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Proc Natl Acad Sci U S A. 2008 Jul 29;105(30):10326-31. doi: 10.1073/pnas.0803829105. Epub 2008 Jul 22.

The architecture of the DNA replication origin recognition complex in Saccharomyces cerevisiae.

Author information

1
Biology Department, Brookhaven National Laboratory, Upton, NY 11973, USA.

Abstract

The origin recognition complex (ORC) is conserved in all eukaryotes. The six proteins of the Saccharomyces cerevisiae ORC that form a stable complex bind to origins of DNA replication and recruit prereplicative complex (pre-RC) proteins, one of which is Cdc6. To further understand the function of ORC we recently determined by single-particle reconstruction of electron micrographs a low-resolution, 3D structure of S. cerevisiae ORC and the ORC-Cdc6 complex. In this article, the spatial arrangement of the ORC subunits within the ORC structure is described. In one approach, a maltose binding protein (MBP) was systematically fused to the N or the C termini of the five largest ORC subunits, one subunit at a time, generating 10 MBP-fused ORCs, and the MBP density was localized in the averaged, 2D EM images of the MBP-fused ORC particles. Determining the Orc1-5 structure and comparing it with the native ORC structure localized the Orc6 subunit near Orc2 and Orc3. Finally, subunit-subunit interactions were determined by immunoprecipitation of ORC subunits synthesized in vitro. Based on the derived ORC architecture and existing structures of archaeal Orc1-DNA structures, we propose a model for ORC and suggest how ORC interacts with origin DNA and Cdc6. The studies provide a basis for understanding the overall structure of the pre-RC.

PMID:
18647841
PMCID:
PMC2480615
DOI:
10.1073/pnas.0803829105
[Indexed for MEDLINE]
Free PMC Article

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