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FAST-2 is a mammalian winged-helix protein which mediates transforming growth factor beta signals
1Cell Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, USA.
Abstract:
The mechanisms by which transforming growth factor beta (TGF-beta) and related ligands regulate transcription remain poorly understood. The winged-helix (WH) transcription factor fork head activin signal transducer 1 (FAST-1) was identified as a mediator of activin signaling in Xenopus embryos (X. Chen, M. J. Rubock, and M. Whitman, Nature 383:691-696, 1996). We have cloned a novel WH gene from the mouse which shares many properties with FAST-1. We find that this gene, which we call FAST-2, is able to mediate transcriptional activation by TGF-beta. FAST-2 also interacts directly with Smad2, a cytoplasmic protein which is translocated to the nucleus in response to TGF-beta, and forms a multimeric complex with Smad2 and Smad4 on the activin response element, a high-affinity binding site for FAST-1. Analysis of the sequences of FAST-1 and FAST-2 reveals substantial protein sequence divergence compared to known vertebrate orthologs in the WH family. This suggests that FAST-2 represents a new WH gene related to FAST-1, which functions to mediate TGF-beta signals in mammals. We have also examined the structure of the FAST-2 gene and find that it overlaps with a kinesin motor protein gene. The genes are transcribed in opposite orientations, and their transcripts overlap in the 3' untranslated region.
Insights
Researchers identified FAST-2, a novel winged-helix gene in mice, that mediates transforming growth factor beta (TGF-beta) signaling by interacting with Smad2 and Smad4. This discovery sheds light on TGF-beta transcriptional regulation in mammals.
Area of Science:
- Molecular Biology
- Developmental Biology
- Genetics
Background:
- Transforming growth factor beta (TGF-beta) signaling pathways are crucial for cellular processes but their transcriptional regulation mechanisms are not fully understood.
- Fork head activin signal transducer 1 (FAST-1) is a winged-helix (WH) transcription factor known to mediate activin signaling in Xenopus embryos.
Purpose of the Study:
- To identify and characterize novel genes involved in TGF-beta signaling in mammals.
- To elucidate the role of a newly identified WH gene, FAST-2, in mediating TGF-beta transcriptional responses.
Main Methods:
- Cloning of a novel mouse WH gene, designated FAST-2.
- Investigating FAST-2's ability to mediate transcriptional activation by TGF-beta.
- Analyzing protein-protein interactions between FAST-2, Smad2, and Smad4.
- Examining the gene structure and organization of FAST-2 and its overlap with a kinesin gene.
Main Results:
- FAST-2 was identified as a mouse WH gene that mediates TGF-beta transcriptional activation.
- FAST-2 directly interacts with Smad2 and forms a multimeric complex with Smad2 and Smad4 on the activin response element.
- Sequence analysis revealed significant divergence from known WH family orthologs, suggesting FAST-2 is a distinct mammalian gene.
- The FAST-2 gene structure shows overlap with a kinesin motor protein gene, with opposite transcription orientations.
Conclusions:
- FAST-2 is a novel WH transcription factor that functions in mammalian TGF-beta signaling pathways.
- FAST-2 acts as a critical mediator, interacting with Smad proteins to regulate gene transcription in response to TGF-beta.
- The unique sequence and gene organization of FAST-2 highlight its specialized role in mammalian biology.