Posttranscriptional reduction of FECH in MEL cells during iron-limited differentiation. (A,C) Induction of FECH enzyme activity (red line), but not mRNA levels (blue, green lines), was repressed during differentiation in the presence of DFO. FECH mRNA levels were measured by quantitative RT-PCR as described in “Northern blots and quantitative RT-PCR analysis.” mRNA transcript and enzyme activity levels are normalized to T = 0 samples. (B,D) Induction of FECH protein levels during differentiation was attenuated in cells cotreated with DFO, despite increased FECH mRNA levels. FECH protein levels were measured by Western blot, and the filter was reprobed for SOD2 as a loading control for mitochondrial matrix proteins.