Analysis of the P53N a Novel Protein Encoded on Chromosome 22q12.1-12.3 in Glioblastomas and Ependymomas Specimens

The P 53N gene maps precisely to human chromosome sub-band 22q12.1-12.3, a region where loss of heterozygosity has been reported in 30% of astrocytic tumors and associated with progression to anaplasia. Moreover, a putative tumor suppressor gene has been indicated on 22q11 region involved in pathogenesis of ependymal tumors. Our objectives to examine the expression level of novel membrane-associated protein (termed P 53N ) encoded by a novel human gene on chromosome 22q12.1-12.3 in glioblastomas and ependymomas. Serial analysis of gene expression (SAGE) and immunofluorescence analysis of the P 53N in the brain tumor tissues were performed. Our analysis revealed that there was high expression of the P 53N mRNA in brain ependymoma and brain well-differentiated astrocytoma libraries. The P 53N protein . P 53N protein contains a high mobility group (HMG) domain at amino acid positions 301 to 360 expressed highly in glioblastoma and ependymoma specimens. Anti-P 53N carboxyl-terminal peptide antibody localized the P 53N protein to the cytoplasmic membranes of protoplasmic astrocytes in the glioblastoma and ependymoma specimens. These results are in good agreement with the SAGE analysis and the predicted transmembrane topology for the P 53N protein and support a possible transmembrane model in which the P 53N contains a predicted transmembrane region with its amino terminus localized to the inside of the cytoplasmic membrane.