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Tushar Patel - One of the best experts on this subject based on the ideXlab platform.
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BAP1 dependent expression of long non-coding RNA NEAT-1 contributes to sensitivity to gemcitabine in cholangiocarcinoma
Molecular Cancer, 2017Co-Authors: Mansi Parasramka, Irene K. Yan, Catherine Foye, Yan Asmann, Sayantan Maji, Akiko Matsuda, Phuong Nguyen, Xue Wang, Tushar PatelAbstract:BackgroundGenetic alterations in chromatin modulators such as BRCA-1 associated protein-1 (BAP1) are the most frequent genetic alteration in intrahepatic cholangiocarcinomas (CCA). We evaluated the contribution of BAP1 expression on tumor cell behavior and therapeutic sensitivity to identify rationale therapeutic strategies.MethodsThe impact of BAP1 expression on sensitivity to therapeutic agents was evaluated in CCA cells with a 7-fold difference in BAP1 expression (KMBC-low, HuCCT1-high) and genetically engineered haplo-insufficient BAP1 knockout cells. We also identified long non-coding RNA genes associated with loss of BAP1 and their role in therapeutic sensitivity.ResultsSensitivity to gemcitabine was greater in low BAP1 expressing or BAP1 knockout cells compared with the high BAP1 expressing cells or control haplo-insufficient cells respectively. Similar results were observed with TSA, olaparib, b-AP15 but not with GSK126. A differential synergistic effect was observed in combinations of gemcitabine with olaparib or GSK126 in KMBC cells and TSA or BAP15 in HuCCT1 cells, indicating BAP1 dependent target-specific synergism and sensitivity to gemcitabine. A BAP1 dependent alteration in expression of lncRNA NEAT-1 was identified by RT-PCR based lncRNA expression profiling, and an inverse relationship between this lncRNA and BAP1 was observed in analysis of the Tumor Cancer Genome Atlas cholangiocarcinoma dataset. Exogenous modulation of NEAT-1 and/or BAP1 expression altered tumor cell phenotype and modulated sensitivity to gemcitabine.ConclusionsNEAT-1 is a downstream effector of gemcitabine sensitivity in CCA. The expression of BAP1 is a determinant of sensitivity to therapeutic drugs that can be exploited to enhance responses through combination strategies.
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BAP1 dependent expression of long non coding rna neat 1 contributes to sensitivity to gemcitabine in cholangiocarcinoma
Molecular Cancer, 2017Co-Authors: Mansi Parasramka, Catherine Foye, Yan Asmann, Sayantan Maji, Akiko Matsuda, Xue Wang, Phuong L Nguyen, Tushar PatelAbstract:Genetic alterations in chromatin modulators such as BRCA-1 associated protein-1 (BAP1) are the most frequent genetic alteration in intrahepatic cholangiocarcinomas (CCA). We evaluated the contribution of BAP1 expression on tumor cell behavior and therapeutic sensitivity to identify rationale therapeutic strategies. The impact of BAP1 expression on sensitivity to therapeutic agents was evaluated in CCA cells with a 7-fold difference in BAP1 expression (KMBC-low, HuCCT1-high) and genetically engineered haplo-insufficient BAP1 knockout cells. We also identified long non-coding RNA genes associated with loss of BAP1 and their role in therapeutic sensitivity. Sensitivity to gemcitabine was greater in low BAP1 expressing or BAP1 knockout cells compared with the high BAP1 expressing cells or control haplo-insufficient cells respectively. Similar results were observed with TSA, olaparib, b-AP15 but not with GSK126. A differential synergistic effect was observed in combinations of gemcitabine with olaparib or GSK126 in KMBC cells and TSA or BAP15 in HuCCT1 cells, indicating BAP1 dependent target-specific synergism and sensitivity to gemcitabine. A BAP1 dependent alteration in expression of lncRNA NEAT-1 was identified by RT-PCR based lncRNA expression profiling, and an inverse relationship between this lncRNA and BAP1 was observed in analysis of the Tumor Cancer Genome Atlas cholangiocarcinoma dataset. Exogenous modulation of NEAT-1 and/or BAP1 expression altered tumor cell phenotype and modulated sensitivity to gemcitabine. NEAT-1 is a downstream effector of gemcitabine sensitivity in CCA. The expression of BAP1 is a determinant of sensitivity to therapeutic drugs that can be exploited to enhance responses through combination strategies.
