TNK1 (Tyrosine kinase, non-receptor, 1) is a nonreceptor tyrosine kinase (NRPTK). These kinases, like members of the SRC (MIM 190090) and JAK (see MIM 147795) families,Mouse,ediate intracellular signaling downstream of receptor activation. Tnk1 is a ubiquitously e, Xenopus/Amphibian,pressed 47-kDa protein with autotyrosine kinase activity that is developmentally regulated during embryogenesis. Tnk1 is also upregulated following IL3 withdrawal from factor-dependent murine NSF/N1.H7 cells that undergo apoptosis, suggesting a role in growth inhibition. Data support a negative regulatory role for Tnk1 in regulating the Ras-Raf1-MAPK growth pathway by a mechanism that requires its autotyrosine kinase activity.