Cancer-Associated Mutations in the MDM2 Zinc Finger Domain Disrupt Ribosomal Protein Interaction and Attenuate MDM2-Induced p53 Degradation

ABSTRACT The p53-inhibitory function of the oncoprotein MDM2 is regulated by a number of MDM2-binding proteins, including ARF and ribosomal proteins L5, L11, and L23, which bind the central acidic domain of MDM2 and inhibit its E3 ubiquitin ligase activity. Various human cancer-associated MDM2 alterations targeting the central acidic domain have been reported, yet the functional significance of these mutations in tumor development has remained unclear. Here, we show that cancer-associated missense mutations targeting MDM2's central zinc finger disrupt the interaction of MDM2 with L5 and L11. We found that the zinc finger mutant MDM2 is impaired in undergoing nuclear export and proteasomal degradation as well as in promoting p53 degradation, yet retains the function of suppressing p53 transcriptional activity. Unlike the wild-type MDM2, whose p53-suppressive activity can be inhibited by L11, the MDM2 zinc finger mutant escapes L11 inhibition. Hence, the MDM2 central zinc finger plays a critical role in mediating MDM2's interaction with ribosomal proteins and its ability to degrade p53, and these roles are disrupted by human cancer-associated MDM2 mutations.

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AKT1-CREB stimulation of PDGFRα expression is pivotal for PTEN deficient tumor development

Cell Death and Disease ◽

10.1038/s41419-021-03433-0 ◽

2021 ◽

Vol 12 (2) ◽

Author(s):

Xiaofeng Wan ◽

Meng Zhou ◽

Fuqiang Huang ◽

Na Zhao ◽

Xu Chen ◽

...

Keyword(s):

Signaling Pathway ◽

Human Cancer ◽

Critical Role ◽

Tumor Development ◽

Growth Factor Receptor ◽

Conditional Knockout ◽

Loss Of Function ◽

Akt Inhibitor ◽

Human Cancer Cell Lines ◽

Direct Binding

AbstractAs evidenced by the behavior of loss-of-function mutants of PTEN in the context of a gain-of-function mutation of AKT1, the PTEN-AKT1 signaling pathway plays a critical role in human cancers. In this study, we demonstrated that a deficiency in PTEN or activation of AKT1 potentiated the expression of platelet-derived growth factor receptor α (PDGFRα) based on studies on Pten−/− mouse embryonic fibroblasts, human cancer cell lines, the hepatic tissues of Pten conditional knockout mice, and human cancer tissues. Loss of PTEN enhanced PDGFRα expression via activation of the AKT1-CREB signaling cascade. CREB transactivated PDGFRα expression by direct binding of the promoter of the PDGFRα gene. Depletion of PDGFRα attenuated the tumorigenicity of Pten-null cells in nude mice. Moreover, the PI3K-AKT signaling pathway has been shown to positively correlate with PDGFRα expression in multiple cancers. Augmented PDGFRα was associated with poor survival of cancer patients. Lastly, combination treatment with the AKT inhibitor MK-2206 and the PDGFR inhibitor CP-673451 displayed synergistic anti-tumor effects. Therefore, activation of the AKT1-CREB-PDGFRα signaling pathway contributes to the tumor growth induced by PTEN deficiency and should be targeted for cancer treatment.

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SPIN1 promotes tumorigenesis by blocking the uL18 (universal large ribosomal subunit protein 18)-MDM2-p53 pathway in human cancer

eLife ◽

10.7554/elife.31275 ◽

2018 ◽

Vol 7 ◽

Cited By ~ 15

Author(s):

Ziling Fang ◽

Bo Cao ◽

Jun-Ming Liao ◽

Jun Deng ◽

Kevin D Plummer ◽

...

