Abstract
Notch genes encode a family of transmembrane proteins that are involved in many cellular processes such as differentiation, proliferation, and apoptosis. Although it is well established that all four Notch genes can act as oncogenes, the mechanism by which Notch proteins transform cells remains unknown. Previously, we have shown that transformation of RKE cells can be conditionally induced by hormone activation of Notch(ic)-estrogen receptor (ER) chimeras. Using this inducible system, we show that Notch(ic) activates transcription of the cyclin D1 gene with rapid kinetics. Transcriptional activation of cyclin D1 is independent from serum-derived growth factors and de novo synthesis of secondary transcriptional activators. Moreover, hormone activation of Notch(ic)-ER proteins induces CDK2 activity in the absence of serum. Upregulation of cyclin D1 and activation of CDK2 by Notch(ic) result in the promotion of S-phase entry. These data demonstrate the first evidence that Notch(ic) proteins can directly regulate factors involved in cell cycle control and affect cellular proliferation. Furthermore, nontransforming Notch(ic) proteins do not induce cyclin D1 expression, indicating that the mechanism of transformation involves cell cycle deregulation through constitutive expression of cyclin D1. Finally, we have identified a CSL [stands for CBF1, Su(H), and Lag-1] binding site within the human and rat cyclin D1 promoters, suggesting that Notch(ic) proteins activate cyclin D1 transcription through a CSL-dependent pathway.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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CDC2-CDC28 Kinases*
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Cell Cycle
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Cell Line, Transformed
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Chemokine CCL4
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Chemokines, CC
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Cyclin D1 / genetics*
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Cyclin D1 / metabolism
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Cyclin-Dependent Kinase 2
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Cyclin-Dependent Kinases / metabolism*
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DNA-Binding Proteins / metabolism
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Drosophila Proteins*
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Enzyme Activation
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Humans
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Immunoglobulin J Recombination Signal Sequence-Binding Protein
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Macrophage Inflammatory Proteins
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Membrane Proteins / genetics
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Membrane Proteins / metabolism*
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Nuclear Proteins*
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Promoter Regions, Genetic
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Protein Serine-Threonine Kinases / metabolism*
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Proteins / metabolism
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RNA, Messenger
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Receptors, Cell Surface / genetics
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Receptors, Cell Surface / metabolism*
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Receptors, Estrogen / genetics
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Receptors, Estrogen / metabolism
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Receptors, Notch
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Repressor Proteins / metabolism
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Tamoxifen / analogs & derivatives*
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Tamoxifen / metabolism
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Transcriptional Activation*
Substances
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CCL4 protein, human
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Chemokine CCL4
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Chemokines, CC
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DNA-Binding Proteins
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Drosophila Proteins
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Immunoglobulin J Recombination Signal Sequence-Binding Protein
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Macrophage Inflammatory Proteins
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Membrane Proteins
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Nuclear Proteins
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Proteins
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RBPJ protein, human
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RNA, Messenger
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Receptors, Cell Surface
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Receptors, Estrogen
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Receptors, Notch
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Recombinant Fusion Proteins
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Repressor Proteins
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Su(H) protein, Drosophila
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Tamoxifen
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Cyclin D1
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afimoxifene
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Protein Serine-Threonine Kinases
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CDC2-CDC28 Kinases
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CDK2 protein, human
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Cyclin-Dependent Kinase 2
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Cyclin-Dependent Kinases