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Molecular and Cellular Biology, November 2007, p. 7955-7965, Vol. 27, No. 22
0270-7306/07/$08.00+0 doi:10.1128/MCB.00908-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
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Department of Tumor Biology and Angiogenesis, Genentech Inc., 1 DNA way, South San Francisco, California 94080,1 Department of Pathology, Stanford University School of Medicine, Stanford, California 943052
Received 22 May 2007/ Returned for modification 25 June 2007/ Accepted 4 September 2007
Expression of the anaphase-promoting complex/cyclosome (APC/C) inhibitor Emi1 is required for the accumulation of APC/C substrates crucial for DNA synthesis and mitotic entry. We show that in vivo Emi1 expression correlates with the proliferative status of the cellular compartment and that cells lacking Emi1 undergo cellular senescence. Emi1 depletion leads to strong decreases in E2F target mRNA and APC/C substrate protein abundances. However, cyclin E mRNA and cyclin E protein levels and associated kinase activities are increased. Cells lacking Emi1 undergo DNA damage, likely explained by replication stress upon deregulated cyclin E- and A-associated kinase activities. Inhibition of ATM kinase prevents induction of senescence, implying that senescence is a consequence of DNA damage. Surprisingly, no senescence or no extensive amount of senescence is evident upon depletion of the Emi1-stabilizing factor Evi5 or Pin1, respectively. Our data suggest that maintenance of a protein stabilization/mRNA expression positive-feedback circuit fueled by Emi1 is required for accurate cell cycle progression, maintenance of DNA integrity, and prevention of cellular senescence.
Published ahead of print on 17 September 2007.
Supplemental material for this article may be found at http://mcb.asm.org/.
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