Mansi Parasramka - One of the best experts on this subject based on the ideXlab platform.
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BAP1 dependent expression of long non-coding RNA NEAT-1 contributes to sensitivity to gemcitabine in cholangiocarcinoma
Molecular Cancer, 2017Co-Authors: Mansi Parasramka, Irene K. Yan, Catherine Foye, Yan Asmann, Sayantan Maji, Akiko Matsuda, Phuong Nguyen, Xue Wang, Tushar PatelAbstract:BackgroundGenetic alterations in chromatin modulators such as BRCA-1 associated protein-1 (BAP1) are the most frequent genetic alteration in intrahepatic cholangiocarcinomas (CCA). We evaluated the contribution of BAP1 expression on tumor cell behavior and therapeutic sensitivity to identify rationale therapeutic strategies.MethodsThe impact of BAP1 expression on sensitivity to therapeutic agents was evaluated in CCA cells with a 7-fold difference in BAP1 expression (KMBC-low, HuCCT1-high) and genetically engineered haplo-insufficient BAP1 knockout cells. We also identified long non-coding RNA genes associated with loss of BAP1 and their role in therapeutic sensitivity.ResultsSensitivity to gemcitabine was greater in low BAP1 expressing or BAP1 knockout cells compared with the high BAP1 expressing cells or control haplo-insufficient cells respectively. Similar results were observed with TSA, olaparib, b-AP15 but not with GSK126. A differential synergistic effect was observed in combinations of gemcitabine with olaparib or GSK126 in KMBC cells and TSA or BAP15 in HuCCT1 cells, indicating BAP1 dependent target-specific synergism and sensitivity to gemcitabine. A BAP1 dependent alteration in expression of lncRNA NEAT-1 was identified by RT-PCR based lncRNA expression profiling, and an inverse relationship between this lncRNA and BAP1 was observed in analysis of the Tumor Cancer Genome Atlas cholangiocarcinoma dataset. Exogenous modulation of NEAT-1 and/or BAP1 expression altered tumor cell phenotype and modulated sensitivity to gemcitabine.ConclusionsNEAT-1 is a downstream effector of gemcitabine sensitivity in CCA. The expression of BAP1 is a determinant of sensitivity to therapeutic drugs that can be exploited to enhance responses through combination strategies.
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BAP1 dependent expression of long non coding rna neat 1 contributes to sensitivity to gemcitabine in cholangiocarcinoma
Molecular Cancer, 2017Co-Authors: Mansi Parasramka, Catherine Foye, Yan Asmann, Sayantan Maji, Akiko Matsuda, Xue Wang, Phuong L Nguyen, Tushar PatelAbstract:Genetic alterations in chromatin modulators such as BRCA-1 associated protein-1 (BAP1) are the most frequent genetic alteration in intrahepatic cholangiocarcinomas (CCA). We evaluated the contribution of BAP1 expression on tumor cell behavior and therapeutic sensitivity to identify rationale therapeutic strategies. The impact of BAP1 expression on sensitivity to therapeutic agents was evaluated in CCA cells with a 7-fold difference in BAP1 expression (KMBC-low, HuCCT1-high) and genetically engineered haplo-insufficient BAP1 knockout cells. We also identified long non-coding RNA genes associated with loss of BAP1 and their role in therapeutic sensitivity. Sensitivity to gemcitabine was greater in low BAP1 expressing or BAP1 knockout cells compared with the high BAP1 expressing cells or control haplo-insufficient cells respectively. Similar results were observed with TSA, olaparib, b-AP15 but not with GSK126. A differential synergistic effect was observed in combinations of gemcitabine with olaparib or GSK126 in KMBC cells and TSA or BAP15 in HuCCT1 cells, indicating BAP1 dependent target-specific synergism and sensitivity to gemcitabine. A BAP1 dependent alteration in expression of lncRNA NEAT-1 was identified by RT-PCR based lncRNA expression profiling, and an inverse relationship between this lncRNA and BAP1 was observed in analysis of the Tumor Cancer Genome Atlas cholangiocarcinoma dataset. Exogenous modulation of NEAT-1 and/or BAP1 expression altered tumor cell phenotype and modulated sensitivity to gemcitabine. NEAT-1 is a downstream effector of gemcitabine sensitivity in CCA. The expression of BAP1 is a determinant of sensitivity to therapeutic drugs that can be exploited to enhance responses through combination strategies.
