THE GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR PROMOTER CIS-ACTING ELEMENT CLE0 MEDIATES INDUCTION SIGNALS IN T-CELLS AND IS RECOGNIZED BY FACTORS RELATED TO AP1 AND NFAT

Expression of the granulocyte-macrophage colony-stimulating factor (GM-CSF) gene in T cells is activated by the combination of phorbol ester (phorbol myristate acetate) and calcium ionophore (A23187), which mimic antigen stimulation through the T-cell receptor. We have previously shown that a fragment containing bp -95 to +27 of the mouse GM-CSF promoter can confer inducibility to reporter genes in the human Jurkat T-cell line. Here we use an in vitro transcription system to demonstrate that a cis-acting element (positions -54 to -40), referred to as CLEO, is a target for the induction signals. We observed induction with templates containing intact CLEO but not with templates with deleted or mutated CLEO. We also observed that two distinct signals were required for the stimulation through CLEO, since only extracts from cells treated with both phorbol myristate acetate and A23187 supported optimal induction. Stimulation probably was mediated by CLEO-binding proteins because depletion of these proteins specifically reduced GM-CSF transcription. One of the binding factors possessed biochemical and immunological features identical to those of the transcription factor A.Pl. Another factor resembled the T-cell-specific factor NFAT. The characteristics of these two factors are consistent with their involvement in GM-CSF induction. The presence of CLE0-like elements in the promoters of interleukin-3 (IL-3), IL-4, IL-5, GM-CSF, and NFAT sites in the IL-2 promoter suggests that the factors we detected, or related factors that recognize these sites, may account for the coordinate induction of these genes during T-cell activation.