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Updated: Jul 29, 2026
Inducible and Reversible Dominant-negative (DN) Protein Inhibition
Published on: January 7, 2019
Transcription repressor activity of spleen tyrosine kinase mediates breast tumor suppression
Lei Wang1, Eswaran Devarajan, Jin He
1Department of Molecular Pathology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA.
Abstract:
Spleen tyrosine kinase (SYK) is a candidate tumor suppressor gene in breast. Loss of SYK expression in breast tumors as a result of DNA hypermethylation promotes tumor cell proliferation and invasion and predicts shorter survival of breast cancer patients. We previously reported that, in addition to its well-known cytoplasmic localization, the full-length Syk is also present in the nucleus and that Syk nuclear translocation is a rate-limiting step to determine Syk tumor suppressor function. Here, we show that the full-length form of Syk acts as a transcription repressor in the cell nucleus. Ectopic expression of Syk down-regulates the transcription of FRA1 and cyclin D1 oncogenes. This transcription-repressing activity of Syk is associated with its binding to members of the histone deacetylase family. Syk interacts with transcription factor Sp1 at the Sp1 DNA-binding site in the FRA1 promoter to repress Sp1-activated FRA1 transcription. Thus, breast tumorigenesis and progression resulting from the loss of SYK are underscored by the derepression of Sp1-mediated oncogene transcription.
Insights
Spleen tyrosine kinase (SYK) loss in breast cancer allows oncogenes to promote tumor growth. Restoring SYK function suppresses these oncogenes, highlighting its tumor suppressor role.
Area of Science:
- Oncology
- Molecular Biology
- Gene Regulation
Background:
- Spleen tyrosine kinase (SYK) acts as a tumor suppressor in breast cancer.
- Loss of SYK expression, due to DNA hypermethylation, correlates with increased tumor proliferation, invasion, and reduced patient survival.
- SYK's nuclear translocation is critical for its tumor suppressor function.
Purpose of the Study:
- To investigate the molecular mechanisms underlying SYK's tumor suppressor activity in the nucleus.
- To determine how SYK regulates gene transcription and its role in breast cancer progression.
Main Methods:
- Studied the nuclear localization and function of full-length SYK.
- Analyzed the effect of SYK ectopic expression on oncogene transcription (FRA1, cyclin D1).
- Investigated SYK's interaction with histone deacetylases and transcription factor Sp1.
Main Results:
- Full-length SYK functions as a nuclear transcription repressor.
- Ectopic SYK expression down-regulates FRA1 and cyclin D1 oncogene transcription.
- SYK binds to histone deacetylases and represses Sp1-mediated transcription of FRA1 by interacting with Sp1 at the FRA1 promoter.
Conclusions:
- Loss of SYK in breast cancer leads to derepression of Sp1-mediated oncogene transcription, driving tumorigenesis and progression.
- SYK's nuclear function as a transcription repressor is a key mechanism of its tumor suppressor activity.
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