A Developmental Stage-Specific Promoter Directs Germline Transcription of DβJβ Gene Segments in Precursor T Lymphocytes

The tissue- and stage-specific assembly of Ag receptor genes is regulated by transcriptional control elements positioned within Ig and TCR loci. To further understand the role of cis-acting elements in these regulatory mechanisms, we have characterized a transcriptional promoter that drives germline expression of TCRβ gene segments in vivo. The activity of this promoter, termed PDβ, is restricted to a highly conserved 400-bp region located directly upstream from Dβ1-coding sequences. Maximal PDβ activity requires a TATA element situated within the Dβ1 recombination signal sequences and consensus binding sites for the ubiquitous SP1 and the T cell-specific GATA-3 transcription factors. When linked to active enhancer elements, PDβ directs transcription in most cell types; however, the TCRβ enhancer (Eβ) stimulates PDβ function specifically in precursor T lymphocytes. These findings suggest that PDβ/Eβ interactions may contribute to differential regulation of regions within the TCRβ locus during thymocyte development.