title: Transcription repressor activity of spleen tyrosine kinase mediates breast tumor suppression.
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.
authors.affiliation: Department of Molecular Pathology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Eswaran
authors.initials: E
authors.lastname: Devarajan
authors.forename: Jin
authors.initials: J
authors.lastname: He
authors.forename: Sekhar P
authors.initials: SP
authors.lastname: Reddy
authors.forename: Jia Le
authors.initials: JL
authors.lastname: Dai
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D004792:Enzyme Precursors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000072377:Syk Kinase; D015533:Transcriptional Activation
chemical_list: D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D012097:Repressor Proteins; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; D006655:Histone Deacetylases