Abstract

In normal human cells, a protein with a molecular weight of about 53,000 (p53) is present at a low level, detectable only by sensitive assays. When the cells are infected with some DNA tumour viruses or transformed by the same viruses, the amount of this protein increases dramatically, and much of it is found in a physical association with the virus‐coded protein that causes the transformation. The increase in amount and, incidentally, stability of p53 is not peculiar to virus‐transformed cells, but also occurs in cells transformed by chemicals or radiation where there is no sign of any virus being involved (reviewed by Crawford).1 Cells in culture are not the same as cells in a patient, but these observations do raise questions about the possible involvement of p53 in human tumours.