Keyword(s):

Ribosomal Proteins ◽

Human Cancer ◽

Ribosomal Subunit ◽

P53 Pathway ◽

Genomic Databases ◽

Human Cancer Cells ◽

Ubiquitin Ligase Activity ◽

Ribosomal Subunit Protein ◽

P53 Activation ◽

P53 Inactivation

Ribosomal proteins (RPs) play important roles in modulating the MDM2-p53 pathway. However, less is known about the upstream regulators of the RPs. Here, we identify SPIN1 (Spindlin 1) as a novel binding partner of human RPL5/uL18 that is important for this pathway. SPIN1 ablation activates p53, suppresses cell growth, reduces clonogenic ability, and induces apoptosis of human cancer cells. Mechanistically, SPIN1 sequesters uL18 in the nucleolus, preventing it from interacting with MDM2, and thereby alleviating uL18-mediated inhibition of MDM2 ubiquitin ligase activity toward p53. SPIN1 deficiency increases ribosome-free uL18 and uL5 (human RPL11), which are required for SPIN1 depletion-induced p53 activation. Analysis of cancer genomic databases suggests that SPIN1 is highly expressed in several human cancers, and its overexpression is positively correlated with poor prognosis in cancer patients. Altogether, our findings reveal that the oncogenic property of SPIN1 may be attributed to its negative regulation of uL18, leading to p53 inactivation.

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Loss of nuclear UBE3A activity is the predominant cause of Angelman syndrome in individuals carrying UBE3A missense mutations

Human Molecular Genetics ◽

10.1093/hmg/ddab050 ◽

2021 ◽

Author(s):

Stijn N V Bossuyt ◽

A Mattijs Punt ◽

Ilona J de Graaf ◽

Janny van den Burg ◽

Mark G Williams ◽

...

Keyword(s):

Catalytic Activity ◽

Angelman Syndrome ◽

Neurodevelopmental Disorder ◽

Critical Role ◽

Rapid Assessment ◽

Missense Mutations ◽

Catalytic Potential ◽

Ubiquitin Ligase Activity ◽

Ube3a Gene

Abstract Angelman syndrome (AS) is a severe neurodevelopmental disorder caused by deletion (~75%) or mutation (~10%) of the UBE3A gene, which encodes a HECT type E3 ubiquitin protein ligase. Although the critical substrates of UBE3A are unknown, previous studies have suggested a critical role of nuclear UBE3A in AS pathophysiology. Here we investigated to what extent UBE3A missense mutations disrupt UBE3A subcellular localization as well as catalytic activity, stability and protein folding. Our functional screen of 31 UBE3A missense mutants revealed that UBE3A mislocalization is the predominant cause of UBE3A dysfunction, accounting for 55% of the UBE3A mutations tested. The second major cause (29%) is a loss of E3-ubiquitin ligase activity, as assessed in an E. coli in vivo ubiquitination assay. Mutations affecting catalytic activity are found not only in the catalytic HECT domain, but also in the N-terminal half of UBE3A, suggesting an important contribution of this N-terminal region to its catalytic potential. Together, our results show that loss of nuclear UBE3A E3 ligase activity is the predominant cause of UBE3A-linked Angelman syndrome. Moreover, our functional analysis screen allows rapid assessment of the pathogenicity of novel UBE3A missense variants which will be of particular importance when treatments for AS become available.

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Critical Contribution of the MDM2 Acidic Domain to p53 Ubiquitination

Molecular and Cellular Biology ◽

10.1128/mcb.23.14.4939-4947.2003 ◽

2003 ◽

Vol 23 (14) ◽

pp. 4939-4947 ◽

Cited By ~ 83

Author(s):

Hidehiko Kawai ◽

Dmitri Wiederschain ◽

Zhi-Min Yuan

Keyword(s):

