Deletion analysis of the type 2 CD10/NEP promoter. (Left) CD10/NEPpXP₂ deletion constructs. Deletion constructs containing progressively shorter segments of the type 2 CD10/NEP promoter in the promoterless luciferase vector pXP₂ are shown. Positions of the indicated constructs are relative to the major initiation of transcription site (). (Right) Luciferase assays of CD10/NEPpXP₂ deletion constructs. The resulting CD10/NEPpXP₂ constructs and CMV-GH internal controls were cotransfected into Nalm-6 cells and FHTE56 cells to analyze CD10/NEP-driven luciferase activity. In all assays, luciferase activity was normalized for transfection efficiency by evaluating supernatants from the transient transfections for simultaneous GH secretion (ng GH secretion/mL supernatant). Promoter activity (RLUs) and % maximum CD10/NEP-driven activity represent the mean ± SE for two separate experiments performed in triplicate: FHTE56 v, Nalm-: −263/+147, 742 (100%) v 639 (100%); −208/+147, 709(95% ± 5%) v 621(98% ± 3%); −175/+105, 538(71% ± 3%) v 554(80% ± 7%); −1151/+105, 210(27% ± 2%) v 519(75% ± 7%); P < .001. pXP₂ alone, 66 v 35, respectively. The differences in CD10/NEP-driven luciferase activity of CD10/NEP(−115/+105)pXP₂ in FHTE56 and Nalm-6 cells were analyzed using a one-sided Student's t-test.