NAIF protein 1 belongs to the NAIF1 family. Apoptosis is a genetically determined cell suicidal pro gram that plays critical roles in many physiological and pathological processes. nuclear apoptosis-inducing factor 1 (NAIF1), overexpression of which induces apoptosis in cells. Human NAIF1 is located on chromosome 9q34.11 and encodes 327 amino acids with a homeodomain-like region and two nuclear localization signals at its N-terminal region. Northern blot analysis revealed wide expression of NAIF1 mRNA throughout human tissues.