نبذة مختصرة : c-Myc transformed human Burkitt's lymphoma (BL) cells are highly sensitive to TGF-β-induced apoptosis. Previously we demonstrated that TGF-β-mediated cell death in BL cells is regulated via the mitochondrial intrinsic apoptosis pathway, which is dependent on the activation of BAX and/or BAK. TGF-β directly induces transcription of the BH3-only protein BIK and represses expression of the pro-survival factor BCL-X(L) but has no effect on the direct BAX/BAK "activators" BIM or BID (tBID). Here we show that TGF-β induces the BH3-only activator PUMA to aid induction of the intrinsic cell death pathway. TGF-β also induced PUMA in normal germinal center CD77-positive centroblasts isolated from human tonsil tissue. PUMA was a direct TGF-β target gene in B-cells, and we identify a putative Smad-binding region within the human PUMA promoter that recruits Smad3 and Smad4 in cells in response to TGF-β signaling. Constitutive activity of the isolated Smad-binding region in luciferase reporter assays was dependent on Smad consensus sequences and was partially dependent on endogenous TGF-β signaling and Smad4. Knockdown of PUMA in BL cells using lentiviral shRNA resulted in slower kinetics of the TGF-β-mediated apoptotic response. Analysis of Eμ-Myc cell lines demonstrated that c-myc-driven murine lymphomas are also sensitive to TGF-β-mediated apoptosis. Moreover, Puma(-/-) Eμ-Myc lines demonstrated significantly delayed kinetics of the apoptotic response when compared with wild type lymphomas. TGF-β therefore induces a polygenic response in Myc-driven lymphomas involving transcription of PUMA, which is necessary for the rapid induction of cell death.
Relation: pii: S0021-9258(20)46323-9; Spender, L. C., Carter, M. J., O'Brien, D. I., Clark, L. J., Yu, J., Michalak, E. M., Happo, L., Cragg, M. S. & Inman, G. J. (2013). Transforming Growth Factor-beta Directly Induces p53-up-regulated Modulator of Apoptosis (PUMA) during the Rapid Induction of Apoptosis in Myc-driven B-cell Lymphomas. JOURNAL OF BIOLOGICAL CHEMISTRY, 288 (7), pp.5198-5209. https://doi.org/10.1074/jbc.M112.410274.; http://hdl.handle.net/11343/265254
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