ETS1, NF-KAPPA-B AND AP1 SYNERGISTICALLY TRANSACTIVATE THE HUMAN GM-CSF PROMOTER

Activation of helper T cells results in coordinate expression of a num ber of cytokines involved in differentiation, proliferation and activa tion of the haematopoietic system, Granulocyte-macrophage colony stimu lating factor (GM-CSF) is one such cytokine, whose increased expressio n results mostly from increases in transcription, Cis-acting elements with NF kappa B, AP1 and ETS-like binding motifs have been identified in the promoter region of the GM-CSF gene, and are important or essent ial for transcriptional activity following T cell activation, ETS1 is a transcription factor of the ETS family that is expressed in T cells, We have previously shown that ETS1 can transactivate GM-CSF in Jurkat T cells, but only after the cells have been stimulated by treatment w ith PMA and ionomycin, agents that mimic T cell activation, Thus we pr oposed that ETS1, which is expressed constitutively in Jurkat cells, m ay act in concert with PMA/ionomycin inducible factors, Here we show t hat ETS1 can transactivate a GM-CSF reporter construct in unstimulated Jurkat cells, providing that either NF kappa B or AP1 transcription f actors are supplied by co-transfection, We confirm that binding of end ogenous NF kappa B and AP1 is induced following PMA/ionomycin treatmen t of T cells, Transactivation by ETS1, NF kappa B and AP1 is synergist ic, and mutation of the individual binding sites reveals that the tran scriptional activities of these factors are interdependent, Our result s suggest that constitutive ETS1, and inducible NF kappa B and AP1, co operate as part of a higher order transcriptional complex in activated T cells.