title: Cdc6-induced conformational changes in ORC bound to origin DNA revealed by cryo-electron microscopy.
abstract: The eukaryotic origin recognition complex (ORC) interacts with and remodels origins of DNA replication prior to initiation in S phase. Here, we report a single-particle cryo-EM-derived structure of the supramolecular assembly comprising Saccharomyces cerevisiae ORC, the replication initiation factor Cdc6, and double-stranded ARS1 origin DNA in the presence of ATPγS. The six subunits of ORC are arranged as Orc1:Orc4:Orc5:Orc2:Orc3, with Orc6 binding to Orc2. Cdc6 binding changes the conformation of ORC, in particular reorienting the Orc1 N-terminal BAH domain. Segmentation of the 3D map of ORC-Cdc6 on DNA and docking with the crystal structure of the homologous archaeal Orc1/Cdc6 protein suggest an origin DNA binding model in which the DNA tracks along the interior surface of the crescent-like ORC. Thus, ORC bends and wraps the DNA. This model is consistent with the observation that binding of a single Cdc6 extends the ORC footprint on origin DNA from both ends.
authors.affiliation: Biology Department, Brookhaven National Laboratory, Upton, NY 11973, USA.
authors.forename: Jingchuan
authors.initials: J
authors.lastname: Sun
authors.forename: Hironori
authors.initials: H
authors.lastname: Kawakami
authors.forename: Juergen
authors.initials: J
authors.lastname: Zech
authors.forename: Christian
authors.initials: C
authors.lastname: Speck
authors.forename: Bruce
authors.initials: B
authors.lastname: Stillman
authors.forename: Huilin
authors.initials: H
authors.lastname: Li
mesh_terms: D018797:Cell Cycle Proteins / Q000737:chemistry*; D020285:Cryoelectron Microscopy; D004268:DNA-Binding Proteins / Q000737:chemistry*; D008958:Models, Molecular; D051738:Origin Recognition Complex / Q000737:chemistry*; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry*; D014157:Transcription Factors / Q000737:chemistry*
chemical_list: C064055:ABFI protein, S cerevisiae; C066503:CDC6 protein, S cerevisiae; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C497214:ORC1 protein, S cerevisiae; D051738:Origin Recognition Complex; D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors