C/EBPβ and GATA-1 synergistically transactivate the MBP P2 promoter. Transactivation of the MBP promoter (bp −117/pXP2-MBP) in Jurkat cells, in which neither GATA-1 nor C/EBPβ transcription factors are expressed. The T-lymphocytic Jurkat cell line was transfected by the electroporation method with 5 μg of the MBP promoter construct (bp −117/pXP2-MBP) along with the following expression constructs: pXP2-MBP + pEF-BOS, pXP2-MBP (control) and 4 μg of pEF-BOS (the control plasmid containing the elongation factor promoter without cDNAs); pXP2-MBP + pEF-GATA1, 2 μg of pEF-GATA-1, and 2 μg of pEF-BOS; pXP2-MBP + pEF-C/EBPβ; 2 μg of pEF-C/EBPβ and 2 μg of pEF-BOS, pXP2-MBP + pEF-GATA-1 + pEF-C/EBPβ; and 2 μg of pEF-GATA-1 and 2 μg of pEF-C/EBPβ. Luciferase activity was measured 24 hours after transfection and normalized for transfection efficiency based on the activity of a cotransfected β-galactosidase expression vector (CMV-βGal). Data are shown as the mean of 3 independent experiments (±SEM).