title: Architecture of the human origin recognition complex.
abstract: All the human homologs of the six subunits of Saccharomyces cerevisiae origin recognition complex have been reported so far. However, not much has been reported on the nature and the characteristics of the human origin recognition complex. In an attempt to purify recombinant human ORC from insect cells infected with baculoviruses expressing HsORC subunits, we found that human ORC2, -3, -4, and -5 form a core complex. HsORC1 and HsORC6 subunits did not enter into this core complex, suggesting that the interaction of these two subunits with the core ORC2-5 complex is extremely labile. We found that the C-terminal region of ORC2 interacts directly with the N-terminal region of ORC3. The C-terminal region of ORC3 was, however, necessary to bring ORC4 and ORC5 into the core complex. A fragment containing the N-terminal 200 residues of ORC3 (ORC3N) competitively inhibited the ORC2-ORC3 interaction. Overexpression of this fragment in U2OS cells blocked the cells in G(1), providing the first evidence that a mammalian ORC subunit is important for the G(1)-S transition in mammalian cells.
authors.affiliation: Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: S K
authors.initials: SK
authors.lastname: Dhar
authors.forename: L
authors.initials: L
authors.lastname: Delmolino
authors.forename: A
authors.initials: A
authors.lastname: Dutta
mesh_terms: D000818:Animals; D016367:Baculoviridae; D002352:Carrier Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D002460:Cell Line; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D007313:Insecta; D046911:Macromolecular Substances; D008958:Models, Molecular; D051738:Origin Recognition Complex; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D018411:Spodoptera; D014162:Transfection
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; C497224:ORC2 protein, human; C497225:ORC3 protein, human; C109152:ORC4 protein, human; C497226:ORC5 protein, human; D051738:Origin Recognition Complex; D021122:Protein Subunits; D011994:Recombinant Proteins