Ferritin repression in HeLa cells transfected with siRNAs. HeLa cells were transfected with various amounts of 4 different H-siRNAs (A) and 4 different L-siRNAs (B) (described in “Materials and methods”), harvested 40 hours later, and analyzed for ferritin content by ELISA specific for H-ferritin (A) and L-ferritin (B). (C) Time course analysis of ferritin expression of HeLa cells transfected with 1.6 μg H-siRNA (oligo 3). As shown in the insert, the cell homogenates (20 μg total proteins) were loaded on 12% SDS-PAGE for the indicated time and immunoblotted with a monoclonal anti–H-ferritin subunit antibody (HS-59). Representative of 3 independent experiments with similar results.