Nuclear Export ◽

Critical Role ◽

Ring Finger ◽

E3 Ligase ◽

Chimeric Protein ◽

Chimeric Proteins ◽

Ring Finger Domain ◽

Acidic Domain ◽

Ubiquitin E3 Ligase

ABSTRACT MDM2 is an E3 ubiquitin ligase that targets p53 for proteasomal degradation. Recent studies have shown, however, that the ring-finger domain (RFD) of MDM2, where the ubiquitin E3 ligase activity resides, is necessary but not sufficient for p53 ubiquitination, suggesting that an additional activity of MDM2 might be required. To test this possibility, we generated a series of MDM2/MDMX chimeric proteins to assess the contribution of each domain of MDM2 to the ubiquitination process. MDMX is a close structural homolog of MDM2 that nevertheless lacks the E3 ligase activity in vivo. We demonstrate here that MDMX gains self-ubiquitination activity and becomes extremely unstable upon introduction of the MDM2 RFD, indicating that the RFD is essential for self-ubiquitination. This MDMX chimeric protein, however, is unable to ubiquitinate p53 in vivo despite its E3 ligase activity and binding to p53, separating the self-ubiquitination activity of MDM2 from its ability to ubiquitinate p53. Significantly, fusion of the central acidic domain (AD) of MDM2 to the MDMX chimeric protein renders the protein fully capable of ubiquitinating p53, and p53 ubiquitination is associated with p53 degradation and nuclear export. Moreover, the AD mini protein expressed in trans can functionally rescue the AD-lacking MDM2 mutant, further supporting a critical role for the AD in MDM2-mediated p53 ubiquitination.

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Aurora Borealis (Bora), Which Promotes Plk1 Activation by Aurora A, Has an Oncogenic Role in Ovarian Cancer

Cancers ◽

10.3390/cancers12040886 ◽

2020 ◽

Vol 12 (4) ◽

pp. 886 ◽

Cited By ~ 1

Author(s):

Alfonso Parrilla ◽

Marta Barber ◽

Blanca Majem ◽

Josep Castellví ◽

Juan Morote ◽

...

Keyword(s):

Ovarian Cancer ◽

Ex Vivo ◽

Human Cancer ◽

Critical Role ◽

Tumor Development ◽

Loss Of Function ◽

Aurora Borealis ◽

Mitotic Kinase ◽

Cancer Management

Identifying novel actionable factors that critically contribute to tumorigenesis is essential in ovarian cancer, an aggressive and disseminative tumor, with limited therapeutic options available. Here we show that Aurora Borealis (BORA), a mitotic protein that plays a key role in activating the master mitotic kinase polo-like kinase 1 (PLK1), has an oncogenic role in ovarian cancer. Gain and loss of function assays on mouse models and ex vivo patient-derived ascites cultures revealed an oncogenic role of BORA in tumor development and a transcriptome-analysis in clinically representative models depicted BORA’s role in survival, dissemination and inflammatory cancer related-pathways. Importantly, combinatory treatments of FDA-approved inhibitors against oncogenic downstream effectors of BORA displayed synergistic effect in ovarian cancer models, offering promising therapeutic value. Altogether, our findings uncovered for the first time a critical role of BORA in the viability of human cancer cells providing potential novel therapeutic opportunities for ovarian cancer management.

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Involvement of Crm1 in Hepatitis B Virus X Protein-Induced Aberrant Centriole Replication and Abnormal Mitotic Spindles

Molecular and Cellular Biology ◽

10.1128/mcb.23.15.5282-5292.2003 ◽

2003 ◽

Vol 23 (15) ◽

pp. 5282-5292 ◽

Cited By ~ 101

Author(s):

Marshonna Forgues ◽

Michael J. Difilippantonio ◽

Steven P. Linke ◽

Thomas Ried ◽

Kunio Nagashima ◽

...

