Using deletional promoter contructs (ff-luc) of human IL-16 promoter from ca. -3.3kb to +200, we found constitutive high levels of transcriptional activation in transfected Jurkat cells in constructs from -3.3kb to -1,000bp, consistent with the known consitutive high protein levels of IL-16 in resting T-cells. In contrast with known lack of IL-16 expression in unstimulated airway epithelial cells in vitro and in vivo, -2.2kb to -1,000bp constructs had high levels of transcriptional activation. High levels of activity were seen in -3.3Kb constructs in Jurkats, but NOT HBE4-E6/E7 cells (immortalized bronchial epithelial cells). We identified a putative repressor TRF consensus binding site (CBF-1/RBP-Jkappa, a CSL family protein) at ca. -2.3 kb upstream of transcriptional start site. We have preliminary data with EMSA that this site is bound in HBE4-E6/E7 nuclear extracts.
We would be interested in exploring the mechanism of differential transcription in epithelial vs. T-cells.