CYLD is a 956 aa, cytoplasmic, deubiquitinating enzyme belonging to the ubiquitin carboxy-terminal hydrolases (UCH) family of proteins with three cytoskeletal-associated protein-glycine-conserved (CAP-GLY) domains, a proline rich region, a SH3 binding domain and a sequence homology to catalytic domain of UCH. CYLD is identified as a tumor suppressor protein affecting the JNK signaling pathway. CYLD is a negative regulator of TRAF2 and NF-kappa-B signaling pathway and is also known to have receptor-dependent role in regulating the I-kappa-B kinase pathway. It also has a deubiquitinating activity that is directed towards non-Lys-48-linked polyubiquitin chains and TRAP1 is a novel substrate for deubiquitination. Mutated CYLD is known to be associated with cylindromatosis, multiple familial trichoepithelioma, and Brooke-Spiegler syndrome.