title: Myc-enhanced expression of Cul1 promotes ubiquitin-dependent proteolysis and cell cycle progression.
abstract: The c-Myc oncoprotein plays an important role in the growth and proliferation of normal and neoplastic cells. To execute these actions, c-Myc is thought to regulate functionally diverse sets of genes that directly govern cellular mass and progression through critical cell cycle transitions. Here, we provide several lines of evidence that c-Myc promotes ubiquitin-dependent proteolysis by directly activating expression of the Cul1 gene, encoding a critical component of the ubiquitin ligase SCF(SKP2). The cell cycle inhibitor p27(kip1) is a known target of the SCF(SKP2) complex, and Myc-induced Cul1 expression matched well with the kinetics of declining p27(kip1) protein. Enforced Cul1 expression or antisense neutralization of p27(kip1) was capable of overcoming the slow-growth phenotype of c-Myc null primary mouse embryonic fibroblasts (MEFs). In reconstitution assays, the addition of in vitro translated Cul1 protein alone was able to restore p27(kip1) ubiquitination and degradation in lysates derived from c-myc(-/-) MEFs or density-arrested human fibroblasts. These functional and biochemical data provide a direct link between c-Myc transcriptional regulation and ubiquitin-mediated proteolysis and together support the view that c-Myc promotes G(1) exit in part via Cul1-dependent ubiquitination and degradation of the CDK inhibitor, p27(kip1).
authors.affiliation: Department of Adult Oncology, Dana Farber Cancer Institute, Boston, Massachusetts 02115, USA.
authors.forename: R C
authors.initials: RC
authors.lastname: O'Hagan
authors.forename: M
authors.initials: M
authors.lastname: Ohh
authors.forename: G
authors.initials: G
authors.lastname: David
authors.forename: I M
authors.initials: IM
authors.lastname: de Alboran
authors.forename: F W
authors.initials: FW
authors.lastname: Alt
authors.forename: W G
authors.initials: WG
authors.lastname: Kaelin
authors.forename: R A
authors.initials: RA
authors.lastname: DePinho
mesh_terms: D016475:3T3 Cells; D000818:Animals; D015152:Blotting, Northern; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D002455:Cell Division; D044842:Cullin Proteins; D019925:Cyclin A / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D015151:Immunoblotting; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D010453:Peptide Synthases / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D012190:Retroviridae / Q000235:genetics; D016196:S Phase; D044843:SKP Cullin F-Box Protein Ligases; D013997:Time Factors; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins; D014452:Ubiquitins / Q000378:metabolism*
chemical_list: C105153:CUL2 protein, human; C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D044842:Cullin Proteins; D019925:Cyclin A; D008869:Microtubule-Associated Proteins; D016271:Proto-Oncogene Proteins c-myc; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D014452:Ubiquitins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D008156:Luciferases; D044843:SKP Cullin F-Box Protein Ligases; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D010453:Peptide Synthases