The Molecular Mechanism On The Negative Regulation Of Igε Gene Transcription In IL-4/STAT6 Pathway

Objective:STAT6 is one member of the STATs family of signal transducers and activators of transduction. It can be activated by IL-4. IL-4 binds to its receptor and activate JAK/STAT6 pathway. The activation signal passes along protein-protein interaction cascades and finally activates the transcription and expression of target gene. Over-activation of IL-4/JAK/STAT6 signal transduction pathway participate the pathogenesis and progression of several diseases, which involve hypersensitivity and tumor. Previous studies showed that STAT6-TAD can bind to a series of transcription coactivators including p100, CBP and NCoA-1 to increase its transcriptional activity and gene expression. But the mechanism of gene transcription mediated by STAT6 has not been identified. PSF is a gene transcription inhibitory factor we identified by mass spectrometry analysis of the STAT6-TAD interacting proteins after IL-4 stimulation. The purpose of this study is to reveal the mechanism of its regulation.Methods:The study is divided into two parts:the first part is to study the functional domain of STAT6 which mediates the interaction between PSF and STAT6 by CO-Immunoprecipitation. In order to identify the functional domain of PSF which mediates the interaction between PSF and STAT6, we construct eukaryotic green fluorescent protein(GFP) expressing recombinant plasmids, pEGFP-C2-PSF(Ⅰ～Ⅴ), which contain human PSF fragments. The second part is to observe the change of acetylation of histone H3 affected by over-expressed PSF when the influence of PSF upon the interaction between STAT6 and Igεpromoter is ascertained by the Chromatin Immunoprecipitation Assay.Result:①PSF interacted with the STAT6 mediated by STAT6-TAD in vivo. The expression vector pEGFP-C2-PSF(Ⅰ～Ⅴ) was successfully constructed.②After IL-4 stimulation, PSF can inhibits the binding of STAT6 to Igεpromoter.③The over-expressed PSF contributed to the decreased level of acetylation of histone H3. Conclusion:①PSF protein is capable of interacting with the STAT6 protein directly via STAT6-TAD.②PSF can inhibit the activity of Igεtranscription by deacetylation of histone H3.