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Functional Analysis of the Murine TCRβ-Chain Gene Enhancer1

The TCRβ-chain gene enhancer activates transcription and V(D)J recombination in immature thymocytes. In this paper we present a systematic analysis of the elements that contribute to the activity of the murine TCRβ enhancer in mature and immature T cell lines. We identified a region containing the βE4, βE5, and βE6 motifs as the essential core of the TCRβ enhancer in pro-T cells. In mature cells, the core enhancer had low activity and required, in addition, either 5′ or 3′ flanking sequences whose functions may be partially overlapping. Mutation of any of the six protein binding sites located within the βE4–βE6 elements essentially abolished enhancer activity, indicating that this core enhancer contained no redundant elements. The βE4 and βE6 elements contain binding sites for ETS-domain proteins and the core binding factor. The βE5 element bound two proteins that could be resolved chromatographically and that were both essential for enhancer activity.