Expression of the rat liver haptoglobin gene is mediated by isoforms of C/EBPalpha, -beta and -delta proteins

Gen Physiol Biophys. 2003 Jun;22(2):181-90.

Abstract

CCAAT/enhancer binding proteins (C/EBP) alpha, -beta and -delta play an important role in mediating I interleukin-6 (IL-6) dependent expression of acute-phase protein (APP) genes in liver during acute-phase (AP) response. Based on the presence of type IL-6 responsive element (IL-6 RE) in the rat haptoglobin (Hp) gene promoter we assumed that some C/EBPalpha, -beta and/or -delta isoforms could mediate the expression of this gene during turpentine-induced AP response. By Western immunoblot and Northern blot assays, we found that turpentine treatment of rats led to a coordinate induction of C/EBPbeta and -delta as well as repression of C/EBPalpha isoforms pool levels in rat liver nuclear extracts (NEs) which was preceded by an adequate alteration of their mRNAs expression in liver. Consequently, results of DNA affinity chromatography revealed that affinity of certain C/EBPalpha isoforms to bind the type I IL-6 RE within the rat Hp gene promoter decreased whereas affinities of certain C/EBPbeta isoforms and C/EBPdelta were increased and induced, respectively. Our data suggest that turpentine-induced alterations of C/EBPalpha, -beta and -delta pool levels and DNA-binding activities can be regarded as an integral part of activation of the Hp gene expression in the course of AP response.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acute-Phase Reaction / chemically induced
  • Acute-Phase Reaction / genetics*
  • Acute-Phase Reaction / immunology
  • Acute-Phase Reaction / metabolism*
  • Animals
  • CCAAT-Enhancer-Binding Proteins / genetics*
  • CCAAT-Enhancer-Binding Proteins / metabolism*
  • Gene Expression Regulation*
  • Haptoglobins / genetics*
  • Haptoglobins / metabolism*
  • Liver / drug effects
  • Liver / metabolism*
  • Male
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Rats
  • Rats, Wistar

Substances

  • CCAAT-Enhancer-Binding Proteins
  • Haptoglobins
  • Protein Isoforms