REQUIREMENTS FOR IRON-REGULATED DEGRADATION OF THE RNA-BINDING PROTEIN, IRON REGULATORY PROTEIN-2
REQUIREMENTS FOR IRON-REGULATED DEGRADATION OF THE RNA-BINDING PROTEIN, IRON REGULATORY PROTEIN-2
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DOI：
10.1002/j.1460-2075.1995.tb00219.x
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发表时间：
1995-11-01
期刊：
影响因子：
11.4
通讯作者：
ROUAULT, TA
中科院分区：
文献类型：
--
作者：
IWAI, K;KLAUSNER, RD;ROUAULT, TA
铁调节蛋白（IRP）调节参与铁代谢的基因的表达，其转录物含有称为铁响应元件（IRE）的RNA茎环元件。当铁浓度低时，IRP在转录物的5'非翻译区（UTR）结合IRE，在该处IRP抑制翻译，或在转录物的3' UTR处IRE抑制降解，同源蛋白IRP1和IRP2的RNA结合活性都是在转录后调节的。当细胞充满铁时，IRP2的结合活性受到蛋白质降解的调节。在这里，我们证明了对应于IRP2中独特外显子的73个氨基酸序列包含在充满铁的细胞中快速降解所需的序列。该序列的缺失消除了IRP2的快速周转，而将该序列转移到同源蛋白IRP 1中的相应位置赋予IRP 1铁依赖性降解的能力，定点诱变已经证明，IRP2外显子内的特异性半胱氨酸是铁依赖性降解所必需的。在铁充足的细胞中，IRP2的降解似乎是由蛋白酶体介导的，当降解被阻止时，IRP2的RNA结合活性不受铁浓度的调节，因此，IRP2的RNA结合活性的调节需要降解。
Iron regulatory proteins (IRPs) regulate the expression of genes involved in iron metabolism whose transcripts contain RNA stem-loop moths known as iron-responsive elements (IREs), When iron concentrations are low, IRPs bind to IREs in the 5' untranslated region (UTR) of transcripts where they repress translation, or the 3' UTR of transcripts where they inhibit degradation, The RNA binding activities of the homologous proteins IRP1 and IRP2 are both regulated posttranslationally. The binding activity of IRP2 is regulated by the degradation of the protein when cells are iron-replete, Here, we demonstrate that a 73 amino acid sequence that corresponds to a unique exon in IRP2 contains a sequence required for rapid degradation in iron-replete cells, The deletion of this sequence eliminates the rapid turnover of IRP2, whereas the transfer of this sequence to the corresponding position in the homologous protein IRP1 confers the capacity for iron-dependent degradation upon IRP1, Site-directed mutagenesis has demonstrated that specific cysteines within the IRP2 exon are required for iron-dependent degradation, The degradation of IRP2 appears to be mediated by the proteasome in iron-replete cells, When degradation is prevented, the RNA binding activity of IRP2 is not regulated by iron concentration, Thus, degradation is required for the regulation of the RNA binding activity of IRP2.