Fig. 5. Delineation of the OLIG2-responsive region of the human p27^Kip1 gene promoter. (A) Schematic representation of luciferase reporter plasmids containing a series of 5' deletion mutants of the human p27^Kip1 gene promoter. Nucleotide numbers are relative to the transcription start site. (B) Luciferase activities of U12-1 cells transfected with the indicated reporter plasmids and cultured in Tet-on or Tet-off medium. The experimental reporter luciferase activity was calculated by subtracting the intrinsic activity as measured by samples corresponding to pGVB2, and then normalized by that of Renilla luciferase encoded by the cotransfected pRL-TK. Data are means ± s.d. of values from at least three independent experiments. ^*P<0.05, ^**P<0.01 (Student's t-test).