Nuclear extracts from Daudi and SK-N cells were isolated using NE-PER Nuclear and Cytoplasmic Extraction Reagents (38) from Pierce Biotechnology following the manufacturer's instruction. Western blotting was performed using 20 mg of nuclear extracts. After separation on a 10% SDS-PAGE gel, the proteins were transferred to a nitrocellulose membrane and probed with anti-human SF2/ASF antibody [1:200 dilution, goat polyclonal immunoglobulin G (IgG; Santa Cruz Biotechnology] followed by washing in 2% milk-PBS Tween. The membrane was then incubated with Donkey anti-goat IgG (1:5000 dilution; horseradish peroxidase-conjugated (BD Biosciences) and followed by washing again. Substrates, luminal and enhancer were added onto the membrane and incubated for 1 min. The membrane was exposed to Kodak XAR-5 film with intensifying screens for 5 min. Anti-human b-actin antibody (1:6000 dilution, goat monoclonal IgG; BD Biosciences) was used as loading controls. The exposure time for b-actin was 20 s.