Cell culture and transfection.
GM979 cells (Coriell Cell Repositories, Camden, New Jersey, United States) were cultured in Ham's F12 with 2 mM L-glutamine supplemented with heat-inactivated 10% fetal calf serum (Ivitrogen, Carlsbad, California, United States), penicillin (100 units/ml), streptomycin 100 μg/ml), and L-glutamine (2 mM). MEL cells were cultured in DMEM supplemented as above (without heat inactivating the serum). GM979 cells (4 × 105) in log phase of growth were transfected with plasmids by FuGENE6 (Roche, Indianapolis, Indiana, United States). Cells were transfected with ɛy promoter reporter constructs (500 ng) along with either empty vector or Sox6 overexpression vector (1000 ng). In assays of dosage effect, we used 200 ng, 500 ng, and 1000 ng). pRL-CMV 15ng (Promega) was used as a control for transfection efficiency.