Under CA34610 we previously identified the TGF-beta and BMP receptors, resolved the mechanism of receptor activation, identified Smad proteins as receptor substrates and transcriptional regulators, and delineated the basic mechanics of Smad nuclear accumulation and target gene selection. Having thus defined a contiguous pathway from TGF-beta and BMP ligands to target genes, the current round of R37 MERIT funding is focusing on the integration of this pathway in the signalling networks of normal cells, its disruption in cancer and its corruption in metastasis. Over the first four years of the current funding cycle, we have made progress towards each of our specific aims.
Under Specific Aim I, we discovered that CDK8/9 kinases phosphorylate Smad proteins in the nucleus to drive Smad transcriptional action and turnover in BMP and TGF-beta signaling. We also found that mitogen and stress-activated MAPKs phosphorylate this region in the cytoplasm to counterbalance BMP and TGF-betg signaling. We identified CTD phosphatases as the mediators of dephosphorylation of the linker region, providing a more complete picture of these core events in the TGF-beta and BMP pathways.
Under Specific Aim II, we identified important Smad target genes and partner proteins In normal and malignant cells, including cytolytic genes as targets of TGF-beta during tumor evasion of immune surveillance by cytotoxic T-lymphocytes. In metastatic breast cancer cells we demonstrated that the Smad pathway triggers induction of Angiopoietin-like 4 expression for lung Infiltration and of interleukin-11 and connective tissue growth factor (CTGF) for osteolytic bone metastasis. We also defined the role of the BRG1 SWI/SNF chromatin-remodeling complex In the genome-wide response of cells to TGF-beta.
Under Specific Aim III, we defined the role of FOXO and C/EBPb transcription factors as Smad co-regulators of cytostatic genes responses (p21CIP1, p15INK4B and MYC gene responses). We identified a malfunction of C/EBPb as the basis for the evasion of these tumor-suppressive responses in metastatic breast carcinoma cells.
Under Specific Aim I V we identified TIF1g as a novel partner of TGF-beta activated Smad2/3 in the control of progenitor cell differentiation. Building on this progress, we will investigate the connectivity and regulation of TGF-beta and BMP pathways with other major regulators of cell behavior in the normal and the malignant state.

National Institute of Health (NIH)
Method to Extend Research in Time (MERIT) Award (R37)
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Salnikow, Konstantin
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Oskarsson, Thordur; Batlle, Eduard; Massagué, Joan (2014) Metastatic stem cells: sources, niches, and vital pathways. Cell Stem Cell 14:306-21
Hynes, Nancy E; Ingham, Philip W; Lim, Wendell A et al. (2013) Signalling change: signal transduction through the decades. Nat Rev Mol Cell Biol 14:393-8
Vanharanta, Sakari; Massagué, Joan (2013) Origins of metastatic traits. Cancer Cell 24:410-21
Xi, Qiaoran; Wang, Zhanxin; Zaromytidou, Alexia-Ileana et al. (2011) A poised chromatin platform for TGF-? access to master regulators. Cell 147:1511-24
Aragón, Eric; Goerner, Nina; Zaromytidou, Alexia-Ileana et al. (2011) A Smad action turnover switch operated by WW domain readers of a phosphoserine code. Genes Dev 25:1275-88
Gao, Sheng; Alarcon, Claudio; Sapkota, Gopal et al. (2009) Ubiquitin ligase Nedd4L targets activated Smad2/3 to limit TGF-beta signaling. Mol Cell 36:457-68
Alarcon, Claudio; Zaromytidou, Alexia-Ileana; Xi, Qiaoran et al. (2009) Nuclear CDKs drive Smad transcriptional activation and turnover in BMP and TGF-beta pathways. Cell 139:757-69
Xi, Qiaoran; He, Wei; Zhang, Xiang H-F et al. (2008) Genome-wide impact of the BRG1 SWI/SNF chromatin remodeler on the transforming growth factor beta transcriptional program. J Biol Chem 283:1146-55
Padua, David; Zhang, Xiang H-F; Wang, Qiongqing et al. (2008) TGFbeta primes breast tumors for lung metastasis seeding through angiopoietin-like 4. Cell 133:66-77
Sapkota, Gopal; Alarcon, Claudio; Spagnoli, Francesca M et al. (2007) Balancing BMP signaling through integrated inputs into the Smad1 linker. Mol Cell 25:441-54

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