Cytoplasmic protein binds in vitro to a highly conserved sequence in the 5' untranslated region of ferritin heavy- and light-subunit mRNAs.

TLDR

Ferritin heavy‑ and light‑subunit mRNAs exist mainly as inactive ribonucleoprotein particles that are recruited for translation upon iron entry into cells. The study proposes that intracellular iron levels regulate ferritin synthesis by modulating specific protein binding to a conserved sequence in the ferritin mRNAs. Electrophoretic and UV cross‑linking analyses revealed that cytoplasmic extracts form iron‑responsive RNA‑protein complexes with the conserved 5′‑UTR of ferritin mRNAs, involving an 87‑kDa protein whose binding pattern changes with iron pretreatment.

Abstract

The mRNAs for the heavy and light subunits of the iron-storage protein ferritin occur in cells largely as inactive ribonucleoprotein particles, which are recruited for translation when iron enters the cell. Cytoplasmic extracts from rat tissues and hepatoma cells were shown by an electrophoretic separation procedure to form RNA-protein complexes involving a highly conserved sequence in the 5' untranslated region of both ferritin heavy- and light-subunit mRNAs. The pattern of complex formation was affected by pretreatment of rats or cells with iron. Crosslinking by UV irradiation showed that the complexes contained an 87-kDa protein interacting with the conserved sequence of the ferritin mRNA. We propose that intracellular iron levels regulate ferritin synthesis by causing changes in specific protein binding to the conserved sequence in the ferritin heavy- and light-subunit mRNAs.