The DnaJ family comprises a group of chaperone proteins that contain a J domain and have diverse cellular localization and functions. DnaJ proteins play a critical role in the HSP 70 chaperone machine by interacting with HSP 70 to stimulate ATP hydrolysis and are also important mediators of proteolysis and protein degradation. DnaJC9 (DnaJ (Hsp40) homolog, subfamily C, member 9), also designated HDJC9, JDD1 or DnaJ protein SB73, is a 260 amino acid protein found at moderate levels in most tissues with highest expression in the germinal zone of the central nervous system, testis, ovary, renal cortex and fetal liver. A member of the DnaJ family, DnaJC9 contains one N-terminal J domain but lacks the typical G/F and zinc finger regions that are typical of DnaJ family members. DnaJC9 localiizes to nuclei under normal conditions but may be transported to cytoplasm and plasma membrane when exposed to heat shock.