Heterogeneous nuclear ribonucleoprotein K inhibits heat shock-induced transcriptional activity of heat shock factor 1

J Biol Chem. 2017 Aug 4;292(31):12801-12812. doi: 10.1074/jbc.M117.774992. Epub 2017 Jun 7.

Abstract

When cells are exposed to heat shock and various other stresses, heat shock factor 1 (HSF1) is activated, and the heat shock response (HSR) is elicited. To better understand the molecular regulation of the HSR, we used 2D-PAGE-based proteome analysis to screen for heat shock-induced post-translationally modified cellular proteins. Our analysis revealed that two protein spots typically present on 2D-PAGE gels and containing heterogeneous nuclear ribonucleoprotein K (hnRNP K) with trioxidized Cys132 disappeared after the heat shock treatment and reappeared during recovery, but the total amount of hnRNP K protein remained unchanged. We next tested whether hnRNP K plays a role in HSR by regulating HSF1 and found that hnRNP K inhibits HSF1 activity, resulting in reduced expression of hsp70 and hsp27 mRNAs. hnRNP K also reduced binding affinity of HSF1 to the heat shock element by directly interacting with HSF1 but did not affect HSF1 phosphorylation-dependent activation or nuclear localization. hnRNP K lost its ability to induce these effects when its Cys132 was substituted with Ser, Asp, or Glu. These findings suggest that hnRNP K inhibits transcriptional activity of HSF1 by inhibiting its binding to heat shock element and that the oxidation status of Cys132 in hnRNP K is critical for this inhibition.

Keywords: Heat shock factor protein 1 (HSF1); heat shock protein (HSP); hnRNP K; mass spectrometry (MS); post-translational modification (PTM); proteomics; redox regulation.

MeSH terms

  • Amino Acid Substitution
  • Animals
  • Cell Line, Tumor
  • Cystine / metabolism
  • DNA-Binding Proteins / antagonists & inhibitors*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Gene Expression Profiling
  • Gene Expression Regulation*
  • HEK293 Cells
  • HSP27 Heat-Shock Proteins / antagonists & inhibitors*
  • HSP27 Heat-Shock Proteins / genetics
  • HSP27 Heat-Shock Proteins / metabolism
  • HSP70 Heat-Shock Proteins / antagonists & inhibitors*
  • HSP70 Heat-Shock Proteins / genetics
  • HSP70 Heat-Shock Proteins / metabolism
  • Heat Shock Transcription Factors
  • Heat-Shock Proteins
  • Heterogeneous-Nuclear Ribonucleoprotein K / antagonists & inhibitors
  • Heterogeneous-Nuclear Ribonucleoprotein K / genetics
  • Heterogeneous-Nuclear Ribonucleoprotein K / metabolism*
  • Hot Temperature / adverse effects
  • Humans
  • Mice
  • Molecular Chaperones
  • Mutation
  • Oxidation-Reduction
  • Protein Processing, Post-Translational*
  • RNA Interference
  • RNA, Messenger / metabolism
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Response Elements*
  • Ribonucleoproteins / antagonists & inhibitors
  • Ribonucleoproteins / genetics
  • Ribonucleoproteins / metabolism
  • Transcription Factors / antagonists & inhibitors*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism

Substances

  • DNA-Binding Proteins
  • HSF1 protein, human
  • HSP27 Heat-Shock Proteins
  • HSP70 Heat-Shock Proteins
  • HSPB1 protein, human
  • Heat Shock Transcription Factors
  • Heat-Shock Proteins
  • Heterogeneous-Nuclear Ribonucleoprotein K
  • Molecular Chaperones
  • RNA, Messenger
  • Recombinant Fusion Proteins
  • Ribonucleoproteins
  • Transcription Factors
  • HNRNPK protein, human
  • Cystine