scholarly journals Interferon-Inducible Protein IFIXα1 Functions as a Negative Regulator of HDM2

2006 ◽  
Vol 26 (5) ◽  
pp. 1979-1996 ◽  
Author(s):  
Yi Ding ◽  
Jin-Fong Lee ◽  
Hua Lu ◽  
Mong-Hong Lee ◽  
Duen-Hwa Yan
Keyword(s):  
Amino Acid ◽  
Gene Family ◽  
Tumor Suppression ◽  
P53 Protein ◽  
Negative Regulator ◽  
Breast Cancer Cell Lines ◽  
Homologous Proteins ◽  
Protein Levels ◽  
P53 Activation ◽  
Inducible Protein

ABSTRACT The 200-amino-acid repeat (HIN-200) gene family with the hematopoietic interferon (IFN)-inducible nuclear protein encodes highly homologous proteins involved in cell growth, differentiation, autoimmunity, and tumor suppression. IFIX is the newest member of the human HIN-200 family and is often downregulated in breast tumors and breast cancer cell lines. The expression of the longest isoform of IFIX gene products, IFIXα1, is associated with growth inhibition, suppression of transformation, and tumorigenesis. However, the mechanism underlying the tumor suppression activity of IFIXα1 is not well understood. Here, we show that IFIXα1 downregulates HDM2, a principal negative regulator of p53, at the posttranslational level. IFIXα1 destabilizes HDM2 protein and promotes its ubiquitination. The E3 ligase activity of HDM2 appears to be required for this IFIXα1 effect. Importantly, HDM2 downregulation is required for the IFIXα1-mediated increase of p53 protein levels, transcriptional activity, and nuclear localization, suggesting that IFIXα1 positively regulates p53 by acting as a negative regulator of HDM2. We found that IFIXα1 interacts with HDM2. Interestingly, the signature motif of the HIN-200 gene family, i.e., the 200-amino-acid HIN domain of IFIXα1, is sufficient not only for binding HDM2 but also for downregulating it, leading to p53 activation. Finally, we show that IFIX mediates HDM2 downregulation in an IFN-inducible system. Together, these results suggest that IFIXα1 functions as a tumor suppressor by repressing HDM2 function.

scholarly journals MDM2 antagonists induce p53-dependent apoptosis in AML: implications for leukemia therapy

Blood ◽  
2005 ◽  
Vol 106 (9) ◽  
pp. 3150-3159 ◽  
Author(s):  
Kensuke Kojima ◽  
Marina Konopleva ◽  
Ismael J. Samudio ◽  
Masato Shikami ◽  
Maria Cabreira-Hansen ◽  
...  
Keyword(s):  
Progenitor Cells ◽  
Transcriptional Activation ◽  
P53 Protein ◽  
Negative Regulator ◽  
Wild Type ◽  
Protein Levels ◽  
P53 Signaling ◽  
P53 Activation ◽  
Induction Of Apoptosis ◽  
Wild Type P53

AbstractAlthough TP53 mutations are rare in acute myeloid leukemia (AML), inactivation of wild-type p53 protein frequently occurs through overexpression of its negative regulator MDM2 (murine double minute 2). Recently, small-molecule antagonists of MDM2, Nutlins, have been developed that inhibit the p53-MDM2 interaction and activate p53 signaling. Here, we study the effects of p53 activation by Nutlin-3 in AML cells. Treatment with MDM2 inhibitor triggered several molecular events consistent with induction of apoptosis: loss of mitochondrial membrane potential, caspase activation, phosphatidylserine externalization, and DNA fragmentation. There was a positive correlation in primary AML samples with wild-type p53 between baseline MDM2 protein levels and apoptosis induced by MDM2 inhibition. No induction of apoptosis was observed in AML samples harboring mutant p53. Colony formation of AML progenitors was inhibited in a dose-dependent fashion, whereas normal CD34+ progenitor cells were less affected. Mechanistic studies suggested that Nutlin-induced apoptosis was mediated by both transcriptional activation of proapoptotic Bcl-2 family proteins, and transcription-independent mitochondrial permeabilization resulting from mitochondrial p53 translocation. MDM2 inhibition synergistically enhanced cytotoxicity of cytosine arabinoside and doxorubicin in AML blasts but not in normal hematopoietic progenitor cells. p53 activation by targeting the p53-MDM2 interaction might offer a novel therapeutic strategy for AML that retain wild-type p53.

