Browsing by Author "Kim, Jin-Hee"

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    BAP1 is a novel regulator of HIF-1α
    (PNAS, 2023) Bononi, Angela; Wang, Qian; Zolondick, Alicia A.; Bai, Fang; Steele-Tanji, Mika; Suarez, Joelle S.; Pastorino, Sandra; Sipes, Abigail; Signorato, Valentina; Ferro, Angelica; Novelli, Flavia; Kim, Jin-Hee; Minaai, Michael; Takinishi, Yasutaka; Pellegrini, Laura; Napolitano, Andrea; Xu, Ronghui; Farrar, Christine; Goparaju, Chandra; Bassi, Cristian; Negrini, Massimo; Pagano, Ian; Sakamoto, Greg; Gaudino, Giovanni; Pass, Harvey I.; Onuchic, José N.; Yang, Haining; Carbone, Michele; Center for Theoretical Biological Physics
    BAP1 is a powerful tumor suppressor gene characterized by haplo insufficiency. Individuals carrying germline BAP1 mutations often develop mesothelioma, an aggressive malignancy of the serosal layers covering the lungs, pericardium, and abdominal cavity. Intriguingly, mesotheliomas developing in carriers of germline BAP1 mutations are less aggressive, and these patients have significantly improved survival. We investigated the apparent paradox of a tumor suppressor gene that, when mutated, causes less aggressive mesotheliomas. We discovered that mesothelioma biopsies with biallelic BAP1 mutations showed loss of nuclear HIF-1α staining. We demonstrated that during hypoxia, BAP1 binds, deubiquitylates, and stabilizes HIF-1α, the master regulator of the hypoxia response and tumor cell invasion. Moreover, primary cells from individuals carrying germline BAP1 mutations and primary cells in which BAP1 was silenced using siRNA had reduced HIF-1α protein levels in hypoxia. Computational modeling and co-immunoprecipitation experiments revealed that mutations of BAP1 residues I675, F678, I679, and L691 -encompassing the C-terminal domain-nuclear localization signal- to A, abolished the interaction with HIF-1α. We found that BAP1 binds to the N-terminal region of HIF-1α, where HIF-1α binds DNA and dimerizes with HIF-1β forming the heterodimeric transactivating complex HIF. Our data identify BAP1 as a key positive regulator of HIF-1α in hypoxia. We propose that the significant reduction of HIF-1α activity in mesothelioma cells carrying biallelic BAP1 mutations, accompanied by the significant reduction of HIF-1α activity in hypoxic tissues containing germline BAP1 mutations, contributes to the reduced aggressiveness and improved survival of mesotheliomas developing in carriers of germline BAP1 mutations.
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    Germline BARD1 variants predispose to mesothelioma by impairing DNA repair and calcium signaling
    (National Academy of Sciences, 2024) Novelli, Flavia; Yoshikawa, Yoshie; Vitto, Veronica Angela Maria; Modesti, Lorenzo; Minaai, Michael; Pastorino, Sandra; Emi, Mitsuru; Kim, Jin-Hee; Kricek, Franz; Bai, Fang; Onuchic, José N.; Bononi, Angela; Suarez, Joelle S.; Tanji, Mika; Favaron, Cristina; Zolondick, Alicia A.; Xu, Ronghui; Takanishi, Yasutaka; Wang, Zhanwei; Sakamoto, Greg; Gaudino, Giovanni; Grzymski, Joseph; Grosso, Federica; Schrump, David S.; Pass, Harvey I.; Atanesyan, Lilit; Smout, Jan; Savola, Suvi; Sarin, Kavita Y.; Abolhassani, Hassan; Hammarström, Lennart; Pan-Hammarström, Qiang; Giorgi, Carlotta; Pinton, Paolo; Yang, Haining; Carbone, Michele; Center for Theoretical Biological Physics
    We report that ~1.8% of all mesothelioma patients and 4.9% of those younger than 55, carry rare germline variants of the BRCA1 associated RING domain 1 (BARD1) gene that were predicted to be damaging by computational analyses. We conducted functional assays, essential for accurate interpretation of missense variants, in primary fibroblasts that we established in tissue culture from a patient carrying the heterozygous BARD1V523A mutation. We found that these cells had genomic instability, reduced DNA repair, and impaired apoptosis. Investigating the underlying signaling pathways, we found that BARD1 forms a trimeric protein complex with p53 and SERCA2 that regulates calcium signaling and apoptosis. We validated these findings in BARD1-silenced primary human mesothelial cells exposed to asbestos. Our study elucidated mechanisms of BARD1 activity and revealed that heterozygous germline BARD1 mutations favor the development of mesothelioma and increase the susceptibility to asbestos carcinogenesis. These mesotheliomas are significantly less aggressive compared to mesotheliomas in asbestos workers.