The timing of events in mitosis is critical to ensure accurate chromosome segregation and genomic stability. Critical to these timing events is the Anaphase Promoting Complex, an E3 ubiquitin ligase that directs the ordered destruction of cyclin A, the chromosome segregation regulator Securin, and cyclin B. The known controllers of APC activity are the components of the spindle assembly checkpoint and the zinc binding protein Emi1. Emi1 functions to restrain the APC in S and G, thereby allowing the accumulation of cyclins. Emi1 is transcriptionally activated in G1 by the cyclin D/Rb/E2F pathway and destroyed in early mitosis following phosphorylation specific binding of the SCFI3TrCP ubiquitin ligase.
One aim of this grant is to identify the critical events triggering Emi1 destruction including the kinases that trigger Emi 1 destruction. We have also begun to characterize a large number of Emi1 interacting proteins (kIPs) to better understand the network of regulation controlling the APC. Here, we find the protein encoded by the Evi5 oncogene interacts with Emi1 and functions upstream of Emi1 to direct the accumulation of both Emi1 and cyclin A. Evi5 is a frequent site of proviral insertion in mouse T-cell lymphomas and is mutated in human neuroblastoma. Additionally, it is highly expressed in a variety of tumors. The Evi5 protein is predicted to be a GTPase activating protein, but the GTPase remains unknown. We find that Evi5 is required for accumulation of Emi1 and cyclin A in early G1 and new evidence suggests that it may participate in steps regulating the post-ubiquitination delivery of ubiquitinated proteins to the proteasome. Thus, Evi5 may promote oncogenesis by a previously unknown mechanism.
Our aims here are to (1) define factors controlling Evi5 function at G1-S and in mitosis; (2) to identify the mechanism for Evi5 control of proteolysis; (3) to identify the critical small GTPase regulated by Evi5; and (4) to define the factors controlling Emi1 destruction in mitosis.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM073023-02
Application #
7020674
Study Section
Cell Development and Function Integrated Review Group (CDF)
Program Officer
Zatz, Marion M
Project Start
2005-03-01
Project End
2009-02-28
Budget Start
2006-03-01
Budget End
2007-02-28
Support Year
2
Fiscal Year
2006
Total Cost
$309,919
Indirect Cost
Name
Stanford University
Department
Pathology
Type
Schools of Medicine
DUNS #
009214214
City
Stanford
State
CA
Country
United States
Zip Code
94305
Loktev, Alexander V; Zhang, Qihong; Beck, John S et al. (2008) A BBSome subunit links ciliogenesis, microtubule stability, and acetylation. Dev Cell 15:854-65
Wu, Judy Qiju; Hansen, David V; Guo, Yanxiang et al. (2007) Control of Emi2 activity and stability through Mos-mediated recruitment of PP2A. Proc Natl Acad Sci U S A 104:16564-9
Hansen, David V; Pomerening, Joseph R; Summers, Matthew K et al. (2007) Emi2 at the crossroads: where CSF meets MPF. Cell Cycle 6:732-8
Westlake, Christopher J; Junutula, Jagath R; Simon, Glenn C et al. (2007) Identification of Rab11 as a small GTPase binding protein for the Evi5 oncogene. Proc Natl Acad Sci U S A 104:1236-41
Eldridge, Adam G; Loktev, Alexander V; Hansen, David V et al. (2006) The evi5 oncogene regulates cyclin accumulation by stabilizing the anaphase-promoting complex inhibitor emi1. Cell 124:367-80