Peg-Arg I inhibits the expression of cyclin D3 in T-ALL cells through a global arrest in protein synthesis. (A) Cyclin D3 mRNA levels were tested by RT-PCR in CCRF-CEM cells cultured for 24 hours in medium with or without L-Arginine (L-Arg) or in medium containing increasing concentrations of peg-Arg I (0.5-3 IU/mL). (B) Pulse-chase analysis for cyclin D3 in CCRF-CEM cells cultured in the presence or the absence of peg-Arg I (2 IU/mL) for 24 hours. (C) Cyclin D3 mRNA levels were tested in polysomes isolated using sucrose gradients from CCRF-CEM cells cultured in RPMI with or without peg-Arg I for 24 hours. (D) A representative experiment from panel C, in which fractions were tested for absorbance (260 nm) to determine the general distribution of the polysomes. (E) CCRF-CEM cells cultured in medium with peg-Arg I (2 IU/mL) were tested for the expression of phospho-eIF2α by immunoblot. The experiments were repeated a minimum of 3 times obtaining similar results.