title: The brain-specific activator p35 allows Cdk5 to escape inhibition by p27Kip1 in neurons.
abstract: Cell cycle withdrawal in postmitotic cells involves cyclin-dependent kinase (Cdk) inhibitors that repress cell cycle Cdk activity. During mouse neurogenesis, cortical postmitotic neurons are shown here to accumulate high levels of the p27 Cdk inhibitor compared with their progenitor neuroblasts. Elevated p27 levels in staged embryo brain extracts correlate with p27 binding to Cdk2, and Cdk inactivation. Yet, Cdk5, which is associated with the noncyclin activator p35 in neurons, remains active in the presence of high p27 levels. Both in vitro and in vivo, p27 and related inhibitors can recognize a cyclin D-Cdk5 complex but not a p35-Cdk5 complex. The results indicate that the choice of activator determines the susceptibility of Cdk5 to p27 and related Cdk inhibitors, and thus its ability to act in postmitotic cells.
authors.affiliation: Cell Biology and Genetics Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
authors.forename: M H
authors.initials: MH
authors.lastname: Lee
authors.forename: M
authors.initials: M
authors.lastname: Nikolic
authors.forename: C A
authors.initials: CA
authors.lastname: Baptista
authors.forename: E
authors.initials: E
authors.lastname: Lai
authors.forename: L H
authors.initials: LH
authors.lastname: Tsai
authors.forename: J
authors.initials: J
authors.lastname: Massagué
mesh_terms: D000818:Animals; D001921:Brain / Q000196:embryology / Q000378:metabolism*; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D051360:Cyclin-Dependent Kinase 5; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases; D005260:Female; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D011247:Pregnancy; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D025521:Tumor Suppressor Proteins
chemical_list: C493961:Cdkn1b protein, mouse; C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; D025521:Tumor Suppressor Proteins; C089495:neuronal Cdk5 activator (p25-p35); D050760:Cyclin-Dependent Kinase Inhibitor p27; D051360:Cyclin-Dependent Kinase 5; D017346:Protein Serine-Threonine Kinases; C495906:Cdk5 protein, mouse; C495907:Cdk5 protein, rat; D018844:Cyclin-Dependent Kinases