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

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

Author information

1
Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
2
Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
3
Department of Natural Sciences, Hostos Community College of CUNY, Bronx, New York, USA.
4
First Hospital of Jilin University, Chang Chun, China.
5
Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA pinxian.xu@mssm.edu.
6
Department of Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, New York, USA.

Abstract

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

PMID:
27795300
PMCID:
PMC5192086
DOI:
10.1128/MCB.00499-16
[Indexed for MEDLINE]
Free PMC Article

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