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clear cell renal cell carcinoma subtypes identified by BAP1 and pbrm1 expression
The Journal of Urology, 2016Co-Authors: Richard W. Joseph, Daniel J Serie, Alexander S Parker, Eugene P Frenkel, Mansi Parasramka, Thai H Ho, John C. Cheville, Payal Kapur, James BrugarolasAbstract:Purpose: In clear cell renal cell carcinoma BAP1 and PBRM1 are 2 of the most commonly mutated genes (10% to 15% and 40% to 50%, respectively). We sought to determine the prognostic significance of PBRM1 and BAP1 expression in clear cell renal cell carcinoma.Materials and Methods: We used immunohistochemistry to assess PBRM1 protein expression in 1,479 primary clear cell renal cell carcinoma tumors that were previously stained for BAP1. A centralized pathologist reviewed all cases and categorized tumors as positive or deficient for PBRM1 and BAP1. Kaplan-Meier and Cox regression models were used to evaluate association of PBRM1 and BAP1 expression with the risk of death from renal cell carcinoma and the risk of metastasis after adjustment for age and the Mayo Clinic SSIGN (stage, size, grade and necrosis) score.Results: PBRM1 and BAP1 expression was PBRM1+ BAP1+ in 40.1% of tumors, PBRM1– BAP1+ in 48.6%, PBRM1+ BAP1– in 8.7% and PBRM1– BAP1– in 1.8%. The incidence of PBRM1 and BAP1 loss in the same tumor w...
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loss of BAP1 protein expression is an independent marker of poor prognosis in patients with low risk clear cell renal cell carcinoma
Cancer, 2014Co-Authors: Richard W. Joseph, Daniel J Serie, Eugene P Frenkel, Mansi Parasramka, Thai H Ho, John C. Cheville, Payal Kapur, Dinesh Rakheja, Jeanette E Eckelpassow, James BrugarolasAbstract:BACKGROUND The majority of patients diagnosed with clear cell renal cell carcinoma (ccRCC) have low-risk disease with a < 10% chance of ccRCC-specific death. DNA sequencing revealed that mutations in BAP1 (BRCA1 associated protein-1) occur in 5% to 15% of ccRCC cases and are associated with poor outcomes. The vast majority of BAP1 mutations abolish protein expression. In this study, we used a highly sensitive and specific immunohistochemistry (IHC) assay to test whether BAP1 expression is an independent marker of ccRCC-specific survival, particularly in patients with low-risk disease. METHODS BAP1 expression was assessed, using IHC, in 1479 patients who underwent nephrectomy to treat clinically localized ccRCC. A centralized pathologist dichotomized patients as either BAP1-positive or BAP1-negative. The authors employed Kaplan-Meier and Cox regression models to associate BAP1 expression with cancer-specific survival. RESULTS A total of 10.5% of tumors were BAP1-negative, 84.8% of tumors were BAP1-positive, and 4.6% of tumors had ambiguous staining for BAP1. Patients with BAP1-negative tumors have an increased risk of ccRCC-related death (hazard ratio [HR] = 3.06; 95% confidence interval [CI] = 2.28-4.10; P = 6.77 × 10−14). BAP1 expression remained an independent marker of prognosis after adjusting for the UCLA integrated staging system (UISS) (HR = 1.67; 95% CI = 1.24-2.25; P < .001). Finally, BAP1 was an independent prognostic marker in low-risk patients with a Mayo Clinic stage, size, grade, and necrosis (SSIGN) score of ≤ 3 (HR = 3.24; 95% CI = 1.26-8.33; P = .015). CONCLUSIONS This study used a large patient cohort to demonstrate that BAP1 expression is an independent marker of prognosis in patients with low-risk (SSIGN≤ 3) ccRCC. Cancer 2014;1059–1067. © 2014 American Cancer Society.
Sam M Janes - One of the best experts on this subject based on the ideXlab platform.
