Observation of unphosphorylated STAT3 core protein binding to target dsDNA by PEMSA and X-ray crystallography

FEBS Lett. 2013 Apr 2;587(7):833-9. doi: 10.1016/j.febslet.2013.01.065. Epub 2013 Feb 19.


The STAT3 transcription factor plays a central role in a wide range of cancer types where it is over-expressed. Previously, phosphorylation of this protein was thought to be a prerequisite for direct binding to DNA. However, we have now shown complete binding of a purified unphosphorylated STAT3 (uSTAT3) core directly to M67 DNA, the high affinity STAT3 target DNA sequence, by a protein electrophoretic mobility shift assay (PEMSA). Binding to M67 DNA was inhibited by addition of increasing concentrations of a phosphotyrosyl peptide. X-ray crystallography demonstrates one mode of binding that is similar to that known for the STAT3 core phosphorylated at Y705.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites
  • Binding, Competitive
  • Circular Dichroism
  • Crystallography, X-Ray
  • DNA / chemistry*
  • DNA / genetics
  • DNA / metabolism*
  • Electrophoretic Mobility Shift Assay / methods*
  • Humans
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Models, Molecular
  • Nucleic Acid Conformation
  • Phosphopeptides / chemistry
  • Phosphopeptides / metabolism
  • Phosphorylation
  • Protein Binding
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • STAT3 Transcription Factor / chemistry*
  • STAT3 Transcription Factor / genetics
  • STAT3 Transcription Factor / metabolism*
  • Tyrosine / chemistry
  • Tyrosine / genetics
  • Tyrosine / metabolism


  • Luminescent Proteins
  • Phosphopeptides
  • STAT3 Transcription Factor
  • Tyrosine
  • DNA