Identification and functional analysis of the transcriptional enhancer of the human T cell receptor beta gene.

The productive rearrangement and transcription of T cell receptor (TcR) beta genes is confined to T lymphocytes and is subject to both tissue-specific and developmental regulation. In addition to their function in transcriptional control, cis-acting elements are likely to play a role in the regulation of the rearrangement process. In this report we describe the location of a strong and inducible transcriptional enhancer 3' to the human TcR C beta 2 gene segment. The core enhancer, defined by deletion analysis using a transient transfection assay, resided within 362 bp of DNA. This enhancer core was able to activate transcription from a heterologous promoter and functioned well in T and B lymphocytes, but only minimally in HeLa cells. In contrast, a longer fragment containing the enhancer core showed marked T cell specificity. The enhancer was highly inducible by phorbol esters, the molecular basis for the inducibility residing within a 118-bp region of the enhancer core. This inducibility may be important in modulation of TcR beta gene expression during T cell differentiation and/or activation.