Effects of ATRA on PML-RARα– and PLZF-RARα–induced elevation of cyclin A1 in inducibly transfected U937 cells.

(A) PR9 cells were induced to express PML-RARα for 24 hours, and expression of cyclin A1 mRNA was analyzed by Northern blot at various time points after addition of ATRA (1 μmol/L). On each lane, 20 μg total RNA was loaded. (B) Dose-effect of ATRA (24 hours) was analyzed as in panel A. (C) Real-time PCR was used to compare the dose-dependent effects of ATRA on PML-RARα– and on PLZF-RARα–expressing U937 cells (see “Materials and methods” for details on the procedure). Shown are means and SEM of 3 independent analyses. At all concentrations of ATRA, the effects on cyclin A1 expression were more pronounced in PML-RARα– than in PLZF-RARα–expressing cells.