Phosphorylation of H2AX at Ser139 and a new phosphorylation site Ser16 by RSK2 decreases H2AX ubiquitination and inhibits cell transformation

Cancer Res. 2011 Jan 15;71(2):393-403. doi: 10.1158/0008-5472.CAN-10-2012. Epub 2011 Jan 11.


Histone H2AX is a histone H2A variant that is ubiquitously expressed throughout the genome. It plays a key role in the cellular response to DNA damage and has been designated as the histone guardian of the genome. Histone H2AX deficiency decreases genomic stability and increases tumor susceptibility of normal cells and tissues. However, the role of histone H2AX phosphorylation in malignant transformation and cancer development is not totally clear. Herein, we found that ribosomal S6 kinase 2 (RSK2) directly phosphorylates histone H2AX at Ser139 and also at a newly discovered site, Ser16. Epidermal growth factor (EGF)-induced phosphorylation of histone H2AX at both sites was decreased in RSK2 knockout cells. Phosphorylated RSK2 and histone H2AX colocalized in the nucleus following EGF treatment, and the phosphorylation of histone H2AX by RSK2 enhanced the stability of histone H2AX and prevented cell transformation induced by EGF. RSK2 and DNA-PK, but not ATM or ATR, are required for EGF-induced phosphorylation of H2AX at Ser139; however, only RSK2 is required for phosphorylation of H2AX at Ser16. Phosphorylation of histone H3 was suppressed in cells expressing wild-type H2AX compared with H2AX knockout (H2AX-/-) cells. EGF-associated AP-1 transactivation activity was dramatically lower in H2AX-/- cells overexpressing wild-type H2AX than H2AX-/- cells expressing mutant H2AX-AA. Thus, the RSK2/H2AX signaling pathway negatively regulates the RSK2/histone H3 pathway and therefore maintains normal cell proliferation.

Publication types

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

MeSH terms

  • Ataxia Telangiectasia Mutated Proteins
  • Cell Adhesion / physiology
  • Cell Cycle Proteins / metabolism
  • Cell Growth Processes / physiology
  • Cell Transformation, Neoplastic / metabolism*
  • Cell Transformation, Neoplastic / pathology
  • DNA-Activated Protein Kinase / metabolism
  • DNA-Binding Proteins / metabolism
  • Epidermal Growth Factor / pharmacology
  • HeLa Cells
  • Histones / biosynthesis
  • Histones / metabolism*
  • Humans
  • Phosphorylation
  • Protein Serine-Threonine Kinases / metabolism
  • Ribosomal Protein S6 Kinases, 90-kDa / metabolism*
  • Serine / metabolism
  • Tumor Suppressor Proteins / metabolism
  • Ubiquitination


  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • H2AX protein, human
  • Histones
  • Tumor Suppressor Proteins
  • Serine
  • Epidermal Growth Factor
  • ATM protein, human
  • ATR protein, human
  • Ataxia Telangiectasia Mutated Proteins
  • DNA-Activated Protein Kinase
  • Protein Serine-Threonine Kinases
  • Ribosomal Protein S6 Kinases, 90-kDa
  • ribosomal protein S6 kinase, 90kDa, polypeptide 3