Mammalian Atypical E2fs Link Endocycle Control to Cancer
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Mammalian Atypical E2Fs Link Endocycle Control to Cancer DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Hui-Zi Chen Graduate Program in Integrated Biomedical Science Program The Ohio State University 2011 Dissertation Committee: Gustavo Leone, PhD, Advisor Michael Ostrowski, PhD Clay Marsh, MD Tsonwin Hai, PhD Kathryn Wikenheiser-Brokamp, MD PhD Copyright by Hui-Zi Chen 2011 Abstract The endocycle is a developmentally programmed variant cell cycle consisting of successive S (DNA synthesis) and G (Gap) phases without an intervening M phase or cytokinesis. As a consequence of the regulated “decoupling” of DNA replication and mitosis, which are two central processes of the traditional cell division program, endocycling cells acquire highly polyploid genomes after having undergone multiple rounds of whole genome reduplication. Although essential for metazoan development, relatively little is known about the regulation of endocycle or its physiologic role in higher vertebrates such as the mammal. A substantial body of work in the model organism Drosophila melanogaster has demonstrated an important function for dE2Fs in the control of endocycle. Genetic studies showed that both endocycle initiation and progression is severely disrupted by altering the expression of the fly E2F activator (dE2F1) or repressor (dE2F2). In mammals, the E2F family is comprised of nine structurally related proteins, encoded by eight distinct genes, that can be classified into transcriptional activators (E2f1, E2f2, E2f3a and E2f3b) or repressors (E2f4, E2f5, E2f6, E2f7 and E2f8). The repressor subclass may then be further divided into canonical (E2f4, E2f5 and E2f6) or atypical E2fs (E2f7 and E2f8). Until this study, there has been sparse knowledge regarding the role of E2fs in ii the control of mammalian endocycle, or what the physiologic consequences might be of perturbed endocycles in tissues composed of polyploid cells such as the liver. Now using a combination of novel and established lineage-specific cre mice we identified that two opposing arms of the E2F program, one driven by canonical transcription activation (E2F1, E2F2 and E2F3) and the other by atypical repression (E2F7 and E2F8), converge on the regulation endocycles in vivo. Ablation of canonical activators in the two endocycling tissues of mammals, trophoblast giant cells (TGCs) in the placenta and hepatocytes in the liver, augmented genome ploidy, whereas ablation of atypical repressors diminished ploidy. Surprisingly, the severe reduction of ploidy caused by E2f7/E2f8 deficiency had no apparent adverse impact on placental and hepatic physiology. However, the sole inactivation of E2f8 in hepatocytes, which biases toward a diploid state, resulted in the development of spontaneous hepatocellular carcinoma (HCC). Loss of E2f8 also potentiated the development of carcinogen-induced HCC, suggesting that E2F8 functions to suppress tumor initiation and impede tumor progression. Taken together, the results presented within provide the first in vivo evidence for a direct role of E2Fs in regulating non-traditional cell cycles in mammals and genetically link endocycle control with cancer. iii Dedication This thesis is dedicated to my family, with immense love and gratitude. This is also dedicated to Dr. Allan Yates, whose kindness changed the course of my life in more ways than one. iv Acknowledgments A tremendous thank you to my dissertation committee members and my adivsor, for your contributions to my scientific footprints. I would be gracious to have your continued support as I now forge ahead, creating new paths. Also a sincere thank you to IBGP and MSTP directors and administrators for your guidance and support. To all members (past, present and future) of the Leone laboratory: I could not have made it through without your infinite wisdom and anecdotes, which indelibly contributed to my scientific growth and, perhaps more importantly, my growth as an individual (you have been like a family). v Vita 1997 - 2001 ................................................. Upper Arlington High School Columbus, OH 2001 - 2005 ................................................. B.A. Molecular and Cellular Biology College of Arts and Sciences Cornell University, Ithaca, NY 2005 - 2007 ................................................. Medical Student College of Medicine The Ohio State University, Columbus, OH 2007 - present ............................................. Graduate Research Associate College of Medicine The Ohio State University, Columbus, OH Publications 1. Chen, H.-Z.*, Ouseph, M.M.*, Li, J., Pecot, T., Liu, B., Chokshi, V., Byrne, M., Duran, C., Comstock, G., Martin, C.K., Trikha, P., Senapati, S., Huang, Y.