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Updated: Mar 11, 2026

Generation and Purification of Human INO80 Chromatin Remodeling Complexes and Subcomplexes
Published on: October 23, 2014
Two subunits of human ORC are dispensable for DNA replication and proliferation
Etsuko Shibata1, Manjari Kiran1, Yoshiyuki Shibata1
1Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, United States.
Abstract:
The six-subunit Origin Recognition Complex (ORC) is believed to be an essential eukaryotic ATPase that binds to origins of replication as a ring-shaped heterohexamer to load MCM2-7 and initiate DNA replication. We have discovered that human cell lines in culture proliferate with intact chromosomal origins of replication after disruption of both alleles of ORC2 or of the ATPase subunit, ORC1. The ORC1 or ORC2-depleted cells replicate with decreased chromatin loading of MCM2-7 and become critically dependent on another ATPase, CDC6, for survival and DNA replication. Thus, either the ORC ring lacking a subunit, even its ATPase subunit, can load enough MCM2-7 in partnership with CDC6 to initiate DNA replication, or cells have an ORC-independent, CDC6-dependent mechanism to load MCM2-7 on origins of replication.
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