Visualisation, by immunocytochemistry, of p53 at the plasma membrane of both nontransformed and SV40-transformed cells.

The cellular protein p53 normally functions in the control of cell proliferation; but, when expressed abnormally p53 also contributes towards the process of cell transformation. The functioning of p53 is thought to involve interaction with specific cellular targets and, in SV40- and other transformed cells, p53 is located in the nucleus: thus p53 may function via interacting with specific nuclear components. In addition, there is indirect evidence that in SV40-transformed cells p53 is also associated with the plasma membrane; however, this is not evident in cells stained by immunofluorescence. We have sought to obtain direct evidence for p53 at the plasma membrane by staining with a very sensitive immunocytochemical procedure. We have compared SV40-transformed BALB 3T3 cells with BALB 3T3, NIH 3T3, and NIH 3T3 transfected with v-mos provirus. The last cell line is tumorogenic. We found direct evidence for p53 at the plasma membrane for each cell line. In nontransformed and SV40-transformed cells the association of p53 with the plasma membrane was restricted to the period of mitosis. These results indicate that association of p53 with the plasma membrane is a normal, rather than a transformation-related phenomenon, and is temporally linked to the period of mitosis.