Abstract
Tight control of p63 protein levels must be achieved under differentiation or apoptotic conditions. Here, we describe a new regulatory pathway for the DeltaNp63alpha protein. We found that MDM2 binds DeltaNp63alpha in the nucleus promoting its translocation to the cytoplasm. The MDM2 nuclear localization signal is required for DeltaNp63alpha nuclear export and subsequent degradation, whereas the MDM2 ring-finger domain is dispensable. Once exported to the cytoplasm by MDM2, p63 is targeted for degradation by the Fbw7 E3-ubiquitin ligase. Efficient degradation of DeltaNp63alpha by Fbw7 (also known as FBXW7) requires GSK3 kinase activity. By deletion and point mutations analysis we have identified a phosphodegron located in the alpha and beta tail of p63 that is required for degradation. Furthermore, we show that MDM2 or Fbw7 depletion inhibits degradation of endogenous DeltaNp63alpha in cells exposed to UV irradiation, adriamycin and upon keratinocyte differentiation. Our findings suggest that following DNA damage and cellular differentiation MDM2 and Fbw7 can cooperate to regulate the levels of the pro-proliferative DeltaNp63alpha protein.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Active Transport, Cell Nucleus / drug effects
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Active Transport, Cell Nucleus / genetics
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Active Transport, Cell Nucleus / radiation effects
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Animals
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism*
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Cell Differentiation / drug effects
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Cell Differentiation / radiation effects
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Cell Line, Tumor
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Cell Nucleus / drug effects
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Cell Nucleus / metabolism*
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Cell Nucleus / radiation effects
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Cell Proliferation / drug effects
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Cell Proliferation / radiation effects
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DNA Damage / genetics
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Doxorubicin / pharmacology
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F-Box Proteins / genetics
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F-Box Proteins / metabolism*
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F-Box-WD Repeat-Containing Protein 7
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Humans
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Mice
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Mutation / genetics
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Protein Binding / genetics
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Protein Structure, Tertiary / genetics
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Proto-Oncogene Proteins c-mdm2 / genetics
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Proto-Oncogene Proteins c-mdm2 / metabolism*
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RNA, Small Interfering / genetics
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Trans-Activators / genetics
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Trans-Activators / metabolism*
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Transcription Factors
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Transcriptional Activation / genetics
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Tumor Suppressor Protein p53 / metabolism
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Tumor Suppressor Proteins / genetics
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Tumor Suppressor Proteins / metabolism*
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Ubiquitin-Protein Ligases / genetics
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Ubiquitin-Protein Ligases / metabolism*
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Ultraviolet Rays / adverse effects
Substances
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Cell Cycle Proteins
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F-Box Proteins
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F-Box-WD Repeat-Containing Protein 7
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FBXW7 protein, human
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RNA, Small Interfering
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TP63 protein, human
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Trans-Activators
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Transcription Factors
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Tumor Suppressor Protein p53
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Tumor Suppressor Proteins
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Doxorubicin
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Proto-Oncogene Proteins c-mdm2
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Ubiquitin-Protein Ligases