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s22 BAP1 expression and treatment outcomes in malignant pleural mesothelioma in a prospective uk based clinical trial
Thorax, 2017Co-Authors: Neelam Kumar, K Kolluri, Al D Rifai, Yuki Ishii, Elaine Borg, Mary Falzon, Andrew G Nicholson, Sam M JanesAbstract:Objectives Genomic studies of malignant pleural mesothelioma (MPM) have identified frequent mutations in the nuclear deubiquitinase BRCA Associated Protein 1 (BAP1). Previous studies have identified 100% correlation between BAP1 nuclear staining and wild type BAP1 status, pointing to immunohistochemistry (IHC) as a reliable technique to detect BAP1 molecular status. The objective of this study is to assess BAP1 expression and infer molecular status using IHC in a cohort from a prospective UK based clinical trial (MSO1). Furthermore, we aim to evaluate the effect of BAP1 status on treatment outcomes. Methods BAP1 expression was evaluated by IHC in 79 biopsies independently by two consultant histopathologists. Cases were considered positive (wild type BAP1) if strong nuclear staining was present and negative (mutant BAP1) if absent. Results Assessment of BAP1 expression was concordant in 77 of 79 cases (97%). BAP1 expression was negative in 66 of these 77 cases (86%). Patient characteristics and the effect of BAP1 expression on treatment outcomes are in Table 1. Conclusions BAP1 expression was negative in 86% of MPM tumours suggesting a high frequency of BAP1 mutations in this UK cohort. No significant differences in clinical characteristics or outcomes were noted between cases with positive or negative BAP1 expression overall. When analysed by treatment subgroup, there was a trend towards a survival benefit in cases with negative BAP1 expression (BAP1 mutants) in the ASC plus vinorelbine arm, but no statistically significant difference in outcomes within any treatment arm. We plan to further validate our findings by correlating BAP1 expression directly with BAP1 molecular status in this cohort using laser capture microdissection and sequencing.
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BAP1 expression and treatment outcomes in malignant mesothelioma
European Respiratory Journal, 2017Co-Authors: Neelam Kumar, K Kolluri, Elaine Borg, Mary Falzon, Andrew G Nicholson, Elizabeth K Sage, Sam M JanesAbstract:Objective: Genomic studies of malignant mesothelioma (MM) have identified frequent mutations in BRCA Associated Protein 1 (BAP1), a nuclear deubiquitinase and transcriptional regulator. Immunohistochemistry (IHC) is a reliable technique to determine BAP1 molecular status. Our objective is to assess BAP1 expression and infer molecular status in a cohort from a prospective UK clinical trial (MSO1) and to determine if BAP1 status is predictive of treatment outcomes. Method: BAP1 IHC was evaluated in 79 tumour biopsies by 2 histopathologists. Cases were considered positive (wild type BAP1) if strong nuclear staining was present and negative (mutant BAP1) if absent. Results: BAP1 expression was negative in 66 of these 77 cases (86%). Conclusions: BAP1 IHC was negative in 86% of tumours suggesting a high frequency of BAP1 mutations. There was no significant correlation in clinical characteristics or outcomes with BAP1 status. When analysed by treatment subgroup, there was a trend towards a survival benefit in cases with negative BAP1 expression (BAP1 mutants) in the ASC plus vinorelbine arm, but no statistically significant difference in outcomes within any treatment arm.
Salima Daou - One of the best experts on this subject based on the ideXlab platform.
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Monoubiquitination of ASXLs controls the deubiquitinase activity of the tumor suppressor BAP1
Nature Communications, 2018Co-Authors: Salima Daou, Haithem Barbour, Nadine Sen Nkwe, Oumaima Ahmed, Louis Masclef, Caroline Baril, Damehan Tchelougou, Maxime Uriarte, Eric Bonneil, Derek F. CeccarelliAbstract:The tumor suppressor and deubiquitinase (DUB) BAP1 and its Drosophila ortholog Calypso assemble DUB complexes with the transcription regulators Additional sex combs-like (ASXL1, ASXL2, ASXL3) and Asx respectively. ASXLs and Asx use their DEUBiquitinase ADaptor (DEUBAD) domain to stimulate BAP1/Calypso DUB activity. Here we report that monoubiquitination of the DEUBAD is a general feature of ASXLs and Asx. BAP1 promotes DEUBAD monoubiquitination resulting in an increased stability of ASXL2, which in turn stimulates BAP1 DUB activity. ASXL2 monoubiquitination is directly catalyzed by UBE2E family of Ubiquitin-conjugating enzymes and regulates mammalian cell proliferation. Remarkably, Calypso also regulates Asx monoubiquitination and transgenic flies expressing monoubiquitination-defective Asx mutant exhibit developmental defects. Finally, the protein levels of ASXL2, BAP1 and UBE2E enzymes are highly correlated in mesothelioma tumors suggesting the importance of this signaling axis for tumor suppression. We propose that monoubiquitination orchestrates a molecular symbiosis relationship between ASXLs and BAP1.
