SOCS3 is a member of the STAT-induced STAT inhibitor (SSI), also known as suppressor of cytokine signaling (SOCS), family. SSI family members are cytokine-inducible negative regulators of cytokine signaling. The expression of SOCS3 is induced by various cytokines, including IL6, IL10, and interferon (IFN)-gamma. This protein can bind to JAK2 kinase, and inhibit the activity of JAK2 kinase. Studies of the mouse counterpart of this gene suggested the roles of this gene in the negative regulation of fetal liver hematopoiesis, and placental development. Recombinant human SOCS3 protein, fused to His-tag at N-terminus, was expressed in E.coli.