Oncoprotein p53 expression in normal, immortalized, and transformed mouse fibroblasts.
We have compared the rate of synthesis, half-life, and steady-state content of the oncoprotein p53 in logarithmically growing cultures of (a) primary embryo, (b) immortalized but untransformed, and (c) spontaneously transformed mouse fibroblasts. Steady-state p53 content derived from metabolic labeling and immunoprecipitation data revealed either no change or only a slight decrease (up to 1.5-fold depending on the antibody used) in transformed cells compared with immortal or primary cultures, p53 showed the same short half-life in all cell types. In contrast, immunocytochemical analysis of p53 content in intact cells demonstrated an increase in the proportion of cells with detectable nuclear p53 from approximately 4% in primary and immortal cultures to approximately 10% in fully transformed cells, together with a marked increase in the intensity of nuclear positivity. We suggest that transformation is associated with an increase in the cellular content of p53 in a subcellular pool which was not detectable in detergent for immunoprecipitation. In addition, immunocytochemical analysis demonstrated a marked heterogeneity in p53 content in all cell types which was not related to clonal variation, cell cycle phase, or growth state. These data challenge previous suggestion regarding the role of p53 in growth control.
Williams
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NW
Department of Pathology, University of Wales College of Medicine, Carddiff, United Kingdom.
Wynford-Thomas
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D
D000818:Animals; D002455:Cell Division; D002461:Cell Line, Transformed; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D015870:Gene Expression; D007150:Immunohistochemistry; D051379:Mice; D015513:Oncogene Proteins / Q000235:genetics*; D010750:Phosphoproteins / Q000235:genetics*; D016159:Tumor Suppressor Protein p53
D015513:Oncogene Proteins; D010750:Phosphoproteins; D016159:Tumor Suppressor Protein p53