Abstract
We report that in breast cancer cells, tyrosine phosphorylation of the estradiol receptor alpha (ERalpha) by Src regulates cytoplasmic localization of the receptor and DNA synthesis. Inhibition of Src or use of a peptide mimicking the ERalpha p-Tyr537 sequence abolishes ERalpha tyrosine phosphorylation and traps the receptor in nuclei of estradiol-treated MCF-7 cells. An ERalpha mutant carrying a mutation of Tyr537 to phenylalanine (ER537F) persistently localizes in nuclei of various cell types. In contrast with ERalpha wt, ER537F does not associate with Ran and its interaction with Crm1 is insensitive to estradiol. Thus, independently of estradiol, ER537F is retained in nuclei, where it entangles FKHR-driving cell cycle arrest. Chromatin immunoprecipitation analysis reveals that overexpression of ER537F in breast cancer cells enhances FKHR interaction with cyclin D1 promoter. This mutant also counteracts cell transformation by the activated forms of Src or PI3-K. In conclusion, in addition to regulating receptor localization, ERalpha phosphorylation by Src is required for hormone responsiveness of DNA synthesis in breast cancer cells.
MeSH terms
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Active Transport, Cell Nucleus
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Animals
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Breast Neoplasms / enzymology
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Breast Neoplasms / genetics
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Breast Neoplasms / metabolism*
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Breast Neoplasms / pathology
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COS Cells
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Cell Cycle Checkpoints / genetics
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Cell Cycle Checkpoints / physiology*
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Cell Growth Processes / genetics
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Cell Growth Processes / physiology
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Cell Line
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Cell Line, Tumor
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Cell Nucleus / genetics
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Cell Nucleus / metabolism
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Chlorocebus aethiops
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Cyclin D1 / genetics
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Cyclin D1 / metabolism
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Cytoplasm / genetics
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Cytoplasm / metabolism
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Estradiol / metabolism*
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Estrogen Receptor alpha / genetics
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Estrogen Receptor alpha / metabolism*
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Exportin 1 Protein
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Female
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Forkhead Transcription Factors / genetics
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Forkhead Transcription Factors / metabolism
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Humans
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Karyopherins / genetics
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Karyopherins / metabolism
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MCF-7 Cells
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Mice
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Mutation
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NIH 3T3 Cells
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Phenylalanine / genetics
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Phenylalanine / metabolism
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Phosphatidylinositol 3-Kinases / genetics
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Phosphatidylinositol 3-Kinases / metabolism
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Phosphorylation
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Promoter Regions, Genetic
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Receptors, Cytoplasmic and Nuclear / genetics
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Receptors, Cytoplasmic and Nuclear / metabolism
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S Phase / genetics
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Transcription, Genetic
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Tyrosine / genetics
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Tyrosine / metabolism*
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ran GTP-Binding Protein / genetics
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ran GTP-Binding Protein / metabolism
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src-Family Kinases / genetics
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src-Family Kinases / metabolism*
Substances
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Estrogen Receptor alpha
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Forkhead Transcription Factors
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Karyopherins
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Receptors, Cytoplasmic and Nuclear
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Cyclin D1
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Tyrosine
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Phenylalanine
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Estradiol
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src-Family Kinases
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ran GTP-Binding Protein