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

Nuclear Export ◽

Human Cancer ◽

Critical Role ◽

Specific Inhibitor ◽

Mitotic Spindles ◽

Human Cancer Cells ◽

B Virus ◽

Nuclear Export Receptor

ABSTRACT Hepatitis B virus (HBV) includes an X gene (HBx gene) that plays a critical role in liver carcinogenesis. Because centrosome abnormalities are associated with genomic instability in most human cancer cells, we examined the effect of HBx on centrosomes. We found that HBx induced supernumerary centrosomes and multipolar spindles. This effect was independent of mutations in the p21 gene. Furthermore, the ability of HBV to induce supernumerary centrosomes was dependent on the presence of physiological HBx expression. We recently showed that HBx induces cytoplasmic sequestration of Crm1, a nuclear export receptor that binds to Ran GTPase, thereby inducing nuclear localization of NF-κB. Consistently, supernumerary centrosomes were observed in cells treated with a Crm1-specific inhibitor but not with an HBx mutant that lacked the ability to sequester Crm1 in the cytoplasm. Moreover, a fraction of Crm1 was found to be localized at the centrosomes. Immunocytochemical and ultrastructural examination of these supernumerary centrosomes revealed that inactivation of Crm1 was associated with abnormal centrioles. The presence of more than two centrosomes led to an increased frequency of defective mitoses and chromosome transmission errors. Based on this evidence, we suggest that Crm1 is actively involved in maintaining centrosome integrity and that HBx disrupts this process by inactivating Crm1 and thus contributes to HBV-mediated carcinogenesis.

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Upregulation of 5′-terminal oligopyrimidine mRNA translation upon loss of the ARF tumor suppressor

Scientific Reports ◽

10.1038/s41598-020-79379-8 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Kyle A. Cottrell ◽

Ryan C. Chiou ◽

Jason D. Weber

Keyword(s):

Protein Synthesis ◽

Tumor Cells ◽

Ribosomal Proteins ◽

Human Cancer ◽

Mrna Translation ◽

Ribosome Profiling ◽

Translational Efficiency ◽

Gene Encoding ◽

Terminal Oligopyrimidine ◽

Ribosome Export

AbstractTumor cells require nominal increases in protein synthesis in order to maintain high proliferation rates. As such, tumor cells must acquire enhanced ribosome production. How the numerous mutations in tumor cells ultimately achieve this aberrant production is largely unknown. The gene encoding ARF is the most commonly deleted gene in human cancer. ARF plays a significant role in regulating ribosomal RNA synthesis and processing, ribosome export into the cytoplasm, and global protein synthesis. Utilizing ribosome profiling, we show that ARF is a major suppressor of 5′-terminal oligopyrimidine mRNA translation. Genes with increased translational efficiency following loss of ARF include many ribosomal proteins and translation factors. Knockout of p53 largely phenocopies ARF loss, with increased protein synthesis and expression of 5′-TOP encoded proteins. The 5′-TOP regulators eIF4G1 and LARP1 are upregulated in Arf- and p53-null cells.

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The transcription factor SlHY5 regulates the ripening of tomato fruit at both the transcriptional and translational levels

Horticulture Research ◽

10.1038/s41438-021-00523-0 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Weihao Wang ◽

Peiwen Wang ◽

Xiaojing Li ◽

Yuying Wang ◽

Shiping Tian ◽

...

Keyword(s):

Fruit Ripening ◽

Nutritional Quality ◽

Ribosomal Proteins ◽

Anthocyanin Biosynthesis ◽

Tomato Fruit ◽

Critical Role ◽

Regulation Of Gene Expression ◽

Protein Translation ◽

Transcriptional Level ◽

Translation Efficiency

AbstractLight plays a critical role in plant growth and development, but the mechanisms through which light regulates fruit ripening and nutritional quality in horticultural crops remain largely unknown. Here, we found that ELONGATED HYPOCOTYL 5 (HY5), a master regulator in the light signaling pathway, is required for normal fruit ripening in tomato (Solanum lycopersicum). Loss of function of tomato HY5 (SlHY5) impairs pigment accumulation and ethylene biosynthesis. Transcriptome profiling identified 2948 differentially expressed genes, which included 1424 downregulated and 1524 upregulated genes, in the Slhy5 mutants. In addition, genes involved in carotenoid and anthocyanin biosynthesis and ethylene signaling were revealed as direct targets of SlHY5 by chromatin immunoprecipitation. Surprisingly, the expression of a large proportion of genes encoding ribosomal proteins was downregulated in the Slhy5 mutants, and this downregulation pattern was accompanied by a decrease in the abundance of ribosomal proteins. Further analysis demonstrated that SlHY5 affected the translation efficiency of numerous ripening-related genes. These data indicate that SlHY5 regulates fruit ripening both at the transcriptional level by targeting specific molecular pathways and at the translational level by affecting the protein translation machinery. Our findings unravel the regulatory mechanisms of SlHY5 in controlling fruit ripening and nutritional quality and uncover the multifaceted regulation of gene expression by transcription factors.

