Over 50% of all human cancers lose p53 function. To evaluate the role of aggregation in cancer, we asked whether wild-type (WT) p53 and the hot-spot mutant R248Q could aggregate as amyloids under physiological conditions and whether the mutant could seed aggregation of the wild-type form. The central domains (p53C) of both constructs aggregated into a mixture of oligomers and fibrils. R248Q had a greater tendency to aggregate than WT p53. Full-length p53 aggregated into amyloid-like species that bound thioflavin T. The amyloid nature of the aggregates was demonstrated using x-ray diffraction, electron microscopy, FTIR, dynamic light scattering, cell viabilility assay, and anti-amyloid immunoassay. The x-ray diffraction pattern of the fibrillar aggregates was consistent with the typical conformation of cross β-sheet amyloid fibers with reflexions of 4.7 Å and 10 Å. A seed of R248Q p53C amyloid oligomers and fibrils accelerated the aggregation of WT p53C, a behavior typical of a prion. The R248Q mutant co-localized with amyloid-like species in a breast cancer sample, which further supported its prion-like effect. A tumor cell line containing mutant p53 also revealed massive aggregation of p53 in the nucleus. We conclude that aggregation of p53 into a mixture of oligomers and fibrils sequestrates the native protein into an inactive conformation that is typical of a prionoid. This prion-like behavior of oncogenic p53 mutants provides an explanation for the negative dominance effect and may serve as a potential target for cancer therapy. © 2012 by The American Society for Biochemistry and Molecular Biology, Inc.287332815228162Vousden, K.H., Lane, D.P., p53 in health and disease (2007) Nat. Rev. Mol. Cell Biol., 8, pp. 275-283Joerger, A.C., Fersht, A.R., Structural biology of the tumor suppressor p53 (2008) Annu. Rev. Biochem., 77, pp. 557-582Ishimaru, D., Andrade, L.R., Teixeira, L.S., Quesado, P.A., Maiolino, L.M., Lopez, P.M., Cordeiro, Y., Silva, J.L., Fibrillar aggregates of the tumor suppressor p53 core domain (2003) Biochemistry, 42, pp. 9022-9027Silva, J.L., Vieira, T.C., Gomes, M.P., Ano Bom, A.P., Lima, L.M., Freitas, M.S., Ishimaru, D., Foguel, D., Ligand binding and hydration in protein misfolding: Insights from studies of prion and p53 tumor suppressor proteins (2010) Acc. Chem. Res., 43, pp. 271-279Galea, C., Bowman, P., Kriwacki, R.W., Disruption of an intermonomer salt bridge in the p53 tetramerization domain results in an increased propensity to form amyloid fibrils (2005) Prot. Sci., 14, pp. 2993-3003Higashimoto, Y., Asanomi, Y., Takakusagi, S., Lewis, M.S., Uosaki, K., Durell, S.R., Anderson, C.W., Sakaguchi, K., Unfolding, aggregation, and amyloid formation by the tetramerization domain from mutant p53 associated with lung cancer (2006) Biochemistry, 45, pp. 1608-1619Rigacci, S., Bucciantini, M., Relini, A., Pesce, A., Gliozzi, A., Berti, A., Stefani, M., The (1-63) region of the p53 transactivation domain aggregates in vitro into cytotoxic amyloid assemblies (2008) Biophys. J., 94, pp. 3635-3646Ishimaru, D., Ano Bom, A.P., Lima, L.M., Quesado, P.A., Oyama, M.F., De Moura Gallo, C.V., Cordeiro, Y., Silva, J.L., Cognate DNA stabilizes the tumor suppressor p53 and prevents misfolding and aggregation (2009) Biochemistry, 48, pp. 6126-6135Levy, C.B., Stumbo, A.C., Ano Bom, A.P., Portari, E.A., Cordeiro, Y., Silva, J.L., De Moura-Gallo, C.V., Co-localization of mutant p53 and amyloid-like protein aggregates in breast tumors (2011) Int. J. Biochem. Cell Biol., 43, pp. 60-64Xu, J., Reumers, J., Couceiro, J.R., De Smet, F., Gallardo, R., Rudyak, S., Cornelis, A., Schymkowitz, J., Gain of function of mutant p53 by