title: The binding of ORC2 to chromatin from terminally differentiated cells.
abstract: Nuclei from terminally differentiated Xenopus erythrocytes lack essential components of the prereplication complex, including the origin recognition complex (ORC) proteins XORC1 and XORC2. In Xenopus egg extract, these proteins are able to bind erythrocyte chromatin from permeable nuclei, but not from intact nuclei, even though they are able to cross an intact nuclear envelope. In this report we use both permeable and intact erythrocyte nuclei to investigate the role of cyclin-dependent kinase activity in modulating the binding of XORC2 to chromatin. We find that elevating the level of cyclin A-dependent kinase in egg extract prevents the binding of XORC2 to chromatin from permeable nuclei and that kinase inhibition reverses this effect. We also observe a nuclear transport-dependent accumulation of H1 kinase activity within intact nuclei incubated in the extract. However, inhibiting this kinase activity does not facilitate the binding of XORC2 to chromatin, suggesting that other molecules and/or mechanisms exist to prevent association of XORC proteins with replication origins within intact nuclei from terminally differentiated cells.
authors.affiliation: Department of Biochemistry, University of Mississippi Medical Center, 2500 North State Street, Jackson, Mississippi 39216, USA.
authors.forename: H
authors.initials: H
authors.lastname: Xu
authors.forename: Z H
authors.initials: ZH
authors.lastname: Lu
authors.forename: G H
authors.initials: GH
authors.lastname: Leno
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D042846:CDC2-CDC28 Kinases; D002454:Cell Differentiation / Q000235:genetics*; D002455:Cell Division / Q000502:physiology*; D002467:Cell Nucleus / Q000235:genetics*; D002843:Chromatin / Q000235:genetics / Q000378:metabolism*; D019925:Cyclin A / Q000378:metabolism / Q000494:pharmacology; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000378:metabolism / Q000494:pharmacology; D004261:DNA Replication / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004900:Erythroblasts / Q000378:metabolism*; D005260:Female; D006657:Histones / Q000378:metabolism; D016200:Maturation-Promoting Factor / Q000037:antagonists & inhibitors / Q000378:metabolism; D009685:Nuclear Envelope / Q000235:genetics / Q000378:metabolism; D009865:Oocytes; D051738:Origin Recognition Complex; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000494:pharmacology; D014981:Xenopus; D029867:Xenopus Proteins
chemical_list: D002843:Chromatin; D019925:Cyclin A; D004268:DNA-Binding Proteins; D006657:Histones; D051738:Origin Recognition Complex; D029867:Xenopus Proteins; D011494:Protein Kinases; C102333:histone H1 kinase; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495891:Cdk2 protein, Xenopus; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D016200:Maturation-Promoting Factor