Depending upon particular cellular conditions, the tumor suppressor protein p53 induces growth arrest or mediates an apoptotic response. Inactivation of the apoptotic response, in particular, has been implicated in the process of oncogenesis as well as in the resistance of tumor cells to particular therapies. Since the DNA binding activity of p53 plays a role in each of the physiological responses to p53, the ability of p53 to select among various target genes to elicit a particular cellular response may be central to the regulation of its biological function. To date, the identification of a mechanism for the regulation of target gene selectivity by p53 has been elusive. The research that is proposed in this application is designed to test the hypothesis that the cellular response to p53 is determined by regulation of its target gene selectivity and that defects in the expression of particular target genes provide the molecular basis for defective p53-dependent apoptosis in tumor cells. Previous studies have shown differential p53-dependent regulation of a gene involved in growth arrest, the cyclin-dependent kinase inhibitor p21, as compared to one involved in apoptosis, bax. The molecular basis for this selectivity will be explored through three specific aims. First, since p53 binding sites in the p21 and bax promoters require additional gene-specific elements for robust p53-dependent transcriptional regulation, studies are proposed to elucidate the underlying mechanisms by which such cis-acting elements cooperate with particular p53 binding sites to affect transcription in a gene-specific manner. Two tumor-derived mutants had previously been identified which retain the ability to induce growth arrest but had selectively lost the capacity to trigger apoptosis. While the two mutants were capable of upregulating the p22 promoter, both showed defective activation of the bax promoter. In the second aim the activity of these two mutant p53 proteins will be examined to elucidate the basis for these promoter-specific effects. Three tumor cell lines have been identified in which p.53 efficiently upregulated the p21 promoter but showed defective activation of bax.
The third aim i s to determine the molecular basis for this differential regulations. The optimal therapeutic response to DNA damage caused by many chemotherapeutic agents is apoptosis rather than cell cycle arrest. Elucidating the molecular mechanisms that are responsible for the ability of p53 to trigger apoptosis versus arrest may lead to more effective therapeutic intervention and a way to overcome the chemotherapeutic-resistant phenotype found in many tumors.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA086001-03
Application #
6687815
Study Section
Pathology B Study Section (PTHB)
Program Officer
Blair, Donald G
Project Start
2002-01-01
Project End
2006-12-31
Budget Start
2004-01-01
Budget End
2004-12-31
Support Year
3
Fiscal Year
2004
Total Cost
$281,794
Indirect Cost
Name
Mount Sinai School of Medicine
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
078861598
City
New York
State
NY
Country
United States
Zip Code
10029
Senturk, Emir; Manfredi, James J (2013) p53 and cell cycle effects after DNA damage. Methods Mol Biol 962:49-61
Hamard, Pierre-Jacques; Manfredi, James J (2012) Mdm2's dilemma: to degrade or to translate p53? Cancer Cell 21:3-5
Chander, Harish; Halpern, Max; Resnick-Silverman, Lois et al. (2011) Skp2B overexpression alters a prohibitin-p53 axis and the transcription of PAPP-A, the protease of insulin-like growth factor binding protein 4. PLoS One 6:e22456
Resnick-Silverman, Lois; Manfredi, James J (2011) Analyzing p53 regulated DNA damage checkpoints by flow cytometry. Methods Mol Biol 782:193-203
Chander, Harish; Halpern, Max; Resnick-Silverman, Lois et al. (2010) Skp2B attenuates p53 function by inhibiting prohibitin. EMBO Rep 11:220-5
Manfredi, James J (2010) An identity crisis for a cancer gene: subcellular location determines ASPP1 function. Cancer Cell 18:409-10
Manfredi, James J (2010) The Mdm2-p53 relationship evolves: Mdm2 swings both ways as an oncogene and a tumor suppressor. Genes Dev 24:1580-9
Varmeh, Shohreh; Manfredi, James J (2009) Inappropriate activation of cyclin-dependent kinases by the phosphatase Cdc25b results in premature mitotic entry and triggers a p53-dependent checkpoint. J Biol Chem 284:9475-88
Giono, Luciana E; Manfredi, James J (2007) Mdm2 is required for inhibition of Cdk2 activity by p21, thereby contributing to p53-dependent cell cycle arrest. Mol Cell Biol 27:4166-78
Resnick-Silverman, Lois; Manfredi, James J (2006) Gene-specific mechanisms of p53 transcriptional control and prospects for cancer therapy. J Cell Biochem 99:679-89

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