Human Orc2 localizes to centrosomes, centromeres and heterochromatin during chromosome inheritance

Prasanth, S. G., Prasanth, K. V. , Siddiqui, K., Spector, D. L., Stillman, B. (July 2004) Human Orc2 localizes to centrosomes, centromeres and heterochromatin during chromosome inheritance. EMBO J, 23 (13). pp. 2651-63. ISSN 0261-4189 (Print)

DOI: 10.1038/sj.emboj.7600255


The initiation of DNA replication in S phase requires the prior assembly of an origin recognition complex (ORC)-dependent pre-replicative complex on chromatin during G1 phase of the cell division cycle. In human cells, the Orc2 subunit localized to the nucleus as expected, but it also localized to centrosomes throughout the entire cell cycle. Furthermore, Orc2 was tightly bound to heterochromatin and heterochromatin protein 1alpha (HP1alpha) and HP1beta in G1 and early S phase, but during late S, G2 and M phases tight chromatin association was restricted to centromeres. Depletion of Orc2 by siRNA caused multiple phenotypes. A population of cells showed an S-phase defect with little proliferating cell nuclear antigen (PCNA) on chromatin, although MCM proteins remained. Orc2 depletion also disrupted HP1 localization, but not histone-H3-lysine-9 methylation at prominent heterochromatic foci. Another subset of Orc2-depleted cells containing replicated DNA arrested with abnormally condensed chromosomes, failed chromosome congression and multiple centrosomes. These results implicate Orc2 protein in chromosome duplication, chromosome structure and centrosome copy number control, suggesting that it coordinates all stages of the chromosome inheritance cycle.

Item Type: Paper
Uncontrolled Keywords: Apoptosis Cell Cycle Centromere metabolism Centrosome metabolism Chromatin metabolism Chromosomal Proteins Non-Histone metabolism Chromosomes genetics Cloning Molecular DNA Replication DNA-Binding Proteins drug effects genetics metabolism Flow Cytometry Fluorescent Antibody Technique Hela Cells Heterochromatin metabolism Humans Kinetics Metaphase Origin Recognition Complex Proliferating Cell Nuclear Antigen genetics metabolism RNA Small Interfering/pharmacology
Subjects: bioinformatics > genomics and proteomics > genetics & nucleic acid processing > protein structure, function, modification > protein types > origin recognition complex
CSHL Authors:
Communities: CSHL labs > Spector lab
CSHL labs > Stillman lab
Highlight: Stillman, Bruce W.
Depositing User: CSHL Librarian
Date: 7 July 2004
Date Deposited: 26 Jan 2012 18:09
Last Modified: 20 Jun 2017 18:16
PMCID: PMC449767
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