The overall goal of the proposed research is to elucidate the mechanisms by which the PI 3-kinase/Akt/GSK-3 signaling pathway regulates cell growth and survival. Both Akt and GSK-3 phosphorylate multiple transcription factors, but the overall program of gene expression controlled by PI 3-kinase/Akt/GSK-3 signaling remains to be fully understood. During the past grant period, global expression profiling combined with computational/experimental analysis of transcription factor binding sites has been used to characterize gene regulation by PI 3-kinase/Akt/GSK-3 signaling, both following growth factor stimulation of quiescent cells and during the continuous proliferation of cells maintained in serum. These studies identified CREB as a key transcription factor targeted by GSK-3 in quiescent cells, and have further implicated members of the AP-1, NF?B and NFAT transcription factor families as GSK-3 targets. A distinct set of genes, enriched in regulators of programmed cell death, is controlled by continuous PI 3-kinase signaling in proliferating cells. Computational analysis of upstream regulatory regions combined with chromatin immunoprecipitation assays indicate that FOXO, NF?B and Myc/Mad/Max transcription factors play major roles in regulation of these genes. In addition, computational analysis of the 3'untranslated regions of their mRNAs suggests that mRNA turnover is also involved in gene regulation by PI 3-kinase signaling. These studies will be continued with the goal of elucidating the program of gene regulation controlled by PI 3-kinase/Akt/GSK-3 signaling, including regulation of mRNA stability. The proposed experiments will proceed according to the following specific aims. 1. Characterization of the transcriptional program regulated by GSK-3 in quiescent cells. The roles of AP-1, NF?B and NFAT transcription factors will be investigated by chromatin immunoprecipitation and RNA interference. Computational analysis will be expanded to identify transcription factor binding sites in predicted enhancers as well as promoter regions, and the role of GSK-3 in regulation of delayed primary response as well as immediate-early genes will be studied. 2. Transcriptional regulation by PI 3-kinase/Akt/GSK-3 signaling in proliferating cells. RNA interference and transient transfection assays will be used to determine the roles of FOXO, NF?B and Myc/Mad/Max transcription factors in PI 3-kinase-dependent gene expression in proliferating cells. The role of GSK-3 in gene regulation during cell proliferation will also be investigated. 3. Regulation of mRNA stability. The role of mRNA degradation in gene regulation by PI 3-kinase will be investigated by determining the effect of PI 3-kinase/Akt/GSK-3 signaling on the stability of mRNAs that are down-regulated following inhibition of PI 3-kinase. Narrative Mutations affecting the PI 3-kinase/Akt/GSK-3 signaling pathway are among the most common abnormalities leading to the development of human cancer, and components of this pathway are active targets for drug development. The present proposal seeks to further understand the mechanism by which this pathway regulates cell survival. Discoveries of novel targets of PI 3-kinase signaling may provide new targets for cancer treatment.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA018689-36
Application #
8254440
Study Section
Cellular Signaling and Regulatory Systems Study Section (CSRS)
Program Officer
Salnikow, Konstantin
Project Start
1976-06-30
Project End
2014-04-30
Budget Start
2012-05-01
Budget End
2014-04-30
Support Year
36
Fiscal Year
2012
Total Cost
$471,832
Indirect Cost
$181,474
Name
Boston University
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
049435266
City
Boston
State
MA
Country
United States
Zip Code
02215
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Nayak, G; Cooper, G M (2012) p53 is a major component of the transcriptional and apoptotic program regulated by PI 3-kinase/Akt/GSK3 signaling. Cell Death Dis 3:e400
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Graham, Julie R; Hendershott, Melissa C; Terragni, Jolyon et al. (2010) mRNA degradation plays a significant role in the program of gene expression regulated by phosphatidylinositol 3-kinase signaling. Mol Cell Biol 30:5295-305
Saxena, Utsav H; Owens, Laura; Graham, Julie R et al. (2010) Prolyl isomerase Pin1 regulates transcription factor LSF (TFCP2) by facilitating dephosphorylation at two serine-proline motifs. J Biol Chem 285:31139-47
Saxena, Utsav H; Powell, Christina M H; Fecko, Jill K et al. (2009) Phosphorylation by cyclin C/cyclin-dependent kinase 2 following mitogenic stimulation of murine fibroblasts inhibits transcriptional activity of LSF during G1 progression. Mol Cell Biol 29:2335-45

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