Abstract
Tumorigenesis results from dysregulation of oncogenes and tumor suppressors that influence cellular proliferation, differentiation, apoptosis, and/or senescence. Many gene products involved in these processes are substrates of the E3 ubiquitin ligase Mule/Huwe1/Arf-BP1 (Mule), but whether Mule acts as an oncogene or tumor suppressor in vivo remains controversial. We generated K14Cre;Mule(flox/flox(y)) (Mule kKO) mice and subjected them to DMBA/PMA-induced skin carcinogenesis, which depends on oncogenic Ras signaling. Mule deficiency resulted in increased penetrance, number, and severity of skin tumors, which could be reversed by concomitant genetic knockout of c-Myc but not by knockout of p53 or p19Arf. Notably, in the absence of Mule, c-Myc/Miz1 transcriptional complexes accumulated, and levels of p21CDKN1A (p21) and p15INK4B (p15) were down-regulated. In vitro, Mule-deficient primary keratinocytes exhibited increased proliferation that could be reversed by Miz1 knockdown. Transfer of Mule-deficient transformed cells to nude mice resulted in enhanced tumor growth that again could be abrogated by Miz1 knockdown. Our data demonstrate in vivo that Mule suppresses Ras-mediated tumorigenesis by preventing an accumulation of c-Myc/Miz1 complexes that mediates p21 and p15 down-regulation.
Keywords:
Huwe1; Miz1; Mule; Ras; c-Myc; p21.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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9,10-Dimethyl-1,2-benzanthracene / pharmacology
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Animals
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Cell Transformation, Neoplastic* / genetics
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Cells, Cultured
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Cyclin-Dependent Kinase Inhibitor p15 / biosynthesis
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Cyclin-Dependent Kinase Inhibitor p15 / genetics
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Cyclin-Dependent Kinase Inhibitor p15 / metabolism*
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Cyclin-Dependent Kinase Inhibitor p16
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Cyclin-Dependent Kinase Inhibitor p21 / biosynthesis
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Cyclin-Dependent Kinase Inhibitor p21 / genetics
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Cyclin-Dependent Kinase Inhibitor p21 / metabolism*
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Down-Regulation*
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Female
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Genes, ras
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Keratinocytes / drug effects
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Keratinocytes / metabolism
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Keratinocytes / pathology
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Male
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Mice
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Mice, Knockout
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Nuclear Proteins / antagonists & inhibitors*
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Nuclear Proteins / deficiency
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism
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Oncogene Protein p21(ras) / antagonists & inhibitors
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Oncogene Protein p21(ras) / genetics
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Oncogene Protein p21(ras) / metabolism*
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Protein Inhibitors of Activated STAT / antagonists & inhibitors*
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Protein Inhibitors of Activated STAT / deficiency
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Protein Inhibitors of Activated STAT / genetics
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Protein Inhibitors of Activated STAT / metabolism
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Proto-Oncogene Proteins c-myc / antagonists & inhibitors*
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Proto-Oncogene Proteins c-myc / deficiency
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Proto-Oncogene Proteins c-myc / genetics
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Proto-Oncogene Proteins c-myc / metabolism
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Signal Transduction
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Skin Neoplasms / chemically induced
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Skin Neoplasms / genetics
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Skin Neoplasms / metabolism
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Skin Neoplasms / pathology
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Tetradecanoylphorbol Acetate / pharmacology
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Tumor Suppressor Protein p53
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Tumor Suppressor Proteins
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Ubiquitin-Protein Ligases / deficiency
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Ubiquitin-Protein Ligases / genetics
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Ubiquitin-Protein Ligases / metabolism*
Substances
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Cdkn2a protein, mouse
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Cyclin-Dependent Kinase Inhibitor p15
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Cyclin-Dependent Kinase Inhibitor p16
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Cyclin-Dependent Kinase Inhibitor p21
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Nuclear Proteins
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Protein Inhibitors of Activated STAT
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Proto-Oncogene Proteins c-myc
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Tumor Suppressor Protein p53
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Tumor Suppressor Proteins
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9,10-Dimethyl-1,2-benzanthracene
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Huwe1 protein, mouse
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Miz1 protein, mouse
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Ubiquitin-Protein Ligases
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Oncogene Protein p21(ras)
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Tetradecanoylphorbol Acetate