IR F - 9 , ▁which ▁is ▁Inter fer on ▁stim ulated ▁gene ▁factor ▁ 3 ▁complex ▁with ▁Inter fer on ▁regul atory ▁F actor ▁ 9 . ▁This ▁allows ▁ST AT 1 ▁to ▁enter ▁the ▁nucle us . ▁ST AT 1 ▁has ▁a ▁key ▁role ▁in ▁many ▁gene ▁expressions ▁that ▁cause ▁surv ival ▁of ▁the ▁cell , ▁vi ability ▁or ▁path ogen ▁response . ▁There ▁are ▁two ▁possible ▁trans cript s ▁( due ▁to ▁alternative ▁sp lic ing ) ▁that ▁encode ▁ 2 ▁is o forms ▁of ▁ST AT 1 ▁ ▁ST AT 1 ▁is ▁involved ▁in ▁up reg ulating ▁gen es ▁due ▁to ▁a ▁signal ▁by ▁either ▁type ▁I , ▁type ▁II , ▁or ▁type ▁III ▁inter fer ons . ▁ ▁In ▁response ▁to ▁IF N - γ ▁stim ulation , ▁ST AT 1 ▁forms ▁hom od im ers ▁or ▁heter od im ers ▁with ▁ST AT 3 ▁that ▁bind ▁to ▁the ▁G AS ▁( Inter fer on - Gamma - Activ ated ▁Se quence ) ▁prom oter ▁element ; ▁in ▁response ▁to ▁either ▁IF