A, Tst-1/Oct6/SCIP transactivates the β4 gene promoter in a cell type-specific manner. The β4/luciferase construct pX1B4FH was transfected into neuronal cell lines (Neuro2A and SN17) and non-neuronal cell lines (Sol8 muscle and NIH3T3 fibroblast) either alone (−) or with pCMV5 (pCMV) or pCGS-SCIP (SCIP). Fold induction was calculated as described in Figure 3. B, C, Tst-1/Oct6/SCIP and Sox10 do not transactivate the β4 or α3 gene promoters additively or synergistically. SN17 cells were transfected with the β4/luciferase construct pX1B4FH (B) or the α3/luciferase construct pX1A3HS (C) either alone (−), with pCMV5 (pCMV), or with expression constructs for Sox10 and Tst-1/Oct6/SCIP (SCIP) individually and together. Fold induction was calculated as described above.