Transcription factors p53 and E2F-1 coordinate and mediate apoptosis in response to genotoxic stress. However, the mechanism whereby how p53 and E2F-1 mediate apoptosis is unclear. We found that p53 and E2F-1 co-regulate the expression of ECK, an epithelial cell receptor protein-tyrosine kinase and that ECK mediates apoptosis following oxidative stress. In p53 inducible systems, ECK is greatly upregulated upon the activation of p53. The expression of ECK is increased following oxidative stress in a p53-dependent manner. We have cloned the promoter region of human ECK gene and identified two potential p53-binding sites within a 700 bp from the transcriptional initiation site of ECK. We show that p53 greatly induces luciferase activity of the luciferase reporter containing this sequence upstream of the luciferase gene. Interestingly, there is also an E2F-binding site in the ECK promoter. Cotransfection of E2F-1 with the luciferase reporter containing the potential E2F-1 binding site leads to the activation of this promoter reporter. We further demonstrate that the ectopic expression of E2F-1 elevates the levels of ECK protein. Finally, overexpression of ECK greatly increases cellular susceptibility to apoptosis and suppresses colony formation in soft agar. Our findings indicate that p53 and E2F-1 are transcriptional regulators of ECK and that ECK is a cell death receptor in the p53 and E2F-1 pathways. This is the first evidence that p53 and E2F-1 share a common target gene in signaling apoptosis. In this grant application, we propose a series of experimental approaches to classify ECK as a new member of the p53-downstream gene family and a dual target for p53 and E2F-1. We will determine whether and how ECK is regulated by these two fundamental tumor suppressors. We will demonstrate the importance of ECK in signaling oxidative cell death by apoptosis and its potential role in tumorigenesis. Successful achievement of our specific aims will provide evidence for how p53 and E2F-1 cooperatively regulate a protein receptor, which receives damage signals and mediates cell death. Characterization of ECK as a cell death receptor may reveal a new target for gene therapy or lead to the development of effective chemotherapeutical strategies in cancer treatment.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA093677-03
Application #
6693806
Study Section
Cell Development and Function Integrated Review Group (CDF)
Program Officer
Blair, Donald G
Project Start
2002-01-18
Project End
2005-12-31
Budget Start
2004-01-01
Budget End
2004-12-31
Support Year
3
Fiscal Year
2004
Total Cost
$291,030
Indirect Cost
Name
Columbia University (N.Y.)
Department
Radiation-Diagnostic/Oncology
Type
Schools of Medicine
DUNS #
621889815
City
New York
State
NY
Country
United States
Zip Code
10032
Wang, Jianli; Liu, Yu-Xin; Hande, M Prakash et al. (2007) TAp73 is a downstream target of p53 in controlling the cellular defense against stress. J Biol Chem 282:29152-62
Shen, Wen Hong; Balajee, Adayabalam S; Wang, Jianli et al. (2007) Essential role for nuclear PTEN in maintaining chromosomal integrity. Cell 128:157-70
Wang, Jianli; Yin, David P; Liu, Yu-Xin et al. (2007) Dual specificity phosphatase 1/CL100 is a direct transcriptional target of E2F-1 in the apoptotic response to oxidative stress. Cancer Res 67:6737-44
Jin, Y Jenny; Wang, Jianli; Qiao, Changhong et al. (2006) A novel mechanism for p53 to regulate its target gene ECK in signaling apoptosis. Mol Cancer Res 4:769-78