scholarly journals Engineering Optogenetic Control of Endogenous p53 Protein Levels

2019 ◽  
Vol 9 (10) ◽  
pp. 2095 ◽  
Author(s):  
Pierre Wehler ◽  
Barbara Di Ventura
Keyword(s):  
Blue Light ◽  
Light Exposure ◽  
P53 Protein ◽  
P53 Gene ◽  
Protein Levels ◽  
Cycle Arrest ◽  
P53 Activation ◽  
Low Levels ◽  
Export System ◽  
Transcription Factor P53

The transcription factor p53 is a stress sensor that turns specific sets of genes on to allow the cell to respond to the stress depending on its severity and type. p53 is classified as tumor suppressor because its function is to maintain genome integrity promoting cell cycle arrest, apoptosis, or senescence to avoid proliferation of cells with damaged DNA. While in many human cancers the p53 gene is itself mutated, there are some in which the dysfunction of the p53 pathway is caused by the overexpression of negative regulators of p53, such as Mdm2, that keep it at low levels at all times. Here we develop an optogenetic approach to control endogenous p53 levels with blue light. Specifically, we control the nuclear localization of the Mmd2-binding PMI peptide using the light-inducible export system LEXY. In the dark, the PMI-LEXY fusion is nuclear and binds to Mdm2, consenting to p53 to accumulate and transcribe the target gene p21. Blue light exposure leads to the export of the PMI-LEXY fusion into the cytosol, thereby Mdm2 is able to degrade p53 as in the absence of the peptide. This approach may be useful to study the effect of localized p53 activation within a tissue or organ.

scholarly journals The 40bp Indel Polymorphism rs150550023 in the MDM2 Promoter is Associated with Intriguing Shifts in Gene Expression in the p53-MDM2 Regulatory Hub

Cancers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3363
Author(s):  
Heidi Miedl ◽  
Bianca Dietrich ◽  
Klaus Kaserer ◽  
Martin Schreiber
Keyword(s):  
Breast Cancer ◽  
Genetic Risk ◽  
Target Genes ◽  
P53 Protein ◽  
Age At Onset ◽  
Negative Regulator ◽  
Mrna Levels ◽  
Breast Cancer Patients ◽  
Indel Polymorphism ◽  
Protein Levels

Most low-penetrance genetic risk factors for cancer are located in noncoding regions, presumably altering the regulation of neighboring genes. The poorly characterized Indel polymorphism rs150550023 (rs3730485; del1518) in the promoter of MDM2 (human homolog of mouse double minute 2) is a biologically plausible candidate genetic risk factor, which might influence the expression of MDM2, a key negative regulator of the central tumor suppressor p53. Here, we genotyped rs150550023 in a Central European hospital-based case–control study of 407 breast cancer patients and 254 female controls. mRNA levels of MDM2, p53, and the p53 target genes p21, BAX, and PERP were quantified with qRT-PCR, and p53 protein was assessed with immune histochemistry in ≈100 primary breast tumors with ascertained rs150550023 genotype. We found no evidence for an association of rs150550023 with the risk, age at onset, or prognosis of breast cancer. A possible synergism was observed with SNP309 in promoter P2 of MDM2. Mean mRNA levels of MDM2, p53, p21, and BAX were ≈1.5–3 fold elevated in TP53 wildtype tumors with the minor homozygous Del/Del genotype. However, systematic shifts in p53 protein levels or mutation rates were not observed, suggesting that the elevated p53 mRNA levels are due to regulatory feedback loops that compensate for the effects of rs150550023 on MDM2 expression.

scholarly journals p53 dynamics vary between tissues and are linked with radiation sensitivity

