The p73 protein is a member of the p53 family, and this protein is known to be essential for the maintenance of genomic stability, DNA repair, and apoptosis regulation. Transcription from two promoters leads to two main N-terminal isoforms: the TAp73 isoform is reported to have tumor suppressor function, whereas the ΔNp73 isoform likely has oncogenic potential. The present study is focused on the investigation of a possible role of both these p73 N-terminal isoforms in the process of centrosome amplification. HGG-02 and GM7 glioblastoma cell lines and the Daoy medulloblastoma cell line were used in this study. The cells were analyzed using indirect immunofluorescence to determine TAp73 and ΔNp73 expression patterns and possible co-localization with the BubR1 protein, as well as the number of centrosomes. A transiently transfected GM7 cell line was used to verify the results concerning the N-terminal isoforms in relation to centrosome amplification. We found that increased immunoreactivity for the ΔNp73 isoform is associated with the occurrence of an abnormal number of centrosomes in particular cells. Using the transiently transfected GM7 cell line, we confirmed that centrosome amplification is present in cells with overexpression of the ΔNp73 isoform. In contrast, the immunoreactivity for the TAp73 isoform was weak or medium in most of the cells with an aberrant number of centrosomes. To determine the putative counterpart of the p73 N-terminal isoforms among spindle assembly checkpoint (SAC) proteins, we also evaluated possible interactions between the N-terminal isoforms and BubR1 protein, but no co-localization of these proteins was observed.

• Keywords
• BubR1, Centrosome amplification, Glioblastoma multiforme, Medulloblastoma, TAp73, ΔNp73,
• MeSH
• Gene Amplification * MeSH
• Centrosome physiology   MeSH
• Chromosome Aberrations * MeSH
• DNA-Binding Proteins genetics   MeSH
• Fluorescent Antibody Technique, Indirect MeSH
• Nuclear Proteins genetics   MeSH
• Humans MeSH
• Tumor Cells, Cultured MeSH
• Tumor Suppressor Proteins genetics   MeSH
• Brain Neoplasms genetics   pathology   MeSH
• DNA Repair MeSH
• Promoter Regions, Genetic MeSH
• Protein Isoforms MeSH
• Tumor Protein p73 MeSH
• Protein Serine-Threonine Kinases genetics   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• BUB1 protein, human MeSH Browser
• delta Np73 protein, human MeSH Browser
• DNA-Binding Proteins MeSH
• Nuclear Proteins MeSH
• Tumor Suppressor Proteins MeSH
• Protein Isoforms MeSH
• Tumor Protein p73 MeSH
• Protein Serine-Threonine Kinases MeSH
• TP73 protein, human MeSH Browser

The protein homologous to the tumor suppressor p53, p73, has essential roles in development and tumorigenesis. This protein exists in a wide range of isoforms with different, even antagonistic, functions. However, there are virtually no detailed morphological studies analyzing the endogenous expression of p73 isoforms at the cellular level in cancer cells. In this study, we investigated the expression and subcellular distribution of two N-terminal isoforms, TAp73 and ΔNp73, in medulloblastoma cells using immunofluorescence microscopy. Both proteins were observed in all cell lines examined, but differences were noted in their intracellular localization between the reference Daoy cell line and four newly established medulloblastoma cell lines (MBL-03, MBL-06, MBL-07 and MBL-10). In the new cell lines, TAp73 and ΔNp73 were located predominantly in cell nuclei. However, there was heterogeneity in TAp73 distribution in the cells of all MBL cell lines, with the protein located in the nucleus and also in a limited non-random area in the cytoplasm. In a small percentage of cells, we detected cytoplasmic localization of TAp73 only, i.e., nuclear exclusion was observed. Our results provide a basis for future studies on the causes and function of distinct intracellular localization of p73 protein isoforms with respect to different protein-protein interactions in medulloblastoma cells.

• MeSH
• Cell Nucleus metabolism   MeSH
• Child MeSH
• DNA-Binding Proteins chemistry   metabolism   MeSH
• Intracellular Space metabolism   MeSH
• Nuclear Proteins chemistry   metabolism   MeSH
• Humans MeSH
• Medulloblastoma metabolism   pathology   MeSH
• Cell Line, Tumor MeSH
• Tumor Suppressor Proteins chemistry   metabolism   MeSH
• Child, Preschool MeSH
• Protein Isoforms metabolism   MeSH
• Tumor Protein p73 MeSH
• Protein Transport MeSH
• Check Tag
• Child MeSH
• Humans MeSH
• Male MeSH
• Child, Preschool MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• delta Np73 protein, human MeSH Browser
• DNA-Binding Proteins MeSH
• Nuclear Proteins MeSH
• Tumor Suppressor Proteins MeSH
• Protein Isoforms MeSH
• Tumor Protein p73 MeSH
• TP73 protein, human MeSH Browser