EYA1's Conformation Specificity in Dephosphorylating Phosphothreonine in Myc and Its Activity on Myc Stabilization in Breast Cancer

Mol Cell Biol. 2016 Dec 19;37(1):e00499-16. doi: 10.1128/MCB.00499-16. Print 2017 Jan 1.


EYA1 is known to be overexpressed in human breast cancer, in which the Myc protein is also accumulated in association with decreased phospho-T58 (pT58) levels. We have recently reported that EYA1 functions as a unique protein phosphatase to dephosphorylate Myc at pT58 to regulate Myc levels. However, it remains unclear whether EYA1-mediated Myc dephosphorylation on T58 is a critical function in regulating Myc protein stability in breast cancer. Furthermore, EYA1's substrate specificity has remained elusive. In this study, we have investigated these questions, and here, we report that depletion of EYA1 using short hairpin RNA (shRNA) in breast cancer cells destabilizes the Myc protein and increases pT58 levels, leading to an increase in the doubling time and impairment of cell cycle progression. In correlation with EYA1-mediated stabilization of cMyc and reduced levels of pT58, EYA1 greatly reduced cMyc-FBW7 binding and cMyc ubiquitination, thus providing novel insight into how EYA1 acts to regulate the FBW7-mediated Myc degradation machinery. We found that the conserved C-terminal haloacid dehalogenase domain of EYA1, which has been reported to have only tyrosine phosphatase activity, has dual phosphatase activities, and both the N- and C-terminal domains interact with substrates to increase the catalytic activity of EYA1. Enzymatic assay and nuclear magnetic resonance (NMR) analysis demonstrated that EYA1 has a striking conformation preference for phospho-T58 of Myc. Together, our results not only provide novel structural evidence about the conformation specificity of EYA1 in dephosphorylating phosphothreonine in Myc but also reveal an important mechanism contributing to Myc deregulation in human breast cancer.

Keywords: EYA1; FBW7; Myc; breast cancer; cell proliferation; degradation; deregulation; threonine phosphatase.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Breast Neoplasms / metabolism*
  • Cell Cycle
  • Cell Cycle Proteins / metabolism*
  • Cell Line, Tumor
  • F-Box Proteins / metabolism*
  • F-Box-WD Repeat-Containing Protein 7
  • Female
  • Gene Expression Regulation, Neoplastic
  • Humans
  • Intracellular Signaling Peptides and Proteins / chemistry*
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Models, Molecular
  • Nuclear Proteins / chemistry*
  • Nuclear Proteins / metabolism*
  • Phosphorylation
  • Protein Binding
  • Protein Conformation
  • Protein Stability
  • Protein Tyrosine Phosphatases / chemistry*
  • Protein Tyrosine Phosphatases / metabolism*
  • Proto-Oncogene Proteins c-myc / chemistry
  • Proto-Oncogene Proteins c-myc / metabolism*
  • Threonine / metabolism
  • Ubiquitin-Protein Ligases / metabolism*


  • Cell Cycle Proteins
  • F-Box Proteins
  • F-Box-WD Repeat-Containing Protein 7
  • FBXW7 protein, human
  • Intracellular Signaling Peptides and Proteins
  • MYC protein, human
  • Nuclear Proteins
  • Proto-Oncogene Proteins c-myc
  • Threonine
  • Ubiquitin-Protein Ligases
  • EYA1 protein, human
  • Protein Tyrosine Phosphatases