Iron Availability Modulates Aberrant Splicing of Ferrochelatase Through the Iron- And 2-oxoglutarate Dependent Dioxygenase Jmjd6 and U2AF(65.)

Blood Cells Mol Dis. 2013 Oct;51(3):151-61. doi: 10.1016/j.bcmd.2013.05.008. Epub 2013 Jun 18.

Abstract

Erythropoietic protoporphyria (EPP) results from partial deficiency of ferrochelatase (FECH). Genetically, EPP patients differ from asymptomatic mutation carriers at the unmutated FECH allele, the expression of which is modulated by single nucleotide polymorphism IVS3-48C/T. The IVS3-48C genotype, which is present among patients, leads to correct splicing of 60% of the pre-mRNA and to alternative splicing of 40%, the latter mRNA-product being destroyed by nonsense-mediated decay. An IVS3-48T genotype generates 80% correct and 20% aberrant products. Our study demonstrated that under iron deficient conditions, the aberrant splice product was increased to 56% and 50% of total FECH mRNA in erythroleukemic K562 and lymphoblastoid cell lines, respectively, both being homozygous for IVS3-48T. Concomitantly, FECH protein was decreased. Iron deficiency had less effect on the FECH splice ratio in an IVS3-48C/C lymphoblastoid cell line. Effects similar to iron deficiency were generated by siRNA knockdown of either splicing factor U2AF(65) or Fe(II)- and 2-oxoglutarate-dependent dioxygenase Jumonji domain-containing protein 6 (Jmjd6), which interacts with U2AF(65) by lysyl-hydroxylation. Based on these results, we propose that the availability of iron, a co-factor of Jmjd6, modulates U2AF(65)-lysyl-hydroxylation. This in turn, influences the relative amounts of correct and aberrant FECH mRNA splice products and thus, regulates the FECH enzyme activity.

Keywords: Aberrant splicing; Ferrochelatase; Iron; Jmjd6; U2AF(65).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alternative Splicing*
  • Base Sequence
  • Case-Control Studies
  • Cell Line
  • Cobalt / pharmacology
  • Deferoxamine / metabolism
  • Deferoxamine / pharmacology
  • Ferrochelatase / genetics*
  • Ferrochelatase / metabolism
  • Gene Expression Regulation / drug effects
  • Gene Order
  • Gene Silencing
  • Genotype
  • Humans
  • Introns
  • Iron / metabolism*
  • Jumonji Domain-Containing Histone Demethylases / antagonists & inhibitors
  • Jumonji Domain-Containing Histone Demethylases / metabolism*
  • K562 Cells
  • Ketoglutaric Acids / metabolism*
  • Molecular Sequence Data
  • Mutation
  • Nuclear Proteins / metabolism*
  • Polymorphism, Single Nucleotide
  • Protoporphyria, Erythropoietic / genetics
  • Protoporphyria, Erythropoietic / metabolism
  • RNA Interference
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Ribonucleoproteins / metabolism*
  • Sequence Alignment
  • Splicing Factor U2AF

Substances

  • Ketoglutaric Acids
  • Nuclear Proteins
  • RNA, Messenger
  • Ribonucleoproteins
  • Splicing Factor U2AF
  • U2AF2 protein, human
  • Cobalt
  • Iron
  • JMJD6 protein, human
  • Jumonji Domain-Containing Histone Demethylases
  • Ferrochelatase
  • cobaltous chloride
  • Deferoxamine