The Negative Regulation Of Igε Gene Transcription In IL-4/STAT6 Pathway Via Histone Acetylation

Objective:Signal transduction is a mechanism that converts a stimulus to a cell into a specific cellular response, through which the cell makes modifications in either activity of enzymes or gene transcription. 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 laser scanning confocal microscopy and CO-Immunoprecipitation. The second part is to address the role of PSF/HDAC1 in IL-4/STAT6 induced gene expression.chromatin immunoprecipitation assays were performed to detect the acetylation of H3 at the Igs promoter region.And glycerol density gradient ultra centrifugation were performed to reveal how PSF participate in the complexes of HDACs to regulate IL-4/STAT6 transcriptional activity.Result:①IL-4 stimulation induced the co-location of STAT6 and PSF. And PSF interacted with the STAT6 mediated by STAT6-TAD in vivo. In addition,the IL-4 induced modification of both STAT6 and PSF is a prerequisite for the association of these two proteins.②After IL-4 stimulation, PSF recruits HDAC1 to STAT6 complex and overexpression of PSF reduce the H3 acetylation at the Igs promoter to regulate IL-4/STAT6 transcriptional activity.And the HDACs inhibitor trichostatina(TSA) treatment enhances the H3 acetylation at the Igεpromoter after IL-4 stimulation.Conclusion:①fter IL-4 stimulation,PSF protein is capable of interacting with the STAT6 protein directly via STAT6-TAD.②PSF recruits HDAC1 and reduces the H3 acetylation at the Igεpromoter to regulate IL-4/STAT6 transcriptional activity.