Identification of human genes of iron homeostasis

铁依赖性酶接受其金属辅因子的机制在很大程度上是未知的。多聚腺苷酸结合蛋白1（PCBP 1）是铁蛋白的铁分子伴侣; PCBP 1和它的伴侣PCBP 2都是将铁传递到调节HIF 1的脯氨酰羟化酶所必需的。在这里，我们表明PCBP 2也是铁蛋白的铁伴侣。PCBP 2和人铁蛋白在酵母中的共表达激活了缺铁反应，并增加了铁沉积到铁蛋白中。在Huh 7细胞中PCBP 2的消耗减少了铁掺入铁蛋白。PCBP 1和PCBP 2均与HEK 293细胞中的铁蛋白共免疫沉淀，并且两种PCBP的表达是细胞中铁蛋白复合物形成所需的。PCBP 1和2在体外表现出与铁蛋白的高亲和力结合。哺乳动物基因组编码4种PCBP，包括最低表达的PCBP 3和4。PCBP 3和4在酵母中的表达激活了缺铁反应，但只有PCBP 3表现出与铁蛋白的强相互作用。PCBP 1和铁蛋白在铁敏感的ccc 1酵母菌株中的表达增强了铁的毒性作用，而PCBP 4的表达保护细胞免受铁毒性。因此，PCBP 1和2形成一个复杂的铁传递到铁蛋白和所有的PCBPs可以共享铁伴侣活性。

The mechanisms through which iron-dependent enzymes receive their metal cofactors are largely unknown. Poly r(C) Binding Protein 1 (PCBP1) is an iron chaperone for ferritin; both PCBP1 and its paralog PCBP2 are required for iron delivery to the prolyl hydroxylase that regulates HIF1. Here we show that PCBP2 is also an iron chaperone for ferritin. Co-expression of PCBP2 and human ferritins in yeast activated the iron deficiency response and increased iron deposition into ferritin. Depletion of PCBP2 in Huh7 cells diminished iron incorporation into ferritin. Both PCBP1 and PCBP2 were co-immunoprecipitated with ferritin in HEK293 cells and expression of both PCBPs was required for ferritin complex formation in cells. PCBP1 and 2 exhibited high-affinity binding to ferritin in vitro. Mammalian genomes encode 4 PCBPs, including the minimally expressed PCBPs 3 and 4. Expression of PCBP3 and 4 in yeast activated the iron deficiency response, but only PCBP3 exhibited strong interactions with ferritin. Expression of PCBP1 and ferritin in an iron sensitive, ccc1 yeast strain intensified the toxic effects of iron, while expression of PCBP4 protected the cells from iron toxicity. Thus, PCBP1 and 2 form a complex for iron delivery to ferritin and all PCBPs may share iron chaperone activity.