Multiple subcellular localizations of PCTAIRE-1 in brain

We developed a selective antibody to a synthetic peptide corresponding to a n N-terminal sequence of the PCTAIRE-1 protein. In rodent brain extracts it recognized only the protein doublet characteristic of PCTAIRE-1, and this signal is completely abolished by preincubation of the antibody with the im munopeptide. Immunolabeling experiments done with this PCTAIRE-1-specific a ntibody reveal that the protein is widely distributed in the rodent brain a s are the mRNAs visualized using an antisense riboprobe corresponding to th e entire PCTAIRE-1 open reading frame. Two types of PCTAIRE-1 protein local izations were observed: first a diffuse labeling of almost all brain region s, particularly intense in the molecular layer of the cerebellum and the mo ssy fiber region of the hippocampus, and second a spot-like localization in the nuclei of large neurons such as cerebellar Purkinje cells and pyramida l cells of the hippocampus. Colocalization with the B23 protein allows one to identify these compartments as nucleoli. Our results suggest a nucleolar function of PCTAIRE-1 in large neurons and a role in regions containing im portant granule cell projections.