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the BAP1 asxl2 histone h2a deubiquitinase complex regulates cell proliferation and is disrupted in cancer
Journal of Biological Chemistry, 2015Co-Authors: Salima Daou, Ian Hammondmartel, Nazar Mashtalir, Haithem Barbour, Jessica Gagnon, Nicholas Victor Iannantuono, Nadine Sen Nkwe, Alena Motorina, Helen Yu, Hugo WurteleAbstract:Abstract The deubiquitinase (DUB) and tumor suppressor BAP1 catalyzes ubiquitin removal from histone H2A K119 and coordinates cell proliferation, but how BAP1 partners modulate its function remains poorly understood. Here, we report that BAP1 forms two mutually exclusive complexes with the transcriptional regulators ASXL1 and ASXL2, which are necessary for maintaining proper protein levels of this DUB. Conversely, BAP1 is essential for maintaining ASXL2, but not ASXL1 protein stability. Notably, cancer-associated loss of BAP1 expression results in ASXL2 destabilization and hence loss of its function. ASXL1 and ASXL2 use their ASXM domains to interact with the C-terminal domain (CTD) of BAP1 and these interactions are required for ubiquitin binding and H2A deubiquitination. The deubiquitination promoting effect of ASXM requires intramolecular interactions between catalytic and non-catalytic domains of BAP1 which generate a composite ubiquitin binding interface (CUBI). Notably, the CUBI engages multiple interactions with ubiquitin involving, (i) the ubiquitin carboxyl hydrolase (UCH) catalytic domain of BAP1 which interacts with the hydrophobic patch of ubiquitin and (ii) the CTD domain which interacts with a charged patch of ubiquitin. Significantly, we identified cancer-associated mutations of BAP1 that disrupt the CUBI, and notably an in frame deletion in the CTD that inhibits its interaction with ASXL1/2, DUB activity and deregulates cell proliferation. Moreover, we demonstrated that BAP1 interaction with ASXL2 regulates cell senescence and that ASXL2 cancer-associated mutations disrupt BAP1 DUB activity. Thus, inactivation of BAP1/ASXL2 axis might contribute to cancer development.
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autodeubiquitination protects the tumor suppressor BAP1 from cytoplasmic sequestration mediated by the atypical ubiquitin ligase ube2o
Molecular Cell, 2014Co-Authors: Nazar Mashtalir, Salima Daou, Ian Hammondmartel, Haithem Barbour, Jessica Gagnon, Marc Therrien, El Bachir AffarAbstract:The tumor suppressor BAP1 interacts with chromatin-associated proteins and regulates cell proliferation, but its mechanism of action and regulation remain poorly defined. We show that the ubiquitin-conjugating enzyme UBE2O multi-monoubiquitinates the nuclear localization signal of BAP1, thereby inducing its cytoplasmic sequestration. This activity is counteracted by BAP1 autodeubiquitination through intramolecular interactions. Significantly, we identified cancer-derived BAP1 mutations that abrogate autodeubiquitination and promote its cytoplasmic retention, indicating that BAP1 autodeubiquitination ensures tumor suppression. The antagonistic relationship between UBE2O and BAP1 is also observed during adipogenesis, whereby UBE2O promotes differentiation and cytoplasmic localization of BAP1. Finally, we established a putative targeting consensus sequence of UBE2O and identified numerous chromatin remodeling factors as potential targets, several of which tested positive for UBE2O-mediated ubiquitination. Thus, UBE2O defines an atypical ubiquitin-signaling pathway that coordinates the function of BAP1 and establishes a paradigm for regulation of nuclear trafficking of chromatin-associated proteins.
