Human origin recognition complex is essential for HP1 binding to chromatin and heterochromatin organization

Prasanth, S. G., Shen, Z., Prasanth, K. V. , Stillman, B. (2010) Human origin recognition complex is essential for HP1 binding to chromatin and heterochromatin organization. Proceedings of the National Academy of Sciences of the United States of America, 107 (34). pp. 15093-8. ISSN 0027-8424

URL: http://www.ncbi.nlm.nih.gov/pubmed/20689044
DOI: 10.1073/pnas.1009945107

Abstract

The origin recognition complex (ORC) is a DNA replication initiator protein also known to be involved in diverse cellular functions including gene silencing, sister chromatid cohesion, telomere biology, heterochromatin localization, centromere and centrosome activity, and cytokinesis. We show that, in human cells, multiple ORC subunits associate with hetereochromatin protein 1 (HP1) alpha- and HP1beta-containing heterochromatic foci. Fluorescent bleaching studies indicate that multiple subcomplexes of ORC exist at heterochromatin, with Orc1 stably associating with heterochromatin in G1 phase, whereas other ORC subunits have transient interactions throughout the cell-division cycle. Both Orc1 and Orc3 directly bind to HP1alpha, and two domains of Orc3, a coiled-coil domain and a mod-interacting region domain, can independently bind to HP1alpha; however, both are essential for in vivo localization of Orc3 to heterochromatic foci. Direct binding of both Orc1 and Orc3 to HP1 suggests that, after the degradation of Orc1 at the G1/S boundary, Orc3 facilitates assembly of ORC/HP1 proteins to chromatin. Although depletion of Orc2 and Orc3 subunits by siRNA caused loss of HP1alpha association to heterochromatin, loss of Orc1 and Orc5 caused aberrant HP1alpha distribution only to pericentric heterochromatin-surrounding nucleoli. Depletion of HP1alpha from human cells also shows loss of Orc2 binding to heterochromatin, suggesting that ORC and HP1 proteins are mutually required for each other to bind to heterochromatin. Similar to HP1alpha-depleted cells, Orc2 and Orc3 siRNA-treated cells also show loss of compaction at satellite repeats, suggesting that ORC together with HP1 proteins may be involved in organizing higher-order chromatin structure and centromere function.

Item Type: Paper
Subjects: bioinformatics > genomics and proteomics > genetics & nucleic acid processing > DNA, RNA structure, function, modification > DNA replication
Investigative techniques and equipment > imaging > flourescence bleaching
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > DNA, RNA structure, function, modification > siRNA
CSHL Authors:
Communities: CSHL labs > Stillman lab
Highlight: Stillman, Bruce W.
Depositing User: CSHL Librarian
Date Deposited: 05 Oct 2011 13:39
Last Modified: 20 Jun 2017 16:32
PMCID: PMC2930523
Related URLs:
URI: http://repository.cshl.edu/id/eprint/15509

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