The pTalpha promoter and enhancer are direct targets for transactivation by E box-binding proteins.

The pre-Talpha (pTalpha[?]) gene encodes a protein that forms the pre-TCR together with the newly expressed TCR beta chain during a defined stage of early T cell development. The restricted expression of this gene has been suggested to depend on a promoter and an enhancer element containing E boxes, which are potential binding sites for basic helix-loop-helix (bHLH) proteins. We here report that increased expression of E47 and E12 mRNA in CD4(--)CD8(--)TCR(--) thymocytes correlates with the initiation of pTalpha[?] transcription. Furthermore, electrophoretic mobility shift assays suggested that E47 binds directly to both the pTalpha[?] promoter and enhancer in vitro. Ectopic expression of E47 in non-lymphoid HeLa cells resultedin a dose- and template-dependent activation of these control elements. In addition to this, ectopic expression of E47 in combination with the ets-protein Pu.1 and[?]/[?]or the Pu.1-interacting protein(Pip-1), resulted in a synergistic effect on the activity of the pTalpha[?] control elements. Thus, we suggest that E47, Pu.1 and Pip-1 are directly involved in the regulation of pTalpha expression inearly T cell development.