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tumor suppressor and deubiquitinase BAP1 promotes dna double strand break repair
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Helen Yu, Salima Daou, Ian Hammondmartel, Haithem Barbour, Elliot Drobetsky, Mehdi Ghram, Amelie Rodrigue, Luc Corbeil, Josee Hebert, Jeanyves MassonAbstract:The cellular response to highly genotoxic DNA double-strand breaks (DSBs) involves the exquisite coordination of multiple signaling and repair factors. Here, we conducted a functional RNAi screen and identified BAP1 as a deubiquitinase required for efficient assembly of the homologous recombination (HR) factors BRCA1 and RAD51 at ionizing radiation (IR) -induced foci. BAP1 is a chromatin-associated protein frequently inactivated in cancers of various tissues. To further investigate the role of BAP1 in DSB repair, we used a gene targeting approach to knockout (KO) this deubiquitinase in chicken DT40 cells. We show that BAP1-deficient cells are (i) sensitive to IR and other agents that induce DSBs, (ii) defective in HR-mediated immunoglobulin gene conversion, and (iii) exhibit an increased frequency of chromosomal breaks after IR treatment. We also show that BAP1 is recruited to chromatin in the proximity of a single site-specific I-SceI–induced DSB. Finally, we identified six IR-induced phosphorylation sites in BAP1 and showed that mutation of these residues inhibits BAP1 recruitment to DSB sites. We also found that both BAP1 catalytic activity and its phosphorylation are critical for promoting DNA repair and cellular recovery from DNA damage. Our data reveal an important role for BAP1 in DSB repair by HR, thereby providing a possible molecular basis for its tumor suppressor function.
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the ubiquitin carboxyl hydrolase BAP1 forms a ternary complex with yy1 and hcf 1 and is a critical regulator of gene expression
Molecular and Cellular Biology, 2010Co-Authors: Helen Yu, Frank J Rauscher, Salima Daou, Ian Hammondmartel, Nazar Mashtalir, Julie Ross, Gerald W Hart, Elliot Drobetsky, Eric Milot, El Bachir AffarAbstract:The candidate tumor suppressor BAP1 is a deubiquitinating enzyme (DUB) involved in the regulation of cell proliferation, although the molecular mechanisms governing its function remain poorly defined. BAP1 was recently shown to interact with and deubiquitinate the transcriptional regulator host cell factor 1 (HCF-1). Here we show that BAP1 assembles multiprotein complexes containing numerous transcription factors and cofactors, including HCF-1 and the transcription factor Yin Yang 1 (YY1). Through its coiled-coil motif, BAP1 directly interacts with the zinc fingers of YY1. Moreover, HCF-1 interacts with the middle region of YY1 encompassing the glycine-lysine-rich domain and is essential for the formation of a ternary complex with YY1 and BAP1 in vivo. BAP1 activates transcription in an enzymatic-activity-dependent manner and regulates the expression of a variety of genes involved in numerous cellular processes. We further show that BAP1 and HCF-1 are recruited by YY1 to the promoter of the cox7c gene, which encodes a mitochondrial protein used here as a model of BAP1-activated gene expression. Our findings (i) establish a direct link between BAP1 and the transcriptional control of genes regulating cell growth and proliferation and (ii) shed light on a novel mechanism of transcription regulation involving ubiquitin signaling.
Frank J Rauscher - One of the best experts on this subject based on the ideXlab platform.
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familial and somatic BAP1 mutations inactivate asxl1 2 mediated allosteric regulation of BAP1 deubiquitinase by targeting multiple independent domains
Cancer Research, 2017Co-Authors: Hongzhuang Peng, Jeremy W Prokop, Jayashree Karar, Kyewon Park, William J Harbour, Anne M Bowcock, Bruce S Malkowicz, Mitchell Cheung, Joseph R Testa, Frank J RauscherAbstract:Deleterious mutations of the ubiquitin carboxy-terminal hydrolase BAP1 found in cancers are predicted to encode inactive truncated proteins, suggesting that loss of enzyme function is a primary tumorigenic mechanism. However, many tumors exhibit missense mutations or in-frame deletions or insertions, often outside the functionally critical UCH domain in this tumor suppressor protein. Thus, precisely how these mutations inactivate BAP1 is unknown. Here, we show how these mutations affect BAP1 interactions with the Polycomb group-like protein ASXL2, using combinations of computational modeling technology, molecular biology, and in vitro reconstitution biochemistry. We found that the BAP1-ASXL2 interaction is direct and high affinity, occurring through the ASXH domain of ASXL2, an obligate partner for BAP1 enzymatic activity. The ASXH domain was the minimal domain for binding the BAP1 ULD domain, and mutations on the surfaces of predicted helices of ASXH abolished BAP1 association and stimulation of BAP1 enzymatic activity. The BAP1-UCH, BAP1-ULD, and ASXH domains formed a cooperative stable ternary complex required for deubiquitination. We defined four classes of alterations in BAP1 outside the UCH domain, each failing to productively recruit ASXH to the wild-type BAP1 catalytic site via the ULD, resulting in loss of BAP1 ubiquitin hydrolase activity. Our results indicate that many BAP1 mutations act allosterically to inhibit ASXH binding, thereby leading to loss of enzyme activity. Small molecule approaches to reactivate latent wild-type UCH activity of these mutants might be therapeutically viable.
