A novel element upstream of the Vγ2 gene in the murine T cell receptor γ locus cooperates with the 3' enhancer to act as a locus control region

Transgenic expression constructs were employed to identify a cis-acting transcription element in the T cell receptor (TCR)-γ locus, called HsA, between the Vγ5 and Vγ2 genes. In constructs lacking the previously defined enhancer (3'E(Cγ1), HsA supports transcription in mature but not immature T cells in a largely position-independent fashion. 3'E(Cγ1), without HsA, supports transcription in immature and mature T cells but is subject to severe position effects. Together, the two elements support expression in immature and mature T cells in a copy number-dependent, position-independent fashion. Furthermore, HsA was necessary for consistent rearrangement of transgenic recombination substrates. These data suggest that HsA provides chromatin-opening activity and, together with 3'E(Cγ1), constitutes a T cell-specific locus control region for the TCR-γ locus.