Correlation of metabolic stability and altered quaternary structure of oncoprotein p53 with cell transformation

Kraiss, Stefan; Spiess, S; Reihsaus, Ellen; Montenarh, Mathias

doi:10.1016/0014-4827(91)90170-y

Cited by 56 publications

(32 citation statements)

References 32 publications

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“…14 In contrast, mutant p53 has a much longer half-life, and therefore, accumulates in the nucleus creating a stable target for immunohistochemical detection. 15,16 Although some studies have described immunohistochemical overexpression of wild-type p53, suggesting abnormal stability of non-mutant protein due to impaired degradation under cellular stress, strong and diffuse immunolabeling is generally regarded as indicative of a missense mutation of TP53. 1,7,17 It has been proposed, but not as well appreciated that complete lack of immunohistochemical expression may be a result of a nonsense mutation leading to formation of a truncated, nonimmunoreactive protein.…”

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confidence: 99%

Immunohistochemical staining patterns of p53 can serve as a surrogate marker for TP53 mutations in ovarian carcinoma: an immunohistochemical and nucleotide sequencing analysis

et al. 2011

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Immunohistochemical staining for p53 is used as a surrogate for mutational analysis in the diagnostic workup of carcinomas of multiple sites including ovarian cancers. Strong and diffuse immunoexpression of p53 is generally interpreted as likely indicating a TP53 gene mutation. The immunoprofile that correlates with wild-type TP53, however, is not as clear. In particular, the significance of completely negative immunostaining is controversial. The aim of this study was to clarify the relationship of the immunohistochemical expression of p53 with the mutational status of the TP53 gene in ovarian cancer. A total of 57 ovarian carcinomas (43 high-grade serous ovarian/peritoneal carcinomas, 2 malignant mesodermal mixed tumors (carcinosarcomas), 2 low-grade serous carcinomas, 4 clear cell carcinomas, 1 well-differentiated endometrioid carcinoma, and 5 carcinomas with mixed epithelial differentiation) were analyzed for TP53 mutations by nucleotide sequencing (exons 4-9), and subjected to immunohistochemical analysis of p53 expression. Thirty six tumors contained functional mutations and 13 had wild type TP53. Five tumors were found to harbor known TP53 polymorphism and changes in the intron region were detected in three. Tumors with wild-type TP53 displayed a wide range of immunolabeling patterns, with the most common pattern showing r10% of positive cells in 6 cases (46%). Mutant TP53 was associated with 60-100% positive cells in 23 cases (64% of cases). This pattern of staining was also seen in three cases with wildtype TP53. Tumors that were completely negative (0% cells staining) had a mutation of TP53 in 65% of cases and wild-type TP53 in 11%. Combining two immunohistochemical labeling patterns associated with TP53 mutations (0% and 60-100% positive cells), correctly identified a mutation in 94% of cases (Po0.001). Immunohistochemical analysis can be used as a robust method for inferring the presence of a TP53 mutation in ovarian carcinomas. In addition to a strong and diffuse pattern of p53 expression (in greater than 60% of cells), complete absence of p53 immunoexpression is commonly associated with a TP53 mutation. Accordingly, this latter pattern, unlike low-level expression (10-50% cells), should not be construed as indicative of wild-type TP53.

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Immunohistochemical staining patterns of p53 can serve as a surrogate marker for TP53 mutations in ovarian carcinoma: an immunohistochemical and nucleotide sequencing analysis

et al. 2011

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“…Early cell-based studies found that p53 forms high molecular weight aggregates in transformed cells and other cells (10)(11)(12).…”

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Kinetic mechanism of p53 oncogenic mutant aggregation and its inhibition

