title: Impaired p53 expression, function, and nuclear localization in calreticulin-deficient cells.
abstract: The tumor suppressor protein, p53 is a transcription factor that not only activates expression of genes containing the p53 binding site but also can repress the expression of some genes lacking this binding site. Previous studies have shown that overexpression of wild-type p53 leads to apoptosis and cell cycle arrest. DNA damage, such as that caused by UV irradiation, results in p53 stabilization and nuclear localization that subsequently induces apoptosis. Recently, the level of calreticulin (CRT) has been correlated with the rate of apoptosis. Therefore, the aim of this study was to investigate the role of CRT in the regulation of apoptosis via modulating p53 function and expression. Here we show a significant decrease in both basal and DNA damage induced p53 functions in the CRT-deficient cells (crt-/-). This study is the first to demonstrate that CRT function is required for the stability and localization of the p53 protein. By using immuonocytochemical techniques, we showed that observed changes in p53 in the crt-/- cells are due to the nuclear accumulation of Mdm2 (murine double minute gene). These results, lead us to conclude that CRT regulates p53 function by affecting its rate of degradation and nuclear localization.
authors.affiliation: Division of Stroke and Vascular Disease, St. Boniface General Hospital Research Centre, University of Manitoba, Winnipeg, Canada R2H 2A6. nmasaeli@sbrc.ca
authors.forename: Nasrin
authors.initials: N
authors.lastname: Mesaeli
authors.forename: Clark
authors.initials: C
authors.lastname: Phillipson
mesh_terms: D000818:Animals; D017209:Apoptosis; D001665:Binding Sites; D015153:Blotting, Western; D037282:Calreticulin / Q000235:genetics / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism*; D004249:DNA Damage; D005347:Fibroblasts / Q000378:metabolism; D017930:Genes, Reporter; D015151:Immunoblotting; D007150:Immunohistochemistry; D051379:Mice; D008957:Models, Genetic; D009687:Nuclear Proteins / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis* / Q000378:metabolism / Q000502:physiology*; D014466:Ultraviolet Rays
chemical_list: D037282:Calreticulin; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2