PIASy Represses The Transcription Activity Of ISGs

Background Interferon is a kind of glycoprotein that responses to the stimulation of virus and other organisms. Among them, type I interferon can activate intracellular JAK-STAT pathway and initiate the transcription of many ISGs, such as MX gene and IFITgene. But when the excessive activation of ISGs may lead to excessive body immunity, and even lead to many autoimmune diseases. PIAS protein is a kind of protein which can inhibit the activation of STATs transcription activity, thus it is involved in the negative regulation of ISGs. In addition, studies have found that PIASy can also reduced histone acetylation modification of promoter region through combination of HDAC1 and HDAC2, thereby inhibiting the transcription activity of Smad gene and AR gene. Therefore, this paper tries to find the molecular mechanism that PIASy may interact with histone modifying enzymes, and represses the transcription activity of ISGs. Methods Using Co-IP technology and mass spectrometry to find the histone modifying enzyme that PIASy interacts, and using RT-PCR and Ch-IP to detect the effect of PIASy on ISGS gene transcription and histone modification of promoter region; Using molecular cloning method to construct different domains of PIASy and RBP2 recombinant plasmid, and detect domains of combination by Co-IP;Construction of the stable expression cells of different domains of PIASy. Using RT-PCR and Ch-IP to detect the the effect of PIASy domains on ISGS gene transcription and histone modification of promoter region. Results PIASy can interact with RBP2, and in PIASy+/+ MEF cells, the MX1 and IFIT1 transcriptional activity and histone H3K4me3 levels were significantly lower than that in PIASy-/- cells; 1-218 AA of PIASy can combine with JmjC domain of RBP2; Consist with this, in PIASy-/- cells that stably expresses PIASy(1-218AA), the MX1 and IFIT1 transcriptional activity and histone H3K4me3 levels were significantly lower than that in PIASy-/- cells, thereby their transcription levels decreased. Conclusions The results show that PIASy can be recruited RBP2 protein to down-regulate ISGs(MX1, IFIT1) histone H3K4me3 level in promoter region, thereby inhibiting the transcription activity of ISGs.