Suppressor of Cytokine Signaling (SOCS/SSI) Family Genes encode cytokine-specific-inducible negative feedback regulators that function downstream of cytokine receptors to attenuate signal transduction. Suppressor of Cytokine Signaling Proteins contain SH2 and SOCS BOX domains and are implicated, through SOCS box binding, in ubiquitin-dependent protein degradation. SOCS proteins interact with multiple tyrosine kinase activated signaling proteins and inhibit cytokine signal transduction by binding to tyrosine kinase receptors. SOCS proteins regulate cell growth and survival, placental development, hematopoiesis, and T-cell allergic responses. (NCI) [ ]