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BAP1 is a bona fide tumor suppressor genetic evidence from mouse models carrying heterozygous germline BAP1 mutations
Cancer Research, 2016Co-Authors: Yuwaraj Kadariya, Mitchell Cheung, Frank J Rauscher, Jinfei Xu, Eleonora Sementino, Craig W Menges, Andres J P Kleinszanto, Joseph R TestaAbstract:Individuals harboring inherited heterozygous germline mutations in BAP1 are predisposed to a range of benign and malignant tumor types, including malignant mesothelioma, melanoma, and kidney carcinoma. However, evidence to support a tumor suppressive role for BAP1 in cancer remains contradictory. To test experimentally whether BAP1 behaves as a tumor suppressor, we monitored spontaneous tumor development in three different mouse models with germline heterozygous mutations in BAP1, including two models in which the knock-in mutations are identical to those reported in human BAP1 cancer syndrome families. We observed spontaneous malignant tumors in 54 of 93 BAP1-mutant mice (58%) versus 4 of 43 (9%) wild-type littermates. All three BAP1-mutant models exhibited a high incidence and similar spectrum of neoplasms, including ovarian sex cord stromal tumors, lung and mammary carcinomas, and spindle cell tumors. Notably, we also observed malignant mesotheliomas in two BAP1-mutant mice, but not in any wild-type animals. We further confirmed that the remaining wild-type BAP1 allele was lost in both spontaneous ovarian tumors and mesotheliomas, resulting in the loss of BAP1 expression. Additional studies revealed that asbestos exposure induced a highly significant increase in the incidence of aggressive mesotheliomas in the two mouse models carrying clinically relevant BAP1 mutations compared with asbestos-exposed wild-type littermates. Collectively, these findings provide genetic evidence that BAP1 is a bona fide tumor suppressor gene, and offer key insights into the contribution of carcinogen exposure to enhanced cancer susceptibility.
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germline BAP1 mutational landscape of asbestos exposed malignant mesothelioma patients with family history of cancer
Cancer Research, 2016Co-Authors: Jill A Ohar, Hongzhuang Peng, Mitchell Cheung, Frank J Rauscher, Jacqueline Talarchek, Suzanne E Howard, Timothy D Howard, Mary Hesdorffer, Joseph R TestaAbstract:Heritable mutations in the BAP1 tumor suppressor gene predispose individuals to mesothelioma and other cancers. However, a large-scale assessment of germline BAP1 mutation incidence and associated clinical features in mesothelioma patients with a family history of cancer has not been reported. Therefore, we examined the germline BAP1 mutation status of 150 mesothelioma patients with a family history of cancer, 50 asbestos-exposed control individuals with a family history of cancers other than mesothelioma, and 153 asbestos-exposed individuals without familial cancer. No BAP1 alterations were found in control cohorts, but were identified in nine of 150 mesothelioma cases (6%) with a family history of cancer. Alterations among these cases were characterized by both missense and frameshift mutations, and enzymatic activity of BAP1 missense mutants was decreased compared with wild-type BAP1. Furthermore, BAP1 mutation carriers developed mesothelioma at an earlier age that was more often peritoneal than pleural (five of nine) and exhibited improved long-term survival compared to mesothelioma patients without BAP1 mutations. Moreover, many tumors harboring BAP1 germline mutations were associated with BAP1 syndrome, including mesothelioma and ocular/cutaneous melanomas, as well as renal, breast, lung, gastric, and basal cell carcinomas. Collectively, these findings suggest that mesothelioma patients presenting with a family history of cancer should be considered for BAP1 genetic testing to identify those individuals who might benefit from further screening and routine monitoring for the purpose of early detection and intervention. Cancer Res; 76(2); 206–15. ©2015 AACR .