Wilcken

Wang

Boeckler

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

111

137

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Aggregation of destabilized mutants of the tumor suppressor p53 is a major route for its loss of activity. In order to assay drugs that inhibit aggregation of p53, we established the basic kinetics of aggregation of its core domain, using the mutant Y220C that has a mutation-induced, druggable cavity. Aggregation monitored by light scattering followed lag kinetics. Electron microscopy revealed the formation of small aggregates that subsequently grew to larger amorphous aggregates. The kinetics of aggregation produced surprising results: progress curves followed either by the binding of Thioflavin T or the fluorescence of the protein at 340 nm fitted well to simple two-step sequential first-order lag kinetics with rate constants k 1 and k 2 that were independent of protein concentration, and not to classical nucleation-growth. We suggest a mechanism of first-order formation of an aggregation competent state as being rate determining followed by rapid polymerization with the higher order kinetics. By measuring the inhibition kinetics of k 1 and k 2 , we resolved that the process with the higher rate constant followed that of the lower. Further, there was only partial inhibition of k 1 and k 2 , which showed two parallel pathways of aggregation, one via a state that requires unfolding of the protein and the other of partial unfolding with the ligand still bound. Inhibition kinetics of ligands provides a useful tool for probing an aggregation mechanism.amyloid | misfolding | folding | cancer T he most frequently mutated gene in cancer is that of the tumor suppressor p53. Some 70% of types of human cancers have their p53 directly inactivated by mutation, and so its reactivation is an important therapeutic goal (1). The most common oncogenic mutations are of residues in the DNA binding domain (DBD, residues 94-312) that make direct contact with DNA (2). But about 30%-40% of oncogenic mutants are inactivated because the mutations lower the stability of the DBD so that it denatures at body temperature, although it can be fully active at lower temperatures (3-6). We are attempting to rescue those temperature-sensitive mutants of p53 by designing small molecules that bind specifically to the native state of the protein and stabilize it (7). The rationale is that small molecules that bind to the native state of a temperature-sensitive mutant and not the denatured states will raise the melting temperature by a mass action effect. Such a molecule will slow down the rate of unfolding if it binds weakly to the transition state for unfolding. The obvious binding sites to target are those already present that bind natural ligands. In theory, they can be targeted in a chaperone strategy in which a rescue drug will compete for a binding site (7). We have chosen, instead, as a particularly useful paradigm for these studies, the stability of the p53 mutant Y220C, because the mutation induces a druggable cavity that is remote from functional areas of the protein (8, 9). We have designed small molecules that raise the apparent T m of ...

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“…Indeed, detection of p53 by immunohistochemistry in tumors is considered an indication of a mutation (Hall et al, 1991). Although the mechanisms of stabilization of mutant p53 are not clear, altered conformation, oligomerization, and interaction with other proteins like hsp70 have been proposed as potential explanations (Finlay et al, 1988;Sturzbecher et al, 1988;Kraiss et al, 1991). However, stabilization is not solely a property of mutant p53 protein, since it can also occur with wild-type p53 following a variety of stimuli, and these can result in either a decrease or an increase in function (Table 1).…”

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Loss of function and p53 protein stabilization

Blagosklonny

1997

Oncogene

127

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Wild-type (wt) p53 protein is rapidly degraded, has a short half-life and low intracellular levels. Stabilization of wt p53 protein following an appropriate stimulus (for example DNA damage) is a physiological regulation to increase function. In contrast, stabilization of p53 protein in the absence of a stimulus is always a hallmark of loss of function secondary to a mutation, or interaction with viral or cellular oncoproteins. It is generally accepted that stability of p53 protein depends on its intrinsic biochemical properties such as conformation or protein/protein interactions. However, I will discuss evidence that the stability of p53 is not a consequence of its intrinsic properties, but instead is determined by feedback control of its function. In the absence of an appropriate stimulus, a cell needs to keep p53 levels low, since increased levels can lead to apoptosis. To precisely regulate p53 levels, a cell must sense its level; and sensing its transactivating function, is the simplest way to sense p53. Following an appropriate stimulus (for example, DNA damage), the cell senses a state of`relative' p53 de®ciency and adapts by reducing p53 degradation. When the state of p53 de®ciency is a consequence of a mutation or interaction with viral oncoproteins, the cell does not sense p53, and again attempts to adapt by reducing p53 degradation. However, in the latter case, the increase in levels does not restore function, and the adaptation continues until degradation of p53 protein is maximally inhibited. In this case, no further inhibition of degradation is possible after DNA-damage or pharmacological inhibition of proteasomes. Thus lack of wt p53 function always results in increased p53 levels and nonregulation.

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Correlation of metabolic stability and altered quaternary structure of oncoprotein p53 with cell transformation

Cited by 56 publications

References 32 publications

Immunohistochemical staining patterns of p53 can serve as a surrogate marker for TP53 mutations in ovarian carcinoma: an immunohistochemical and nucleotide sequencing analysis

Immunohistochemical staining patterns of p53 can serve as a surrogate marker for TP53 mutations in ovarian carcinoma: an immunohistochemical and nucleotide sequencing analysis

Kinetic mechanism of p53 oncogenic mutant aggregation and its inhibition

Loss of function and p53 protein stabilization

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