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A novel transcriptional factor with Ser/Thr kinase activity involved in the transforming growth factor (TGF)-beta
S Ohta1, M Takeuchi, M Deguchi
1Shionogi Research Laboratories, Shionogi & Co. Ltd, 5-12-4Sagisu, Fukushima-ku, Osaka, Osaka 553-0002, Japan.
Abstract:
Transforming growth factor-beta (TGF-beta) shows a variety of biological activities in various organs or cells. Recently some factors such as Smads (Sma and Mad proteins) and TGF-beta activating kinase 1 ('TAK1') have been characterized as signalling molecules downstream of TGF-beta. Several TGF-beta response elements have been identified such as cAMP response element, Smad binding element, and recognition sites for activating protein-1 and stimulating protein-1 in various gene promoters. We also reported a TGF-beta response element in the human C-type natriuretic peptide (CNP) gene promoter. In this paper, we report on a novel factor which regulates the TGF-beta response promoter. This factor, named TSF1 (TGF-beta stimulated factor 1), possessed DNA-binding ability and activated the TGF-beta responsive CNP promoter or vascular endothelial growth factor gene promoter which possesses a sequence element analogous to the TGF-beta responsive GC-rich element of the CNP promoter. TSF1 did not directly activate a Smads-dependent promoter from plasminogen activator inhibitor 1 gene, but it showed enhancement in co-operation with Smad3 and Smad4. Interestingly, this factor had the structural features of a Ser/Thr kinase and actually exhibited protein kinase activity. TSF1 mRNA as well as its protein level were stimulated by TGF-beta treatment. Thus, TSF1 is an unique factor with two biological functions, transcriptional regulation and protein phosphorylation, that may be involved in TGF-beta signals.
Insights
A novel factor, TGF-beta stimulated factor 1 (TSF1), regulates gene expression and possesses kinase activity, responding to TGF-beta signals. TSF1 enhances TGF-beta pathways by binding DNA and phosphorylating proteins.
Area of Science:
- Molecular Biology
- Cell Signaling
- Gene Regulation
Background:
- Transforming growth factor-beta (TGF-beta) is a key signaling molecule with diverse biological roles.
- Downstream signaling molecules like Smads and TGF-beta activating kinase 1 (TAK1) have been identified.
- TGF-beta response elements are found in various gene promoters, including the human C-type natriuretic peptide (CNP) gene.
Purpose of the Study:
- To identify and characterize novel factors regulating TGF-beta responsive promoters.
- To investigate the function and properties of a newly discovered factor, TSF1.
Main Methods:
- DNA-binding assays to assess TSF1's interaction with gene promoters.
- Reporter gene assays to measure TSF1's transcriptional activation.
- Analysis of TSF1's kinase activity and its interaction with Smad proteins.
- Quantitative analysis of TSF1 mRNA and protein levels following TGF-beta treatment.
Main Results:
- A novel factor, TSF1, was identified with DNA-binding ability.
- TSF1 activates TGF-beta responsive promoters, including the CNP and vascular endothelial growth factor (VEGF) gene promoters.
- TSF1 exhibits Ser/Thr kinase activity and enhances Smad3/Smad4-dependent transcription.
- TGF-beta treatment stimulates TSF1 mRNA and protein expression.
Conclusions:
- TSF1 is a unique bifunctional molecule involved in TGF-beta signaling, possessing both transcriptional regulatory and protein kinase activities.
- TSF1 plays a role in mediating TGF-beta-induced cellular responses.
- Further research into TSF1 could elucidate novel therapeutic targets for TGF-beta-related diseases.