title: The Cdk1 complex plays a prime role in regulating N-myc phosphorylation and turnover in neural precursors.
abstract: Myc family transcription factors are destabilized by phosphorylation of a conserved amino-terminal GSK-3beta motif. In proliferating cerebellar granule neuron precursors (CGNPs), Sonic hedgehog signaling induces N-myc expression, and N-myc protein is stabilized by insulin-like growth factor-mediated suppression of GSK-3beta. N-myc phosphorylation-mediated degradation is a prerequisite for CGNP growth arrest and differentiation. We investigated whether N-myc phosphorylation and turnover are thus linked to cell cycle exit in primary mouse CGNP cultures and the developing cerebellum. We report that phosphorylation-induced turnover of endogenous N-myc protein in CGNPs increases during mitosis, due to increased priming phosphorylation of N-myc for GSK-3beta. The priming phosphorylation requires the Cdk1 complex, whose cyclin subunits are indirect Sonic hedgehog targets. These findings provide a mechanism for promoting growth arrest in the final cycle of neural precursor proliferation competency, or for resetting the cell cycle in the G1 phase, by destabilizing N-myc in mitosis.
authors.affiliation: Department of Pediatric Oncology, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Sarah K
authors.initials: SK
authors.lastname: Sjostrom
authors.forename: Greg
authors.initials: G
authors.lastname: Finn
authors.forename: William C
authors.initials: WC
authors.lastname: Hahn
authors.forename: David H
authors.initials: DH
authors.lastname: Rowitch
authors.forename: Anna Marie
authors.initials: AM
authors.lastname: Kenney
mesh_terms: D000818:Animals; D016203:CDC2 Protein Kinase / Q000502:physiology*; D002453:Cell Cycle / Q000502:physiology; D045744:Cell Line, Tumor; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism; D019925:Cyclin A / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D016193:G1 Phase; D005786:Gene Expression Regulation; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D051379:Mice; D008938:Mitosis; D009447:Neuroblastoma / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure; D010744:Phosphoric Monoester Hydrolases / Q000494:pharmacology; D010766:Phosphorylation; D016271:Proto-Oncogene Proteins c-myc / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: C534699:CCNB1 protein, human; C534700:Ccnb1 protein, mouse; D019925:Cyclin A; D019926:Cyclin B; D056744:Cyclin B1; C489427:MYC protein, human; C489428:Myc protein, mouse; D016271:Proto-Oncogene Proteins c-myc; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D016203:CDC2 Protein Kinase; D038362:Glycogen Synthase Kinase 3; D010744:Phosphoric Monoester Hydrolases