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germline mutation of BAP1 accelerates development of asbestos induced malignant mesothelioma
Cancer Research, 2014Co-Authors: Jinfei Xu, Hongzhuang Peng, Jayashree Karar, Mitchell Cheung, Yuwaraj Kadariya, Jacqueline Talarchek, Eleonora Sementino, Craig W Menges, Samuel Litwin, Frank J RauscherAbstract:Malignant mesotheliomas are highly aggressive tumors usually caused by exposure to asbestos. Germline-inactivating mutations of BAP1 predispose to mesothelioma and certain other cancers. However, why mesothelioma is the predominate malignancy in some BAP1 families and not others, and whether exposure to asbestos is required for development of mesothelioma in BAP1 mutation carriers are not known. To address these questions experimentally, we generated a BAP1 +/− knockout mouse model to assess its susceptibility to mesothelioma upon chronic exposure to asbestos. BAP1 +/− mice exhibited a significantly higher incidence of asbestos-induced mesothelioma than wild-type (WT) littermates (73% vs. 32%, respectively). Furthermore, mesotheliomas arose at an accelerated rate in BAP1 +/− mice than in WT animals (median survival, 43 weeks vs. 55 weeks after initial exposure, respectively) and showed increased invasiveness and proliferation. No spontaneous mesotheliomas were seen in unexposed BAP1 +/− mice followed for up to 87 weeks of age. Mesothelioma cells from BAP1 +/− mice showed biallelic inactivation of BAP1 , consistent with its proposed role as a recessive cancer susceptibility gene. Unlike in WT mice, mesotheliomas from BAP1 +/− mice did not require homozygous loss of Cdkn2a . However, normal mesothelial cells and mesothelioma cells from BAP1 +/− mice showed downregulation of Rb through a p16(Ink4a)-independent mechanism, suggesting that predisposition of BAP1 +/− mice to mesothelioma may be facilitated, in part, by cooperation between BAP1 and Rb. Drawing parallels to human disease, these unbiased genetic findings indicate that BAP1 mutation carriers are predisposed to the tumorigenic effects of asbestos and suggest that high penetrance of mesothelioma requires such environmental exposure. Cancer Res; 74(16); 4388–97. ©2014 AACR .
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the ubiquitin carboxyl hydrolase BAP1 forms a ternary complex with yy1 and hcf 1 and is a critical regulator of gene expression
Molecular and Cellular Biology, 2010Co-Authors: Helen Yu, Frank J Rauscher, Salima Daou, Ian Hammondmartel, Nazar Mashtalir, Julie Ross, Gerald W Hart, Elliot Drobetsky, Eric Milot, El Bachir AffarAbstract:The candidate tumor suppressor BAP1 is a deubiquitinating enzyme (DUB) involved in the regulation of cell proliferation, although the molecular mechanisms governing its function remain poorly defined. BAP1 was recently shown to interact with and deubiquitinate the transcriptional regulator host cell factor 1 (HCF-1). Here we show that BAP1 assembles multiprotein complexes containing numerous transcription factors and cofactors, including HCF-1 and the transcription factor Yin Yang 1 (YY1). Through its coiled-coil motif, BAP1 directly interacts with the zinc fingers of YY1. Moreover, HCF-1 interacts with the middle region of YY1 encompassing the glycine-lysine-rich domain and is essential for the formation of a ternary complex with YY1 and BAP1 in vivo. BAP1 activates transcription in an enzymatic-activity-dependent manner and regulates the expression of a variety of genes involved in numerous cellular processes. We further show that BAP1 and HCF-1 are recruited by YY1 to the promoter of the cox7c gene, which encodes a mitochondrial protein used here as a model of BAP1-activated gene expression. Our findings (i) establish a direct link between BAP1 and the transcriptional control of genes regulating cell growth and proliferation and (ii) shed light on a novel mechanism of transcription regulation involving ubiquitin signaling.
