Cdc6-induced conformational changes in ORC bound to origin DNA revealed by cryo-electron microscopy

Structure. 2012 Mar 7;20(3):534-44. doi: 10.1016/j.str.2012.01.011.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Cycle Proteins / chemistry*
  • Cryoelectron Microscopy
  • DNA-Binding Proteins / chemistry*
  • Models, Molecular*
  • Origin Recognition Complex / chemistry*
  • Protein Conformation*
  • Protein Subunits / chemistry
  • Saccharomyces cerevisiae Proteins / chemistry*
  • Transcription Factors / chemistry*

Substances

  • ABFI protein, S cerevisiae
  • CDC6 protein, S cerevisiae
  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • ORC1 protein, S cerevisiae
  • Origin Recognition Complex
  • Protein Subunits
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors