FIG. 3.

Transcriptional activity of the IB1 promoter region. The region of the IB1 promoter comprising bp −691 to + 41 (IB1LUC) drove a high luciferase activity in the insulin-secreting βTC3, INS1, and PC12 cells (13-, 11-, and 18-fold higher, respectively, than that for the promoterless vector pGL3 basic) but not in unrelated HeLa, NIH 3T3, Jurkat, and RAW cells. Each experiment was repeated at least three times in triplicate. Luciferase activities were normalized using pRLCMVrenilla, and results are expressed as means ± standard errors of the means (triple asterisk, P < 0.001).