coaggregation with multiple tumor suppressors (2011) Nat. Chem. Biol., 7, pp. 285-295Chiti, F., Dobson, C.M., Protein misfolding, functional amyloid, and human disease (2006) Annu. Rev. Biochem., 75, pp. 333-366Pastore, A., Temussi, P.A., The two faces of Janus: Functional interactions and protein aggregation (2012) Curr. Opin. Struct. Biol., 22, pp. 30-37Butler, J.S., Loh, S.N., Structure, function, and aggregation of the zinc-free form of the p53 DNA binding domain (2003) Biochemistry, 42, pp. 2396-2403Antony, H., Wiegmans, A.P., Wei, M.Q., Chernoff, Y.O., Khanna, K.K., Munn, A.L., Potential roles for prions and protein-only inheritance in cancer (2011) Cancer Metastasis Rev., 31, pp. 1-19Hollstein, M., Sidransky, D., Vogelstein, B., Harris, C.C., p53 mutations in human cancers (1991) Science, 253, pp. 49-53Olivier, M., Hollstein, M., Hainaut, P., TP53 mutations in human cancers: Origins, consequences, and clinical use (2010) Cold Spring Harb. Perspect. Biol., 2, pp. a001008Cordeiro, Y., Kraineva, J., Gomes, M.P., Lopes, M.H., Martins, V.R., Lima, L.M., Foguel, D., Silva, J.L., The amino-terminal PrP domain is crucial to modulate prion misfolding and aggregation (2005) Biophys. J., 89, pp. 2667-2676Cordeiro, Y., Kraineva, J., Ravindra, R., Lima, L.M., Gomes, M.P., Foguel, D., Winter, R., Silva, J.L., Hydration and packing effects on prion folding and β-sheet conversion. High pressure spectroscopy and pressure perturbation calorimetry studies (2004) J. Biol. Chem., 279, pp. 32354-33259Glabe, C.G., Conformation-dependent antibodies target diseases of protein misfolding (2004) Trends Biochem. Sci., 29, pp. 542-547Lai, Z., Colón, W., Kelly, J.W., The acid-mediated denaturation pathway of transthyretin yields a conformational intermediate that can self-assemble into amyloid (1996) Biochemistry, 35, pp. 6470-6482Howie, A.J., Brewer, D.B., Howell, D., Jones, A.P., Physical basis of colors seen in Congo red-stained amyloid in polarized light (2008) Lab. Invest., 88, pp. 232-242Moll, U.M., LaQuaglia, M., Bénard, J., Riou, G., Wild-type p53 protein undergoes cytoplasmic sequestration in undifferentiated neuroblastomas but not in differentiated tumors (1995) Proc. Natl. Acad. Sci. U.S.A., 92, pp. 4407-4411Ostermeyer, A.G., Runko, E., Winkfield, B., Ahn, B., Moll, U.M., Cytoplasmically sequestered wild-type p53 protein in neuroblastoma is relocated to the nucleus by a C-terminal peptide (1996) Proc. Natl. Acad. Sci. U.S.A., 93, pp. 15190-15194Bom, A.P., Freitas, M.S., Moreira, F.S., Ferraz, D., Sanches, D., Gomes, A.M., Valente, A.P., Silva, J.L., The p53 core domain is a molten globule at low pH: Functional implications of a partially unfolded structure (2010) J. Biol. Chem., 285, pp. 2857-2866Gerweck, L.E., Tumor pH: Implications for treatment and novel drug design (1998) Semin. Radiat. Oncol., 8, pp. 176-182Gomes, M.P., Millen, T.A., Ferreira, P.S.E., Silva, N.L., Vieira, T.C., Almeida, M.S., Silva, J.L., Cordeiro, Y., Prion protein complexed to N2a cellular RNAs through its N-terminal domain forms aggregates and is toxic to murine neuroblastoma cells (2008) J. Biol. Chem., 283, pp. 19616-19625Ishimaru, D., Lima, L.M., Maia, L.F., Lopez, P.M., Ano Bom, A.P., Valente, A.P., Silva, J.L., Reversible aggregation plays a crucial role on the folding landscape of p53 core domain (2004) Biophys. J., 87, pp. 2691-2700Sunde, M., Serpell, L.C., Bartlam, M., Fraser, P.E., Pepys, M.B., Blake, C.C., Common core structure of amyloid fibrils by synchrotron X-ray diffraction (1997) J. Mol. Biol., 273, pp. 729-739Novitskaya, V., Bocharova, O.V., Bronstein, I., Baskakov, I.V., Amyloid fibrils of mammalian prion protein are highly toxic to cultured