Cyclin D3 silencing mimics l-Arg starvation effects on cell cycle. (A) Wild-type Jurkat cells (Jurkat) and Jurkat cells transfected with empty vector, nonrelated human sequence, or sh–cyclin D3 plasmid were tested for the expression of cyclin D3 RNA by Northern blot and cyclin D3 protein by Western blot. (B) Wild-type Jurkat cells or transfected cells were cultured in the presence or the absence of l-Arg and tested for proliferation after 48 hours by [3H]-thymidine incorporation.