MCB
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Li, C.-J.
Right arrow Articles by DePamphilis, M. L.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Li, C.-J.
Right arrow Articles by DePamphilis, M. L.

 Previous Article  |  Next Article 

Molecular and Cellular Biology, January 2002, p. 105-116, Vol. 22, No. 1
0270-7306/01/$04.00+0     DOI: 10.1128/MCB.22.1.105-116.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Mammalian Orc1 Protein Is Selectively Released from Chromatin and Ubiquitinated during the S-to-M Transition in the Cell Division Cycle

Cong-Jun Li and Melvin L. DePamphilis*

National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-2753

Received 19 July 2001/ Returned for modification 30 August 2001/ Accepted 2 October 2001

Previous studies have shown that changes in the affinity of the hamster Orc1 protein for chromatin during the M-to-G1 transition correlate with the activity of hamster origin recognition complexes (ORCs) and the appearance of prereplication complexes at specific sites. Here we show that Orc1 is selectively released from chromatin as cells enter S phase, converted into a mono- or diubiquitinated form, and then deubiquitinated and re-bound to chromatin during the M-to-G1 transition. Orc1 is degraded by the 26S proteasome only when released into the cytosol, and peptide additions to Orc1 make it hypersensitive to polyubiquitination. In contrast, Orc2 remains tightly bound to chromatin throughout the cell cycle and is not a substrate for ubiquitination. Since the concentration of Orc1 remains constant throughout the cell cycle, and its half-life in vivo is the same as that of Orc2, ubiquitination of non-chromatin-bound Orc1 presumably facilitates the inactivation of ORCs by sequestering Orc1 during S phase. Thus, in contrast to yeast (Saccharomyces cerevisiae and Schizosaccharomyces pombe), mammalian ORC activity appears to be regulated during each cell cycle through selective dissociation and reassociation of Orc1 from chromatin-bound ORCs.

* Corresponding author. Mailing address: National Institute of Child Health and Human Development, Building 6, Room 416, National Institutes of Health, Bethesda, MD 20892-2753. Phone: (301) 402-8234. Fax: (301) 480-9354. E-mail: depamphm{at}box-d.nih.gov.

Molecular and Cellular Biology, January 2002, p. 105-116, Vol. 22, No. 1
0022-538X/01/$04.00+0     DOI: 10.1128/MCB.22.1.105-116.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
J. Bacteriol. J. Virol. Eukaryot. Cell
Microbiol. Mol. Biol. Rev. Clin. Vaccine Immunol. All ASM Journals

Copyright © 2002 by the American Society for Microbiology. All rights reserved.