Coordinate Post-Transcriptional Regulation of Ferritin and Transferrin Receptor Expression: The Role of Regulated RNA-Protein Interaction
Two of the best understood examples of post-transcriptional gene regulation in eukaryotic cells have emerged from studies on cellular iron metabolism. Although assimilation and metabolism of iron by higher eukaryotes is a complex process about which many unanswered questions remain (Seligman et al., 1987), some progress has been made in the understanding of iron uptake and sequestration by individual eukaryotic cells (Klausner & Harford, 1990; Theil, 1990; Harford et al., 1990). Iron is delivered to most cells via the “transferrin cycle” involving endocytosis of the iron-carrying protein transferrin (Tf). This endocytic pathway is mediated by the transferrin receptor (TfR). From an acidic endosome, iron is released from Tf and transferred by unknown means to the cytoplasm. Once in the cytoplasm, the iron is utilized for the many cellular processes that require iron or it is sequestered into ferritin, a hollow, spherical molecule composed of 24 subunits encoded by two homologous genes (termed H and L) (Munro & Linder, 1978; Theil, 1987). Presumably, this sequestration is largely responsible for the detoxification of unused iron.
KeywordsCodon Cysteine Assimilation Disulfide NADPH
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