Effect of ATRA on the expression of the FR-β transcript.

(A) KG-1 cells were treated with ATRA (1 μmol/L), PMA (0.05 μmol/L), or the vehicle alone for 5 days. The total RNA was purified and probed on a Northern blot with cDNA for FR-β, FR-α, or γ-actin. (B) KG-1 cells were treated with ATRA (1 μmol/L) for 6 hours. Nuclei were isolated and nuclear run-on reactions carried out as described in “Materials and methods.” Labeled RNA isolated from each reaction was used to probe immobilized cDNA for FR-β or γ-actin as described in “Materials and methods.”