Cyclin D1 protein expression is higher and persists longer after inhibition with actinomycin D in cells expressing a truncated cyclin D1a transcript than in cells expressing a normal cyclin D1a transcript. Western blots of cyclin D1 protein expression in KMS-12 (normal cyclin D1a transcript) and Z-138 cells (truncated cyclin D1a transcript) treated with actinomycin D for the indicated time points. Antibodies against alpha tubulin (loading control at 55 kDa) and cyclin D1 (38 kDa) were used simultaneously. Vehicle (dimethyl sulfoxide [DMSO]) only treated cells at 12 hours are included as control (far right lane).