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 mim ic antigen stimulation through the T-cell receptor. We have previously shown that a fragment containing bp -95 to +27 of the mouse GM-CSF pr omoter can confer inducibility to reporter genes in the human Jurkat T -cell line. Here we use an in vitro transcription system to demonstrat e that a cis-acting element (positions -54 to -40), referred to as CLE O, is a target for the induction signals. We observed induction with t emplates containing intact CLEO but not with templates with deleted or mutated CLEO. We also observed that two distinct signals were require d for the stimulation through CLEO, since only extracts from cells tre ated 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 transc ription. One of the binding factors possessed biochemical and immunolo gical features identical to those of the transcription factor A.Pl. An other factor resembled the T-cell-specific factor NFAT. The characteri stics 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 tha t recognize these sites, may account for the coordinate induction of t hese genes during T-cell activation.