Iron chaperones PCBP1 and PCBP2 mediate the metallation of the dinuclear iron enzyme deoxyhypusine hydroxylase.
Although cells express hundreds of metalloenzymes, the mechanisms by which apoenzymes receive their metal cofactors are largely unknown. Poly(rC)-binding proteins PCBP1 and PCBP2 are multifunctional adaptor proteins that bind iron and deliver it to ferritin for storage or to prolyl and asparagyl hydroxylases to metallate the mononuclear iron center. Here, we show that PCBP1 and PCBP2 also deliver iron to deoxyhypusine hydroxylase (DOHH), the dinuclear iron enzyme required for hypusine modification of the translation factor eukaryotic initiation factor 5A. Cells depleted of PCBP1 or PCBP2 exhibited loss of DOHH activity and loss of the holo form of the enzyme in cells, particularly when cells were made mildly iron-deficient. Lysates containing PCBP1 and PCBP2 converted apo-DOHH to holo-DOHH in vitro with greater efficiency than lysates lacking PCBP1 or PCBP2. PCBP1 bound to DOHH in iron-treated cells but not in control or iron-deficient cells. Depletion of PCBP1 or PCBP2 had no effect on the cytosolic Fe-S cluster enzyme xanthine oxidase but led to loss of cytosolic aconitase activity. Loss of aconitase activity was not accompanied by gain of RNA-binding activity, a pattern suggesting the incomplete disassembly of the [4Fe-4S] cluster. PCBP depletions had minimal effects on total cellular iron, mitochondrial iron levels, and heme synthesis. Thus, PCBP1 and PCBP2 may serve as iron chaperones to multiple classes of cytosolic nonheme iron enzymes and may have a particular role in restoring metal cofactors that are spontaneously lost in iron deficient cells.
Liver Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892;
Avery G
AG
Frey
Liver Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892;
Anjali
A
Nandal
Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892;
Jong Hwan
JH
Park
Liver Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892;
Pamela M
PM
Smith
Liver Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892;
Toshiki
T
Yabe
Liver Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892;
Moon-Suhn
MS
Ryu
Molecular Medicine Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892; and.
Manik C
MC
Ghosh
Department of Biochemistry and Redox Biology Center, University of Nebraska, Lincoln, NE 68516.
Jaekwon
J
Lee
Molecular Medicine Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892; and.
Tracey A
TA
Rouault
Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892;
Myung Hee
MH
Park
Liver Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892; carolinep@intra.niddk.nih.gov.
Caroline C
CC
Philpott
D006528:Carcinoma, Hepatocellular; D003600:Cytosol / Q000378:metabolism; D004268:DNA-Binding Proteins; D005293:Ferritins / Q000378:metabolism*; D057809:HEK293 Cells; D006418:Heme / Q000096:biosynthesis; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007501:Iron / Q000378:metabolism*; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D008113:Liver Neoplasms; D008928:Mitochondria / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D018832:Molecular Chaperones / Q000378:metabolism; D010448:Peptide Initiation Factors / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000097574:Eukaryotic Translation Initiation Factor 5A
D004268:DNA-Binding Proteins; D005293:Ferritins; D006418:Heme; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D007501:Iron; D007506:Iron-Sulfur Proteins; D006899:Mixed Function Oxygenases; D018832:Molecular Chaperones; D010448:Peptide Initiation Factors; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D000097574:Eukaryotic Translation Initiation Factor 5A; C094604:PCBP1 protein, human; C501903:PCBP2 protein, human; C047991:deoxyhypusine hydroxylase
diiron enzyme; iron regulatory protein