Regulation of IRE-containing mRNAs by HFE expression. Ferritin (molecular weight, 19/21 kD), transferrin receptor (94 kD), U1A (32 kD), and HFE (43/47 kD) were immunoprecipitated from extracts of doxycycline-untreated (−) or -treated (+) cells, respectively. Precipitated proteins were seperated by SDS-PAGE and quantitated by phosphorimaging. The amounts of proteins immunoprecipitated from cells not treated with doxycycline were set to 100%.