A Letamendia1, E Labbé, L Attisano. 1. Department of Anatomy and Cell Biology, University of Toronto, Ontario, Canada.
Abstract
BACKGROUND: Several studies have shown that cooperation between transforming growth factor beta (TGF-beta) and Wnt/wingless signaling pathways plays a role in controlling certain developmental events. These factors elicit their biological effects through distinct pathways in which TGF-beta and Wnt signaling induce activation of the transcriptional regulators Smads and lymphoid enhancer binding factor/T-cell-specific factor (LEF/TCF), respectively. To understand the mechanism for cooperativity between these pathways, we have investigated the molecular mechanism for this synergistic effect. METHODS: Transcriptional assays were conducted by transient transfection of HepG2 cells with use of luciferase reporter constructs. Protein/protein interaction studies were conducted in vitro with the use of glutathione-S-transferase pull-down assays and in intact cells by immunoprecipitation and immunoblotting. RESULTS: We show that Smads physically interact with LEF1/TCF transcription factors and that specific DNA binding sites in the Xenopus twin promoter are required for synergistic activation by TGF-beta and Wnt pathways. In addition, we demonstrate that TGF-beta-dependent activation of LEF1/TCF target genes can occur independently of beta-catenin, an essential component of the Wnt signaling pathway. CONCLUSIONS: TGF-beta and Wnt signaling pathways can independently or cooperatively regulate LEF1/TCF target genes. This suggests that the cooperation between these pathways may be important for the specification of cell fates during development.
BACKGROUND: Several studies have shown that cooperation between transforming growth factor beta (TGF-beta) and Wnt/wingless signaling pathways plays a role in controlling certain developmental events. These factors elicit their biological effects through distinct pathways in which TGF-beta and Wnt signaling induce activation of the transcriptional regulators Smads and lymphoid enhancer binding factor/T-cell-specific factor (LEF/TCF), respectively. To understand the mechanism for cooperativity between these pathways, we have investigated the molecular mechanism for this synergistic effect. METHODS: Transcriptional assays were conducted by transient transfection of HepG2 cells with use of luciferase reporter constructs. Protein/protein interaction studies were conducted in vitro with the use of glutathione-S-transferase pull-down assays and in intact cells by immunoprecipitation and immunoblotting. RESULTS: We show that Smads physically interact with LEF1/TCF transcription factors and that specific DNA binding sites in the Xenopus twin promoter are required for synergistic activation by TGF-beta and Wnt pathways. In addition, we demonstrate that TGF-beta-dependent activation of LEF1/TCF target genes can occur independently of beta-catenin, an essential component of the Wnt signaling pathway. CONCLUSIONS:TGF-beta and Wnt signaling pathways can independently or cooperatively regulate LEF1/TCF target genes. This suggests that the cooperation between these pathways may be important for the specification of cell fates during development.
Authors: Rongrong Zhang; Babatunde O Oyajobi; Stephen E Harris; Di Chen; Christopher Tsao; Hong-Wen Deng; Ming Zhao Journal: Bone Date: 2012-09-29 Impact factor: 4.398
Authors: András Masszi; Lingzhi Fan; László Rosivall; Christopher A McCulloch; Ori D Rotstein; István Mucsi; András Kapus Journal: Am J Pathol Date: 2004-12 Impact factor: 4.307
Authors: Xiaohong Li; Yongqing Wang; Ali-Reza Sharif-Afshar; Consolate Uwamariya; Andrew Yi; Kenichiro Ishii; Simon W Hayward; Robert J Matusik; Neil A Bhowmick Journal: Differentiation Date: 2008-10-25 Impact factor: 3.880