cells and primary neurons (2006) J. Biol. Chem., 281, pp. 13828-13836Vieira, M.N., Forny-Germano, L., Saraiva, L.M., Sebollela, A., Martinez, A.M., Houzel, J.C., De Felice, F.G., Ferreira, S.T., Soluble oligomers from a non-disease related protein mimic Aβ-induced tau hyperphosphorylation and neurodegeneration (2007) J. Neurochem., 103, pp. 736-748Gomes, M.P., Cordeiro, Y., Silva, J.L., The peculiar interaction between mammalian prion protein and RNA (2008) Prion, 2, pp. 64-66Elledge, R.M., Clark, G.M., Fuqua, S.A., Yu, Y.Y., Allred, D.C., p53 protein accumulation detected by five different antibodies: Relationship to prognosis and heat shock protein 70 in breast cancer (1994) Cancer Res., 54, pp. 3752-3757Moll, U.M., Valea, F., Chumas, J., Role of p53 alteration in primary peritoneal carcinoma (1997) Int. J. Gynecol. Pathol., 16, pp. 156-162Lambert, M.P., Barlow, A.K., Chromy, B.A., Edwards, C., Freed, R., Liosatos, M., Morgan, T.E., Klein, W.L., Diffusible, nonfibrillar ligands derived from Abeta1-42 are potent central nervous system neurotoxins (1998) Proc. Natl. Acad. Sci. U.S.A., 95, pp. 6448-6453Kayed, R., Head, E., Thompson, J.L., McIntire, T.M., Milton, S.C., Cotman, C.W., Glabe, C.G., Common structure of soluble amyloid oligomers implies common mechanism of pathogenesis (2003) Science, 300, pp. 486-489Gottifredi, V., Prives, C., Molecular biology. Getting p53 out of the nucleus (2001) Science, 292, pp. 1851-1852Soussi, T., Béroud, C., Assessing TP53 status in human tumours to evaluate clinical outcome (2001) Nat. Rev. Cancer, 1, pp. 233-240Chowdary, D.R., Dermody, J.J., Jha, K.K., Ozer, H.L., Accumulation of p53 in a mutant cell line defective in the ubiquitin pathway (1994) Mol. Cell Biol., 14, pp. 1997-2003Chen, L., Lu, W., Agrawal, S., Zhou, W., Zhang, R., Ubiquitous induction of p53 in tumor cells by antisense inhibition of MDM2 expression (1999) Mol. Med., 5, pp. 21-34Goh, A.M., Coffill, C.R., Lane, D.P., The role of mutant p53 in human cancer (2011) J. Pathol., 223, pp. 116-126Joerger, A.C., Rajagopalan, S., Natan, E., Veprintsev, D.B., Robinson, C.V., Fersht, A.R., Structural evolution of p53, p63, and p73: Implication for heterotetramer formation (2009) Proc. Natl. Acad. Sci. U.S.A., 106, pp. 17705-17710Nicholls, C.D., McLure, K.G., Shields, M.A., Lee, P.W., Biogenesis of p53 involves cotranslational dimerization of monomers and post-translational dimerization of dimers. Implications on the dominant negative effect (2002) J. Biol. Chem., 277, pp. 12937-12945Aguzzi, A., Rajendran, L., The transcellular spread of cytosolic amyloids, prions, and prionoids (2009) Neuron, 64, pp. 783-790Frost, B., Diamond, M.I., Prion-like mechanisms in neurodegenerative diseases (2010) Nat. Rev. Neurosci., 11, pp. 155-159Park, S.J., Borin, B.N., Martinez-Yamout, M.A., Dyson, H.J., The client protein p53 adopts a molten globule-like state in the presence of Hsp90 (2011) Nat. Struct. Mol. Biol., 18, pp. 537-541Kocisko, D.A., Vaillant, A., Lee, K.S., Arnold, K.M., Bertholet, N., Race, R.E., Olsen, E.A., Caughey, B., Potent antiscrapie activities of degenerate phosphorothioate oligonucleotides (2006) Antimicrob. Agents Chemother., 50, pp. 1034-1044Caughey, B., Caughey, W.S., Kocisko, D.A., Lee, K.S., Silveira, J.R., Morrey, J.D., Prions and transmissible spongiform encephalopathy (TSE) chemotherapeutics: A common mechanism for anti-TSE compounds? (2006) Acc. Chem. Res., 39, pp. 646-653Vieira, T.C., Reynaldo, D.P., Gomes, M.P., Almeida, M.S., Cordeiro, Y., Silva, J.L., Heparin binding by murine recombinant prion protein leads to transient aggregation and formation of RNA-resistant species (2010) J. Am. Chem. Soc., 133, pp. 334-344