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jacob Stewart-Ornstein ◽  
Yoshiko Iwamoto ◽  
Miles A. Miller ◽  
Mark A. Prytyskach ◽  
Stephane Ferretti ◽  
...  
Keyword(s):  
Cultured Cells ◽  
Temporal Dynamics ◽  
P53 Protein ◽  
Radiation Sensitivity ◽  
Negative Regulator ◽  
Normal Tissues ◽  
P53 Signaling ◽  
P53 Activation ◽  
Transcription Factor P53

AbstractRadiation sensitivity varies greatly between tissues. The transcription factor p53 mediates the response to radiation; however, the abundance of p53 protein does not correlate well with the extent of radiosensitivity across tissues. Given recent studies showing that the temporal dynamics of p53 influence the fate of cultured cells in response to irradiation, we set out to determine the dynamic behavior of p53 and its impact on radiation sensitivity in vivo. We find that radiosensitive tissues show prolonged p53 signaling after radiation, while more resistant tissues show transient p53 activation. Sustaining p53 using a small molecule (NMI801) that inhibits Mdm2, a negative regulator of p53, reduced viability in cell culture and suppressed tumor growth. Our work proposes a mechanism for the control of radiation sensitivity and suggests tools to alter the dynamics of p53 to enhance tumor clearance. Similar approaches can be used to enhance killing of cancer cells or reduce toxicity in normal tissues following genotoxic therapies.

scholarly journals TRAIL-receptor 2—a novel negative regulator of p53

2021 ◽  
Vol 12 (8) ◽  
Author(s):  
Anna Willms ◽  
Hella Schupp ◽  
Michelle Poelker ◽  
Alshaimaa Adawy ◽  
Jan Frederik Debus ◽  
...  
Keyword(s):  
Target Genes ◽  
P53 Protein ◽  
Nuclear Bodies ◽  
Negative Regulator ◽  
Trail Receptor ◽  
Wild Type ◽  
Protein Levels ◽  
Pml Nuclear Bodies ◽  
P53 Target Gene

AbstractTNF-related apoptosis-inducing ligand (TRAIL) receptor 2 (TRAIL-R2) can induce apoptosis in cancer cells upon crosslinking by TRAIL. However, TRAIL-R2 is highly expressed by many cancers suggesting pro-tumor functions. Indeed, TRAIL/TRAIL-R2 also activate pro-inflammatory pathways enhancing tumor cell invasion, migration, and proliferation. In addition, nuclear TRAIL-R2 (nTRAIL-R2) promotes malignancy by inhibiting miRNA let-7-maturation. Here, we show that TRAIL-R2 interacts with the tumor suppressor protein p53 in the nucleus, assigning a novel pro-tumor function to TRAIL-R2. Knockdown of TRAIL-R2 in p53 wild-type cells increases the half-life of p53 and the expression of its target genes, whereas its re-expression decreases p53 protein levels. Interestingly, TRAIL-R2 also interacts with promyelocytic leukemia protein (PML), a major regulator of p53 stability. PML-nuclear bodies are also the main sites of TRAIL-R2/p53 co-localization. Notably, knockdown or destruction of PML abolishes the TRAIL-R2-mediated regulation of p53 levels. In summary, our finding that nTRAIL-R2 facilitates p53 degradation and thereby negatively regulates p53 target gene expression provides insight into an oncogenic role of TRAIL-R2 in tumorigenesis that particularly manifests in p53 wild-type tumors.

scholarly journals WIP1 Inhibition by GSK2830371 Potentiates HDM201 through Enhanced p53 Phosphorylation and Activation in Liver Adenocarcinoma Cells

Cancers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 3876
Author(s):  
Chiao-En Wu ◽  
Chen-Yang Huang ◽  
Chiao-Ping Chen ◽  
Yi-Ru Pan ◽  
John Wen-Cheng Chang ◽  
...  
Keyword(s):  
Rna Sequencing ◽  
Primary Liver Cancer ◽  
P53 Protein ◽  
Intrahepatic Bile Duct ◽  
Cell Cycle Distribution ◽  
P53 Signaling ◽  
Adenocarcinoma Cells ◽  
Wip1 Phosphatase ◽  
P53 Activation ◽  
Novel Strategy

