Stabilization of the p53 transformation-related protein in mouse fibrosarcoma cell lines: effects of protein sequence and intracellular environment.

Abstract

The transformation-related protein p53 is normally very labile. The stability of p53 is significantly increased in a number of fibrosarcoma cell lines derived from mouse tumors induced by treatment with physical or chemical agents. In many instances, p53 stabilization is correlated with the ability to form a stable complex with the heat shock protein cognate hsc7O. We describe a line in which p53 is very stable yet has no detectable interaction with hsc7O. The inability to form such a complex probably resides in the primary structure of the endogenous p53, since introduction of other p53 variants into those cells resulted in the appearance of a p53-hsc7O complex. The factors affecting p53 stability were investigated by stable transfection experiments. The results indicated that the primary structure of the p53 protein is a major determinant of its turnover rate; different p53 variants were degraded at distinct and characteristic rates in a number of transformed cell types. However, at least one p53 variant was degraded differently in nontransformed BALB/c-3T3 than in transformed fibrosarcoma cells, demonstrating that the specific cellular environment can also affect the stability of p53.

Loss of function and p53 protein stabilization

“…Complex formation with T antigen (and HSP70) does not directly stabilize p53 (Halevy et al, 1989). Moreover, E1A does not form a complex with p53 (Debbas and White, 1993).…”

Role of tumor suppressor genes in the development of adult T cell leukemia/lymphoma (ATLL)

“…206 The p53 gene is frequently mutated in a variety of tumors including hematologic malignancies. 132,133,207,208 Unlike functional p53, which is rapidly degraded within 5 to 20 min after its synthesis, 209 mutant versions of the proteins have a half-life of 4 to 8 h 210 and accumulate in the cells, thus becoming immunohistochemically detectable.…”

Characterization of sequence elements involved in p53 stability regulation reveals cell type dependence for p53 degradation

“…Previous studies have suggested that the turnover rate of mutant p53 is at least in part dependent on the cellular context indicated by the fact that tumor mutants have a signi®cantly shortened half-life in wt p53 containing cells than in cells devoid of wt p53 (Halevy et al, 1989;Midgley and Lane, 1997). This hypothesis is strongly supported by the present study (Figure 4).…”

“…Studies examining the expression of tumor derived mutant p53 proteins in wt p53 containing cells had suggested that degradation of p53 is dependent on the cellular environment (Halevy et al, 1989;Midgley and Lane, 1997). To test this hypothesis, the D62 ± 96 form of wt p53 was stably expressed in a number of cell lines which di er in their endogenous p53 status.…”

“…Since mutant p53 proteins often adopt a di erent conformation than wt p53 (Milner, 1994), this may indicate that a proper conformation is important for p53 to be recognized as a proteolytic substrate. However, studies examining the half-life of mutant p53s upon ectopic expression in cells containing wt p53 suggest that the turnover rate of p53 is in¯uenced by the cellular environment and may not, or only partially, be dependent on a wt p53-like conformation (Halevy et al, 1989;Midgley and Lane, 1997).…”