Notch1-IC expression reduces the functional activity of pre-B cell-restricted promoter elements in a pre-B cell environment. The resulting relative luciferase activity when 2 μg λ5, B29, or Cd79a promoter-controlled reporter constructs were transiently transfected into the 230-238 pre-B cell line along with 1 or 3 μg Notch1-IC, as indicated. Reporter activities were normalized to the internal control CMV-Renilla and are presented relative to the value obtained after cotransfection of each respective reporter construct along with empty expression plasmid. The data are based on 6 transfection experiments and error bars indicate SD.