New protein synthesis is not required for BCL3upregulation by IL-9. BW5147 cells were stimulated with 100 U/mL IL-9 and with or without the combination of 10 μg/mL cycloheximide and 50 μmol/L MG-132 (a proteasome inhibitor) for 4.5 hours, or the cells were left unstimulated. Total RNA was extracted and RT-PCR amplification was performed with oligonucleotides specific forBCL3 or β-actin. A Southern blot of the PCR products was performed and filters were hybridized with the BCL3 orβ-actin cDNA probes.