Sp1 transactivates the Dlk2 promoter. NIH3T3 cells were transiently transfected with A) pGL3Basic(-212/+1), pGL3Basic(-375/+1), pGL3Basic(-375/+1Δ), pGL3Basic(+1/+177), or pGL3Basic(-212/+177); or B) pGL3Basic(-212/+1), pGL3Basic(-212/+1M1), pGL3Basic(-212/+1M2), pGL3Basic(-212/+1M3), pGL3Basic(+1/+177), pGL3Basic(+1/+177M4), pGL3Basic(+1/+177M5), or pGL3Basic(+1/+177M6), along with either pCMVSport (control) or pCMVSport-Sp1, to drive the overexpression of Sp1. A Sp1 luciferase-reporter plasmid was used as a control of Sp1 activity. Luciferase activities were measured 24 hours after transfection. In each transfection, luciferase values were normalized to the corresponding Renilla values, as previously described. The average values of at least three independent experiments are shown. (*, ** and ***, significant versus control in Student's t-test with p-values < 0.05, < 0.01 and < 0.001, respectively).