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Accumulation of wild-type p53 protein in progressive multifocal leukoencephalopathy: a flow of cytometry and DNA
A Ariza1, C von Uexküll-Güldeband, J L Mate
1Department of Pathology, Hospital Germans Trias i Pujol, Autonomous University of Barcelona, Spain.
Abstract:
p52 protein accumulation in JC virus (JCV)-infected cells of progressive multifocal leukoencephalopathy (PML) has been previously shown. Since many viral proteins are known to bind and stabilize p53, we are addressing the question of whether p53 protein accumulation in PML is the result of its sequestration by JCV and not the outcome of a p53 gene mutation which would prolong its half-life. We have investigated the status of the p53 gene in frozen autopsy brain samples from five PML patients. After isolating genomic DNA, p53 gene exons 2 through 9 were amplified and sequenced. No discrepancies were found in the DNA sequences of exons 2 through 9 and their intron/exon barriers when compared to those published for wild-type p53. On the other hand, dual (p53/DNA) flow cytometry analysis revealed p53 expression above that of the isotypic controls for each case. No aneuploid populations could be identified, however, which seems at odds with the aneuploid status normally associated with mutation-induced p53 dysfunction. These results indicate that the p53 gene harbors no mutations in PML and provide further evidence of p53 protein accumulation in this condition. Since p53 protein buildup in JCV-infected cells is not the consequence of a mutagenic interaction between JCV and the cell genome, we propose instead that p53 accumulation results from its binding and stabilization by JCV T protein.
Insights
p53 protein accumulates in progressive multifocal leukoencephalopathy (PML) but the gene is not mutated. JC virus (JCV) T protein likely stabilizes p53, causing its buildup in PML.
Area of Science:
- Neurovirology
- Molecular Biology
- Oncogenesis
Background:
- Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system caused by JC virus (JCV).
- p53 protein accumulation has been observed in JCV-infected PML cells, but the underlying mechanism remains unclear.
- Viral proteins are known to interact with and stabilize p53, a critical tumor suppressor protein.
Purpose of the Study:
- To investigate whether p53 protein accumulation in PML is due to p53 gene mutation or sequestration by JCV.
- To analyze the p53 gene status in PML patient brain samples.
- To determine the mechanism of p53 protein accumulation in JCV-infected cells.
Main Methods:
- Genomic DNA isolation from frozen PML autopsy brain samples.
- PCR amplification and sequencing of p53 gene exons 2-9 and intron/exon boundaries.
- Dual (p53/DNA) flow cytometry for p53 expression analysis.
Main Results:
- No mutations were detected in the sequenced exons and intron/exon barriers of the p53 gene in PML samples.
- Flow cytometry revealed elevated p53 protein expression in PML cases compared to controls.
- No aneuploid cell populations were identified, which contrasts with typical mutation-induced p53 dysfunction.
Conclusions:
- The p53 gene is not mutated in PML.
- p53 protein accumulates in PML, independent of genetic mutation.
- JCV T protein is proposed to bind and stabilize p53, leading to its accumulation in JCV-infected cells.