NCKIPSD is localized exclusively in the cell nucleus. It plays a role in signal transduction, and may function in the maintenance of sarcomeres and in the assembly of myofibrils into sarcomeres. NCKIPSD also plays an important role in stress fiber formation. NCKIPSD gene is involved in therapy-related leukemia by a chromosomal translocation t(3;11)(p21;q23) that involves this gene and the myeloid/lymphoid leukemia gene. Alternative splicing occurs in this locus and two transcript variants encoding distinct isoforms have been identified. NCKIPSD is a SH3 domain protein. Fas ligand is a cytotoxic effector molecule of T and NK cells which is characterized by an intracellular N-terminal polyproline region that serves as a docking site for SH3 and WW domain proteins. Several previously described Fas ligand-interacting SH3 domain proteins turned out to be crucial for the regulation of storage, expression and function of the death factor. Recent observations, however, indicate that Fas ligand is also subject to posttranslational modifications including shedding and intramembrane proteolysis.