Structural requirements of iron-responsive elements for binding of the protein involved in both transferrin receptor and ferritin mRNA post-transcriptional regulation.
The synthesis of both transferrin receptor (TfR) and ferritin is regulated post-transcriptionally by iron. This is mediated by iron responsive elements (IREs) in the 5'- and 3'-untranslated regions, respectively, of TfR and ferritin mRNAs. Although these IREs have different sequences, they both form a characteristic stem-loop. We used competition assays and partial peptide mapping of UV-crosslinked ferritin and TfR IRE-protein complexes to show that the cytosolic protein binding to the ferritin 5'-IRE, the iron-responsive element binding protein (IRE-BP), also binds to TfR 3'-IREs. To identify the structural requirements necessary for RNA-protein binding, ferritin IRE RNAs were synthesized which contained altered secondary structures and base substitutions. Affinities of these RNAs for IRE-BP were assayed in RNA-protein binding gels. Substitutions disrupting base-pairing of the stem prevented IRE-BP binding. Substitutions which restored base-pairing also restored IRE-BP binding. We conclude that the IRE-BP binds to both ferritin and TfR IREs and recognizes a particular IRE conformation.
Leibold
E A
EA
Department of Medicine, University of Utah School of Medicine, Salt Lake City 84132.
Laudano
A
A
Yu
Y
Y
D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D005293:Ferritins / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects; D007501:Iron / Q000494:pharmacology*; D008099:Liver / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D012323:RNA Processing, Post-Transcriptional / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics*; D051381:Rats; D011919:Rats, Inbred Strains; D011990:Receptors, Transferrin / Q000235:genetics*; D014158:Transcription, Genetic
D002352:Carrier Proteins; D012333:RNA, Messenger; D011990:Receptors, Transferrin; D005293:Ferritins; D007501:Iron