Interleukin 2 receptor signaling regulates the perforin gene through signal transducer and activator of transcription (Stat)5 activation of two enhancers

Optimal T cell differentiation into effector cells with specialized functio ns requires the participation of cytokine receptor signals. In T helper cel ls, this process is controlled by chromatin changes and distal and proximal regulatory elements as well as specific transcription factors. Analogous e vents during cytotoxic T lymphocyte (CTL) differentiation remain to be iden tified. This process is known, however, to be crucially regulated by interl eukin (IL)-2 receptor (R) signals. It is accompanied by the induction of pe rforin expression via a mechanism that does not entail proximal regulatory elements. In this report, transgenically expressed human perforin gene locu s DNAs demonstrate that IL-2R signals target two IL-a-dependent enhancers s imilar to 15 and 1 kilobase upstream of the promoter. The most distal enhan cer may also respond to TCR signals. In transient transfections, both enhan cers required two identically spaced Stat-like elements for their activatio n, which was abolished by expression of a dominant negative signal transduc er and activator of transcription (Stat)5 molecule, whereas a constitutivel y active Stat5 molecule bypassed the requirement for IL-2R signals. These r esults provide a molecular explanation for the activation of the perforin g ene during CTL differentiation and complement the analysis of animals defic ient in the activation of the IL-2R Stat signaling pathway by establishing perforin as a target gene.