Identification of tudor repeat associator with PCTAIRE 2 (Trap) - A novel protein that interacts with the N-terminal domain of PCTAIRE 2 in rat brain

PCTAIRE 2 is a Cdc2-related kinase that is predominantly expressed in the t erminally differentiated neuron. To elucidate the function of PCTAIRE 2, pr oteins that associate with PCTAIRE 2 were screened by the yeast two-hybrid system. A positive clone was found to encode a novel protein that could bin d to PCTAIRE 2 in vitro as well as in vivo, and was designated as Trap (tud or repeat associator with PCTAIRE 2). The overall structure of Trap shows n o significant homology to any proteins, but contains five repeated domains (the tudor-like domain), conserved in Drosophila tudor protein. Trap associ ates with the N-terminal domain of PCTAIRE 2 through its C-terminal domain, which contains two tudor-like domains. PCTAIRE 1, but not PCTAIRE 3, can a lso associate with Trap. Trap is predominantly expressed in brain and testi s, and gradually increases during brain development throughout life, consis tent with the expression pattern of PCTAIRE 2. Immunoreactivities for PCTAI RE 2 and Trap were colocalized to the mitochondria in COS 7 cells. Immunohi stochemical analyses showed that PCTAIRE 2 and Trap were distributed in the same cell layer of the cerebral cortex and cerebellum. These findings sugg est that Trap is a physiological partner of PCTAIRE 2 in terminally differe ntiated neurons.