Identification of a Novel, Spliced Variant of CREB That Is Preferentially Expressed in the Thymus

A conserved decamer sequence, AGTGA(T/C)(G/A)TCA, related to the cAMP response element (CRE), is found in the promoter regions of most TCR Vβ gene segments. It has been shown to be a critical element for T cell-specific transcriptional regulation of the TCR genes. However, none of the decamer or CRE-binding proteins identified thus far is restricted in its expression to cells of the T cell lineage. Therefore, to find T cell-restricted decamer-binding proteins, we screened thymus cDNA expression libraries using the decamer probe. One of the thymus cDNAs identified, clone pmLY2, a novel spliced variant of CREB, was shown to be preferentially expressed in thymus. Therefore, clone pmLY2 is the first T cell-enriched decamer-binding sequence identified. We hypothesize that this CREB variant may play a role in the developmental regulation of TCR and of other T cell specific genes.