title: Phosphorylation of ORC2 protein dissociates origin recognition complex from chromatin and replication origins.
abstract: During the late M to the G(1) phase of the cell cycle, the origin recognition complex (ORC) binds to the replication origin, leading to the assembly of the prereplicative complex for subsequent initiation of eukaryotic chromosome replication. We found that the cell cycle-dependent phosphorylation of human ORC2, one of the six subunits of ORC, dissociates ORC2, -3, -4, and -5 (ORC2-5) subunits from chromatin and replication origins. Phosphorylation at Thr-116 and Thr-226 of ORC2 occurs by cyclin-dependent kinase during the S phase and is maintained until the M phase. Phosphorylation of ORC2 at Thr-116 and Thr-226 dissociated the ORC2-5 from chromatin. Consistent with this, the phosphomimetic ORC2 protein exhibited defective binding to replication origins as well as to chromatin, whereas the phosphodefective protein persisted in binding throughout the cell cycle. These results suggest that the phosphorylation of ORC2 dissociates ORC from chromatin and replication origins and inhibits binding of ORC to newly replicated DNA.
authors.affiliation: Department of Biological Sciences, Seoul National University, Seoul 151-742, Korea.
authors.forename: Kyung Yong
authors.initials: KY
authors.lastname: Lee
authors.forename: Sung Woong
authors.initials: SW
authors.lastname: Bang
authors.forename: Sang Wook
authors.initials: SW
authors.lastname: Yoon
authors.forename: Seung-Hoon
authors.initials: SH
authors.lastname: Lee
authors.forename: Jong-Bok
authors.initials: JB
authors.lastname: Yoon
authors.forename: Deog Su
authors.initials: DS
authors.lastname: Hwang
mesh_terms: D000595:Amino Acid Sequence; D002843:Chromatin / Q000378:metabolism*; D017124:Conserved Sequence; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D051738:Origin Recognition Complex / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D010769:Phosphothreonine / Q000378:metabolism; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D018741:Replication Origin; D016196:S Phase
chemical_list: D002843:Chromatin; C497224:ORC2 protein, human; D051738:Origin Recognition Complex; D010769:Phosphothreonine