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Interleukin-11-expressing fibroblasts have a unique gene signature correlated with poor prognosis of colorectal cancer

Nature Communications ◽

10.1038/s41467-021-22450-3 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Takashi Nishina ◽

Yutaka Deguchi ◽

Daisuke Ohshima ◽

Wakami Takeda ◽

Masato Ohtsuka ◽

...

Keyword(s):

Colorectal Cancer ◽

Tumor Cells ◽

Human Cancer ◽

Tumor Development ◽

Gene Signature ◽

Free Survival ◽

Expression Of Genes ◽

Reporter Mice ◽

Interleukin 11

AbstractInterleukin (IL)-11 is a member of the IL-6 family of cytokines and is involved in multiple cellular responses, including tumor development. However, the origin and functions of IL-11-producing (IL-11+) cells are not fully understood. To characterize IL-11+ cells in vivo, we generate Il11 reporter mice. IL-11+ cells appear in the colon in murine tumor and acute colitis models. Il11ra1 or Il11 deletion attenuates the development of colitis-associated colorectal cancer. IL-11+ cells express fibroblast markers and genes associated with cell proliferation and tissue repair. IL-11 induces the activation of colonic fibroblasts and epithelial cells through phosphorylation of STAT3. Human cancer database analysis reveals that the expression of genes enriched in IL-11+ fibroblasts is elevated in human colorectal cancer and correlated with reduced recurrence-free survival. IL-11+ fibroblasts activate both tumor cells and fibroblasts via secretion of IL-11, thereby constituting a feed-forward loop between tumor cells and fibroblasts in the tumor microenvironment.

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Deciphering the Mounting Complexity of the p53 Regulatory Network in Correlation to Long Non-Coding RNAs (lncRNAs) in Ovarian Cancer

Cells ◽

10.3390/cells9030527 ◽

2020 ◽

Vol 9 (3) ◽

pp. 527 ◽

Cited By ~ 10

Author(s):

Sonali Pal ◽

Manoj Garg ◽

Amit Kumar Pandey

Keyword(s):

Ovarian Cancer ◽

Molecular Mechanisms ◽

Human Cancer ◽

Critical Role ◽

Functional Characterization ◽

Great Promise ◽

Altered Expression ◽

Disease Biology ◽

Non Coding Rnas ◽

Post Transcriptional Regulation

Amongst the various gynecological malignancies affecting female health globally, ovarian cancer is one of the predominant and lethal among all. The identification and functional characterization of long non-coding RNAs (lncRNAs) are made possible with the advent of RNA-seq and the advancement of computational logarithm in understanding human disease biology. LncRNAs can interact with deoxyribonucleic acid (DNA), ribonucleic acid (RNA), proteins and their combinations. Moreover, lncRNAs regulate orchestra of diverse functions including chromatin organization and transcriptional and post-transcriptional regulation. LncRNAs have conferred their critical role in key biological processes in human cancer including tumor initiation, proliferation, cell cycle, apoptosis, necroptosis, autophagy, and metastasis. The interwoven function of tumor-suppressor protein p53-linked lncRNAs in the ovarian cancer paradigm is of paramount importance. Several lncRNAs operate as p53 regulators or effectors and modulates a diverse array of functions either by participating in various signaling cascades or via interaction with different proteins. This review highlights the recent progress made in the identification of p53 associated lncRNAs while elucidating their molecular mechanisms behind the altered expression in ovarian cancer tumorigenesis. Moreover, the development of novel clinical and therapeutic strategies for targeting lncRNAs in human cancers harbors great promise.

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