-W., Gandhi, S., Wilson, N.B., Thompson, J.C., Raman, S., Singh, S., Leone, M., Machiraju, R., Huang, K., Mo, X., Fernandez, S., Wolgemuth, D.J., Sicinski, P., Huang, T., Jin, V., and Leone, G. Atypical E2Fs link Mammalian Endocycle Control to Cancer. Submitted. 2. Ouseph, M.M.*, Li, J.*, Chen, H.-Z., Pecot, T., Wenzel, P., Thompson, J.C., Comstock, G., Chokshi, V., Byrne, M., Forde, B., Chong, J.-L., Huang, K., Machiraju, R., and Leone, G. Atypical E2F repressors and activators coordinate Placental Development. Submitted. vi 3. Wang, H., Chen, H.-Z., Wu, L., de Bruin, A., House, M., Ng, S., Johnson, J., Goldenberg, L.E., Fang, X., Fernandez, S.A., Stephens, J.A., Naidu, S., Stromberg, P., Rosol, T.J., Shapiro, C.L., and Leone, G. Suppression of anti-tumor immunity by E2F3. In preparation. 4. Wenzel, P., Chong, J.-L., Sáenz-Robles, M.T., Ferrey, A., Hagan, J.P., Gomez, Y.M., Rajmohan. R., Sharma, N., Chen, H.-Z., Pipas, J.M., Robinson, M.L., and Leone, G. (2011). Mammalian cell proliferation in the absence of E2F1-3. Dev. Biol. 315, 35- 45. 5. Wang, H., Karikomi, M., Naidu, S., Rajmohan, R., Caserta, E., Chen, H.-Z., Rawahneh, M., Moffitt, J., Stephens, J.A., Fernandez, S.A., Weinstein, M., La Perle, K., Stromberg, P., Rosol, T.J., Eng, C., Ostrowski, M., and Leone, G. (2010). Allele- specific tumor spectrum in Pten knockin mice. Proc. Natl. Acad. Sci. USA 107, 5142-5147. 6. Martinez, L.A., Goluszko, E., Chen, H.-Z., Leone, G., Post, S.M., Lozano, G., Chen, Z., and Chauchereau, A. (2010). E2F3a is a mediator of DNA damage induced apoptosis. Mol. Cell. Biol. 30, 524-536. 7. Chen, H.-Z., Tsai, S.-Y., and Leone, G. (2009). Emerging roles of E2Fs in cancer: an exit from cell cycle control. Nat. Rev. Cancer 11, 785-797. 8. Chong, J.-L., Wenzel, P., Sáenz-Robles, M.T., Nair, V., Ferrey, A., Hagan, J.P. Gomez, Y.M., Sharma, N., Chen, H.-Z., Ouseph, M., Wang, S.-H., Culp, B., Mezache, L., Winton, D.J., Sansom, O.J., Cantalupo, P.G., Robinson, M.L., Pipas, J.M., and Leone, G. (2009). A switch of E2F1-3 function from activators in progenitor cells to repressors in differentiating cells. Nature 462, 930-934. 9. Li, J., Ran, C., Gordon, F., Comstock, G., Siddiqui, H., Cleghorn, W., Chen, H.-Z., Kornacker, K., Liu, C.G., Pandit, S.K., Khanizadeh, M., Weinstein, M., Leone, G., and de Bruin, A. (2008). Synergistic function of E2F7 and E2F8 is essential for cell survival and embryonic development. Dev. Cell 14, 62-75. 10. Wang, D., Chen, H., Momary, K.M., Cavallari, L.H., Johnson, J.A., and Sadee, W. (2008). Regulatory polymorphism in vitamin K epoxide reductase complex subunit 1 (VKORC1) affects gene expression and warfarin dose requirement. Blood 112, 1013- 1021. 11. Zhang, X., Chen, X., Song, H., Chen, H.-Z., and Rovin, B.H. (2005). Activation of the Nrf2/antioxidant response pathway increases IL-8 expression. Eur. J. Immunol. 35, 3258-3267. vii 12. Zhang, X., Chen, H.-Z., and Rovin, B.H. (2003). Unexpected sensitivity of synthetic Renilla luciferase control vectors to treatment with a cyclopentenone prostaglandin. Biotechniques 35, 1144-1148. Fields of Study Major Field: Integrated Biomedical Science Program viii Table of Contents Abstract .......................................................................................................................... ii Dedication ..................................................................................................................... iv Acknowledgments ...........................................................................................................v Vita ............................................................................................................................... vi List of Tables................................................................................................................ xii List of Figures ............................................................................................................. xiii Chapter 1: General Introduction .................................................................................1 1.1. Role of E2Fs in Cell Cycle Regulation: The Classic Paradigm.......................1 1.2. The Endocycle: Variant Cell Cycle with a Purpose ..................................... 15 Chapter 2: Role of Mammalian E2F Activators in Endocycle Control ..................... 22 2.1. Introduction ................................................................................................. 22 2.2. Results ........................................................................................................ 23 2.3. Discussion ................................................................................................... 24 2.4. Materials and methods ................................................................................