Functional analysis of the murine TCR beta-chain gene enhancer

The TCR beta-chain gene enhancer activates transcription and V(D)J recombin ation in immature thymocytes, In this paper we present a systematic analysi s of the elements that contribute to the activity of the murine TCR beta en hancer in mature and immature T cell lines. We identified a region containi ng the beta E4, beta E5, and beta E6 motifs as the essential core of the TC R beta enhancer in pro-T cells. In mature cells, the core enhancer had low activity and required, in addition, either 5' or 3' flanking sequences whos e functions may be partially overlapping, Mutation of any of the six protei n binding sites located within the beta E4-beta E6 elements essentially abo lished enhancer activity, indicating that this core enhancer contained no r edundant elements. The beta E4 and beta E6 elements contain binding sites f or ETS-domain proteins and the core binding factor. The beta E5 element bou nd two proteins that could be resolved chromatographically and that were bo th essential for enhancer activity.