Cysteine oxidation regulates the RNA-binding activity of iron regulatory protein 2

Mol Cell Biol. 2009 Apr;29(8):2219-29. doi: 10.1128/MCB.00004-09. Epub 2009 Feb 17.

Abstract

Iron regulatory protein 2 (IRP2) is an RNA-binding protein that regulates the posttranscriptional expression of proteins required for iron homeostasis such as ferritin and transferrin receptor 1. IRP2 RNA-binding activity is primarily regulated by iron-mediated proteasomal degradation, but studies have suggested that IRP2 RNA binding is also regulated by thiol oxidation. We generated a model of IRP2 bound to RNA and found that two cysteines (C512 and C516) are predicted to lie in the RNA-binding cleft. Site-directed mutagenesis and thiol modification show that, while IRP2 C512 and C516 do not directly interact with RNA, both cysteines are located within the RNA-binding cleft and must be unmodified/reduced for IRP2-RNA interactions. Oxidative stress induced by cellular glucose deprivation reduces the RNA-binding activity of IRP2 but not IRP2-C512S or IRP2-C516S, consistent with the formation of a disulfide bond between IRP2 C512 and C516 during oxidative stress. Decreased IRP2 RNA binding is correlated with reduced transferrin receptor 1 mRNA abundance. These studies provide insight into the structural basis for IRP2-RNA interactions and reveal an iron-independent mechanism for regulating iron homeostasis through the redox regulation of IRP2 cysteines.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Antigens, CD / genetics*
  • Binding Sites
  • Cysteine / metabolism*
  • Homeostasis
  • Humans
  • Iron Regulatory Protein 2 / metabolism*
  • Mice
  • Oxidation-Reduction
  • Oxidative Stress
  • RNA, Messenger / analysis
  • RNA-Binding Proteins / metabolism*
  • Receptors, Transferrin / genetics*

Substances

  • Antigens, CD
  • CD71 antigen
  • RNA, Messenger
  • RNA-Binding Proteins
  • Receptors, Transferrin
  • Iron Regulatory Protein 2
  • Cysteine