In iron deficiency, iron regulatory proteins (IRP1 and IRP2) bind iron response elements (IREs) on specific mRNAs. What is the combined effect of this binding on ferritin and the transferrin receptor?

• A Ferritin synthesis increased, transferrin receptor synthesis decreased
• B Both ferritin and transferrin receptor synthesis increased
• C Ferritin synthesis decreased, transferrin receptor synthesis increased ✓
• D Both ferritin and transferrin receptor mRNA degraded

Explanation

When cellular iron is scarce, IRPs bind the IRE in the 5' untranslated region of ferritin mRNA and sterically block ribosome assembly, suppressing ferritin translation. They also bind IREs clustered in the 3' untranslated region of transferrin receptor mRNA, protecting it from endonucleolytic degradation and increasing receptor synthesis. When iron is plentiful, IRP1 assembles a 4Fe-4S cluster, becomes cytosolic aconitase, releases the IREs, and the pattern reverses.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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