ZNF198 is a ubiquitously expressed nuclear protein whose physiological role is largely unknown. It consists of 5 N-terminal zinc finger motifs responsible for protein-protein interactions, a central proline-rich domain and C-terminal nuclear localization signal (NLS) and an acidic domain. Reciprocal chromosomal translocation involving ZNF198 and FGFR1 results in the formation of ZNF198/FGFR1 fusion kinase protein. This fusion protein is a ligand-dependent, constitutively active cytoplasmic tyrosine kinase and regulates several STAT transcription factors including STAT 1, 3 and 5. This fusion protein is an oncogenic protein and is associated with an atypical myeloproliferative disease, peripheral blood eosinophilia and T-cell leukemia/lymphoma.