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The p53 tumor suppressor is widely found to be mutated in human cancer. This protein is regarded as a molecular hub regulating different cell responses, namely cell death. Compelling data have demonstrated that the impairment of p53 activity correlates with tumor development and maintenance. For these reasons, the reactivation of p53 function is regarded as a promising strategy to halt cancer. In the present work, the recombinant mutant p53R280K DNA binding domain (DBD) was produced for the first time, and its crystal structure was determined in the absence of DNA to a resolution of 2.0 Å. The solved structure contains four molecules in the asymmetric unit, four zinc(II) ions, and 336 water molecules. The structure was compared with the wild-type p53 DBD structure, isolated and in complex with DNA. These comparisons contributed to a deeper understanding of the mutant p53R280K structure, as well as the loss of DNA binding related to halted transcriptional activity. The structural information derived may also contribute to the rational design of mutant p53 reactivating molecules with potential application in cancer treatment. ; We thank Gilberto Fronza (from Mutagenesi e Prevenzione Oncologica, Ospedale Policlinico San Martino, Genova, Italy), for providing us with the pLS76 vector. We acknowledge the European Synchrotron Radiation Facility for the provision of synchrotron radiation facilities and access to beamline ID30B. This work received financial support from the European Union (FEDER, Fundo Europeu de Desenvolvimento Regional, funds POCI/01/0145/FEDER/007728 through Programa Operacional Factores de Competitividade–COMPETE) and National Funds (FCT/MCTES, Fundação para a Ciência e Tecnologia and Ministério da Ciência, Tecnologia e Ensino Superior) under the Partnership Agreement PT2020 UID/MULTI/04378/2013, and projects (3599-PPCDT) PTDC/DTP-FTO/1981/2014–POCI-01-0145-FEDER-016581 and RECI/BBB-BEP/0124/2012. FCT fellowships: PD/BD/114046/2015 (Ana Sara Gomes) and SFRH/BD/96189/2013 (Sara Gomes) (thanks FCT PhD ...

PD/BD/114046/2015 SFRH/BD/96189/2013 SFRH/BPD/110640/2015 We thank Gilberto Fronza (from Mutagenesi e Prevenzione Oncologica, Ospedale Policlinico San Martino, Genova, Italy), for providing us with the pLS76 vector. We acknowledge the European Synchrotron Radiation Facility for the provision of synchrotron radiation facilities and access to beamline ID30B. This work received financial support from the European Union (FEDER, Fundo Europeu de Desenvolvimento Regional, funds POCI/01/0145/FEDER/007728 through Programa Operacional Factores de Competitividade–COMPETE) and National Funds (FCT/MCTES, Fundação para a Ciência e Tecnologia and Ministério da Ciência, Tecnologia e Ensino Superior) under the Partnership Agreement PT2020 UID/MULTI/04378/2013, and projects (3599-PPCDT) PTDC/DTP-FTO/1981/2014–POCI-01-0145-FEDER-016581 and RECI/BBB-BEP/0124/2012. FCT fellowships: PD/BD/114046/2015 (Ana Sara Gomes) and SFRH/BD/96189/2013 (Sara Gomes) (thanks FCT PhD Doctoral Programme BiotechHealth), and SFRH/BPD/110640/2015 (Carla Oliveira). ; The p53 tumor suppressor is widely found to be mutated in human cancer. This protein is regarded as a molecular hub regulating different cell responses, namely cell death. Compelling data have demonstrated that the impairment of p53 activity correlates with tumor development and maintenance. For these reasons, the reactivation of p53 function is regarded as a promising strategy to halt cancer. In the present work, the recombinant mutant p53R280K DNA binding domain (DBD) was produced for the first time, and its crystal structure was determined in the absence of DNA to a resolution of 2.0 Å. The solved structure contains four molecules in the asymmetric unit, four zinc(II) ions, and 336 water molecules. The structure was compared with the wild-type p53 DBD structure, isolated and in complex with DNA. These comparisons contributed to a deeper understanding of the mutant p53R280K structure, as well as the loss of DNA binding related to halted transcriptional activity. The structural information derived may also contribute to the rational design of mutant p53 reactivating molecules with potential application in cancer treatment. ; publishersversion ; published

Half of human cancers harbor TP53 mutations that render p53 inactive as a tumor suppressor. In these cancers, reactivation of mutant p53 (mutp53) through restoration of wild-type-like function constitutes a valuable anticancer therapeutic strategy. In order to search for mutp53 reactivators, a small library of tryptophanol-derived oxazoloisoindolinones was synthesized and the potential of these compounds as mutp53 reactivators and anticancer agents was investigated in human tumor cells and xenograft mouse models. By analysis of their anti-proliferative effect on a panel of p53-null NCI-H1299 tumor cells ectopically expressing highly prevalent mutp53, the compound SLMP53-2 was selected based on its potential reactivation of multiple structural mutp53. In mutp53-Y220C-expressing hepatocellular carcinoma (HCC) cells, SLMP53-2-induced growth inhibition was mediated by cell cycle arrest, apoptosis, and endoplasmic reticulum stress response. In these cells, SLMP53-2 restored wild-type-like conformation and DNA-binding ability of mutp53-Y220C by enhancing its interaction with the heat shock protein 70 (Hsp70), leading to the reestablishment of p53 transcriptional activity. Additionally, SLMP53-2 displayed synergistic effect with sorafenib, the only approved therapy for advanced HCC. Notably, it exhibited potent antitumor activity in human HCC xenograft mouse models with a favorable toxicological profile. Collectively, SLMP53-2 is a new mutp53-targeting agent with promising antitumor activity, particularly against HCC. ; Authors acknowledge the financial support from European Union (FEDER funds POCI/01/0145/FEDER/007728 through Programa Operacional Factores de Competitividade—COMPETE) and National Funds (FCT/MEC, Fundação para a Ciência e Tecnologia and Ministério da Educação e Ciência) under the Partnership Agreement UID/DTP/04138/2019 (iMed.ULisboa), UID/NEU/04539/2013, UID/NEU/04539/2019. CENTRO-01-0145-FEDER-000012-HealthyAging2020, UID/BIO/04469/2019, BioTecNorte operation (NORTE-01-0145-FEDER-000004), and the ...