Study On AGO2 Tyrosine Phosphorylation By C-Src Kinase

SRC,one classic proto-oncogene,encodes c-Src protein with tyrosine kinase activity.Numerous studies have reported that c-Src is highly expressed with high kinase activity in a variety of human tumors,and involved in multiple processes of cancer development,including cell proliferation,differentiation,angiogenesis and cancer survival rate.As a core component of the miRISC complex,AGO2 is involved in small RNAmediated gene silencing and regulation of partial miRNA maturation.AGO2 can undergo a variety of post-translational modifications,and the study of tyrosine phosphorylation modification is in its beginnings and has potential clinical implications in the treatment of tumors.We identify AGO2 protein is a new substrate for the c-Src kinase in our study.We first demonstrated the interaction between c-Src and AGO2 in 293 T cell and prokaryotic expression system,and that c-Src can phosphate AGO2 directly.Therefore,we searched for the phosphorylation sites of AGO2 and proved that tyrosine at positions393,529 and 749 were all the phosphorylation sites.Next,we explored the effects of pY-AGO2 on the maturation of miRNA and its role in tumorigenesis.It has been reported that phosphorylation of AGO2 at Tyr393 reduces its binding to DICER,thereby inhibiting miRNA maturation.We confirmed this view and found that the other two sites did not work through this mechanism.Our results also revealed that pY-AGO2 has an obvious tumor-promoting effect,but not the site-mutated stable cell lines,in addition to anti-tumor effect by treatment with c-Src inhibitor.Our results provide a new target and treatment idea for c-Src involved in tumorigenesis.