Practice question

Ferritin mRNAs contain iron responsive element IRE conserved hairpin in 5' UTR regulating translation via iron regulatory proteins IRP1 and IRP2. Low iron allows IRP binding blocking 43S scanning and 60S joining repressing synthesis. IRP1 holds Fe-S cluster converting to aconitase when iron sufficient; IRP2 degraded via FBXL5 sensing iron. High iron causes IRP dissociation permitting ferritin production storing iron in mineral core preventing Fenton reactions generating reactive oxygen species. This translational control complements transferrin receptor regulation via 3' UTR IREs stabilizing transcript when iron scarce, coordinating iron uptake, storage, and utilization balancing cellular needs.