Optimal sequence and structure of iron-responsive elements. Selection of RNA stem-loops with high affinity for iron regulatory factor.
Optimal sequence and structure of iron-responsive elements. Selection of RNA stem-loops with high affinity for iron regulatory factor.
复制标题
铁反应元件的最佳序列和结构。
DOI：
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发表时间：
1994
期刊：
影响因子：
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通讯作者：
Lukas C. KuhnS
中科院分区：
文献类型：
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作者：
B. Henderson;E. Menotti;C. Bonnard;Lukas C. KuhnS
Iron regulatory factor (IRF) is a cytoplasmic mRNA-binding protein with specificity for iron-responsive element (IRE) RNA stem-loops. IRF post-transcriptionally regulates intracellular iron levels via binding to IREs in the untranslated regions of ferritin, transferrin receptor, and erythroid 5-aminolevulinic-acid synthase mRNAs. Specific IRE nucleotides are phylogenetically conserved: those of the 6-base loop (5'-CAGUGN-3') and an unpaired "bulge" cytosine. We prepared a pool of 16,384 IRE molecules randomized at these seven nucleotide positions and employed in vitro selection to identify RNAs that bind human IRF. Two major classes of high affinity RNA ligands were selected; the optimal loop sequences of each are 5'-CAGUGN-3' (wild type) and 5'-UAGUAN-3'. This novel finding predicts base pairing within the IRE loop between positions 1 and 5, thus facilitating the formation of a specific loop structure in which nucleotides at positions 2-4 are made accessible for protein interaction. Nucleotide substitution at these loop positions, or at the position of the bulge cytosine, decreased binding by 36-99%. In addition, we demonstrate a preferred IRE bulge structure and report a striking difference in the RNA binding specificity of rat IRF compared with that of the related IRE-binding protein, IRFB.
