An iron responsive element-like stem-loop regulates alpha-hemoglobin-stabilizing protein mRNA

J Biol Chem. 2008 Oct 3;283(40):26956-64. doi: 10.1074/jbc.M802421200. Epub 2008 Aug 2.

Abstract

Hemoglobin production during erythropoiesis is mechanistically coupled to the acquisition and metabolism of iron. We discovered that iron regulates the expression of alpha-hemoglobin-stabilizing protein (AHSP), a molecular chaperone that binds and stabilizes free alpha-globin during hemoglobin synthesis. In primates, the 3'-untranslated region (UTR) of AHSP mRNA contains a nucleotide sequence resembling iron responsive elements (IREs), stem-loop structures that regulate gene expression post-transcriptionally by binding iron regulatory proteins (IRPs). The AHSP IRE-like stem-loop deviates from classical consensus sequences and binds IRPs poorly in electrophoretic mobility shift assays. However, in cytoplasmic extracts, AHSP mRNA co-immunoprecipitates with IRPs in a fashion that is dependent on the stem-loop structure and inhibited by iron. Moreover, this interaction enhances AHSP mRNA stability in erythroid and heterologous cells. Our findings demonstrate that IRPs can regulate mRNA expression through non-canonical IREs and extend the repertoire of known iron-regulated genes. In addition, we illustrate a new mechanism through which hemoglobin may be modulated according to iron status.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3' Untranslated Regions / genetics
  • 3' Untranslated Regions / metabolism*
  • Blood Proteins / genetics
  • Blood Proteins / metabolism*
  • Erythropoiesis / physiology*
  • HeLa Cells
  • Hemoglobins / biosynthesis
  • Hemoglobins / genetics
  • Humans
  • Iron / metabolism*
  • K562 Cells
  • Molecular Chaperones / genetics
  • Molecular Chaperones / metabolism*
  • Nucleic Acid Conformation
  • RNA Stability / physiology*

Substances

  • 3' Untranslated Regions
  • AHSP protein, human
  • Blood Proteins
  • Hemoglobins
  • Molecular Chaperones
  • Iron