The Function And Mechanism Of H3K4 Transmethylase SET1A Upregulate YAP

Hippo pathway is an evolutionarily conserved signaling cascade,regulates cell proliferation and apoptosis to control organ size and stem cell property,which is considered to correlate with development and progression of cancer.In response to adverse growing conditions,Mst1/2 associates with WW45 and activated by phosphorylation,then activates Lats1/2-Mob complex,which phosphorylates YAP/TAZ.The Lats-dependent phosphorylation of YAP/TAZ facilitates binding to 14-3-3,leading to their cytoplasmic retention,or be ubiquitinated by ?-Trcp E3 ligase,and functional inactivation.On the contrary,YAP/TAZ localizes in the nuclear and binds with TEAD1-4 to activate expression of target genes.Protein lysine methyltransferases been identified to have critical roles in the histone modifications,also they may methylated non-histone proteins,such as p53,RB1 and STAT3 etc,and played important roles in human tumorigenesis.Post-translational modifications of core Hippo pathway proteins,especially phosphorylation and ubiquitylation have been well studied.We are interested in the regulatory mechanism and physiological function of methylation of the Hippo pathway.To identify the methylases responsible for Hippo pathway,we performed a whole methylase-wide screen and totally 11 methylases were included,which led us to find that SET1A remarkedly upregulated YAP reporter,gene.Depletion of SET1A by siRNA dramatically decreased YAP target gene levels,ectopic expression of SET1A,but not the SET domain deficient mutant,resulted in YAP signaling elevation in a dose-dependent manner.Binding assays showed SET1A interacted with YAP independent of its SET activity.Deletion analysis demonstrated that the PPXY motif mediated the physical interaction with YAP.Additionally,we mapped the SET1A-binding region of YAP to the WW domain.Since SET1A is a methylase,we went on to examine the possibility that SET1A methylates YAP.Indeed,in vivo methylation assays showed that SET1A specifically and directly methylated YAP.To extend our findings,we performed immunofluorescence and found YAP was accumulated in the cytoplasm by downregulating SET1A.We found that LMB remarkedly inhibited the nuclear localization of YAP,LA mutants inhibited YAP protein export.We next performed over expression assay,found that SET1A inhibited the binding of YAP and CRM1.On the cell level,the MTT assay of H1299 cell line,deregulation of SET1A inhibited cell proliferation;and xenograft tumorigenesis also confirmed that like YAP,knockdown SET1A inhibited tumor formation.We then performed IHC staining in lung cancer chip,and found that SET1A and YAP were remarkedly positively stained and correlated.The patient survival analysis also found that YAP and SET1A level in patients correlated with their prognosis.In summary,we found SET1A methylates YAP,inhibites its nuclear export,promotes target transcription factor activity,through direct interacting with YAP,thus promoting cancer cell growth and tumorigenesis.