Oncogenic N-Ras Stimulates SRF-Mediated Transactivation via H3 Acetylation at Lysine 9

Biomed Res Int. 2018 Jan 3:2018:5473725. doi: 10.1155/2018/5473725. eCollection 2018.

Abstract

Signal transduction pathways regulate the gene expression by altering chromatin dynamics in response to mitogens. Ras proteins are key regulators linking extracellular stimuli to a diverse range of biological responses associated with gene regulation. In mammals, the three ras genes encode four Ras protein isoforms: H-Ras, K-Ras4A, K-Ras4B, and N-Ras. Although emerging evidence suggests that Ras isoforms differentially regulate gene expressions and are functionally nonredundant, the mechanisms underlying Ras specificity and Ras signaling effects on gene expression remain unclear. Here, we show that oncogenic N-Ras acts as the most potent regulator of SRF-, NF-κB-, and AP-1-dependent transcription. N-Ras-RGL2 axis is a distinct signaling pathway for SRF target gene expression such as Egr1 and JunB, as RGL2 Ras binding domain (RBD) significantly impaired oncogenic N-Ras-induced SRE activation. By monitoring the effect of Ras isoforms upon the change of global histone modifications in oncogenic Ras-overexpressed cells, we discovered that oncogenic N-Ras elevates H3K9ac/H3K23ac levels globally in the chromatin context. Importantly, chromatin immunoprecipitation (ChIP) assays revealed that H3K9ac is significantly enriched at the promoter and coding regions of Egr1 and JunB. Collectively, our findings define an undocumented role of N-Ras in modulating of H3 acetylation and in gene regulation.

MeSH terms

  • Acetylation
  • Animals
  • Cell Line
  • Chlorocebus aethiops
  • Chromatin / genetics*
  • Chromatin Immunoprecipitation
  • Early Growth Response Protein 1
  • GTP Phosphohydrolases / genetics
  • Gene Expression Regulation / genetics
  • HEK293 Cells
  • Histones / genetics
  • Humans
  • Lysine / genetics
  • Lysine / metabolism
  • Membrane Proteins / genetics
  • NF-kappa B / genetics
  • Promoter Regions, Genetic
  • Protein Isoforms / genetics
  • Protein Processing, Post-Translational / genetics*
  • Proto-Oncogene Proteins p21(ras) / genetics
  • Signal Transduction / genetics*
  • Transcription Factors / genetics
  • Transcriptional Activation / genetics*

Substances

  • Chromatin
  • EGR1 protein, human
  • Early Growth Response Protein 1
  • Histones
  • JunB protein, human
  • KRAS protein, human
  • Membrane Proteins
  • NF-kappa B
  • Protein Isoforms
  • Transcription Factors
  • GTP Phosphohydrolases
  • NRAS protein, human
  • HRAS protein, human
  • Proto-Oncogene Proteins p21(ras)
  • Lysine