Repression of IL-2 promoter activity by the novel basic leucine zipper p21(SNFT) protein

IL-2 is the major autocrine and paracrine growth factor produced by T cells upon T cell stimulation. The inducible expression of IL-2 is highly regula ted by multiple transcription factors, particularly AP-1, which coordinatel y activate the promoter. Described here is the ability of the novel basic l eucine zipper protein p21(SNFT) to repress AP-1 activity and IL-2 transcrip tion. A detailed analysis of the repression by p21(SNFT) repression on the IL-2 promoter distal NF-AT/AP-1 site demonstrates that it can bind DNA with NF-AT and Jun, strongly suggesting that it represses NF-AT/AP-1 activity b y competing with Fos proteins for Jun dimerization, The importance of this repression is that p21(SNFT) inhibits the trans-activation potential of pro tein complexes that contain Jun, thereby demonstrating an additional level of control for the highly regulated, ubiquitous AP-1 transcription factor a nd the IL-2 gene.