Suppression of T cell function: a potential role for transcriptional repressor ICER

In this article, we review the inducible cAMP early repressor (ICER) and its possible critical involvement in modulation of T cell responsiveness by its capacity to transcriptionally attenuate interleukin-2 (IL-2) gene expression. It seems clear that the failure to produce the IL-2 is an important determinant of anergy induction. It is important that the CD28-responsive element (CD28RE), a composite DNA binding element consisting of NFAT and cyclic AMP-responsive (CRE)-like motifs in position of -160 of IL-2 promoter has the high affinity for ICER binding as well as NFAT/ICER complex formation. Moreover, CD28RE with adjacent DNA sequences was also shown to be essential for conferring anergy in T lymphocytes. Because ICER does not possess a transactivation domain required for the recruitment of CBP/p300, the binding of ICER to CD28RE and/or composite motifs containing CRE-like DNA motifs may lead to uncoupling of CBP/p300 thus extinguishing IL-2 expression as well as expression of numerous other cytokines and chemokines.