THE HIGH-MOBILITY GROUP TRANSCRIPTION FACTOR, SOX4, TRANSACTIVATES THE HUMAN CD2 ENHANCER

A strong T cell-specific enhancer is located 3' to the human CD2 gene, Six sequences within this enhancer are bound by proteins present in T cell nuclear extracts, These sequences share homology with sequences bound by several transcription factors involved in T cell- and lymphoid-specific transcription, The results presented here demonstrate that the human T cell-specific transcription factor, SOX4, is able to bind to one of these regions; further, SOX4 transactivates transcription of a reporter gene via three tandem copies of this sequence, The binding of SOX4 to this site is not via a canonical HMG protein binding sequence, identifying a novel class of binding site for this protein, A second sequence within the CD2 enhancer closely resembles the IL-2 NF-AT site, We show that it is bound by the ets-related factor, Elf1. However, unlike the IL-2 NF-AT sequence, the CD2 NF-AT like sequence is unable to confer transcriptional inducibility on a reporter gene, Consistent with this result, we show that the observed increase in expression of CD2 protein on the cell surface following T cell activation is a post-transcriptional event.