Background: Intrahepatic cholangiocarcinoma (iCCA) is an adenocarcinoma arising from the intrahepatic bile duct. It is the second most common primary liver cancer and has a poor prognosis. Activation of p53 by targeting its negative regulators, MDM2 and WIP1, is a potential therapy for wild-type p53 cancers, but few reports for iCCA or liver adenocarcinoma exist. Methods: Both RBE and SK-Hep-1 liver adenocarcinoma cell lines were treated with the HDM201 (Siremadlin) MDM2-p53 binding antagonist alone or in combination with the GSK2830371 WIP1 phosphatase inhibitor. Cell proliferation, clonogenicity, protein and mRNA expression, cell cycle distribution, and RNA sequencing were performed to investigate the effect and mechanism of this combination. Results: GSK2830371 alone demonstrated minimal activity on proliferation and colony formation, but potentiated growth inhibition (two-fold decrease in GI50) and cytotoxicity (four-fold decrease in IC50) by HDM201 on RBE and SK-Hep-1 cells. HDM201 increased p53 protein expression, leading to transactivation of downstream targets (p21 and MDM2). Combination with GSK2830371 increased p53 phosphorylation, resulting in an increase in both p53 accumulation and p53-dependent trans-activation. G2/M arrest was observed by flow cytometry after this treatment combination. RNA sequencing identified 21 significantly up-regulated genes and five downregulated genes following p53 reactivation by HDM201 in combination with GSK2830371 at 6 h and 24 h time points compared with untreated controls. These genes were predominantly known transcriptional targets regulated by the p53 signaling pathway, indicating enhanced p53 activation as the predominant effect of this combination. Conclusion: The current study demonstrated that GSK2830371 enhanced the p53-dependent antiproliferative and cytotoxic effect of HDM201 on RBE and SK-Hep-1 cells, providing a novel strategy for potentiating the efficacy of targeting the p53 pathway in iCCA.

scholarly journals Lentiviral CRISPR-guided RNA library screening identified Adam17 as an upstream negative regulator of Procr in mammary epithelium

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Ting Wu ◽  
Yinghua Wang ◽  
Tianxiong Xiao ◽  
Yirui Ai ◽  
Jinsong Li ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Membrane Proteins ◽  
Epithelial Cells ◽  
Adult Stem Cells ◽  
Vascular System ◽  
Negative Regulator ◽  
Breast Cancer Cell Lines ◽  
Screening System ◽  
Membrane Expression ◽  
Sorting Technique

Abstract Background Protein C receptor (Procr) has recently been shown to mark resident adult stem cells in the mammary gland, vascular system, and pancreatic islets. More so, high Procr expression was also detected and used as indicator for subsets of triple-negative breast cancers (TNBCs). Previous study has revealed Procr as a target of Wnt/β-catenin signaling; however, direct upstream regulatory mechanism of Procr remains unknown. To comprehend the molecular role of Procr during physiology and pathology, elucidating the upstream effectors of Procr is necessary. Here, we provide a system for screening negative regulators of Procr, which could be adapted for broad molecular analysis on membrane proteins. Results We established a screening system which combines CRISPR-Cas9 guided gene disruption with fluorescence activated cell sorting technique (FACS). CommaDβ (murine epithelial cells line) was used for the initial Procr upstream effector screening using lentiviral CRISPR-gRNA library. Shortlisted genes were further validated through individual lentiviral gRNA infection followed by Procr expression evaluation. Adam17 was identified as a specific negative inhibitor of Procr expression. In addition, MDA-MB-231 cells and Hs578T cells (human breast cancer cell lines) were used to verify the conserved regulation of ADAM17 over PROCR expression. Conclusion We established an efficient CRISPR-Cas9/FACS screening system, which identifies the regulators of membrane proteins. Through this system, we identified Adam17 as the negative regulator of Procr membrane expression both in mammary epithelial cells and breast cancer cells.

scholarly journals Bcl-2-dependent autophagy disruption during aging impairs amino acid utilization that is restored by hochuekkito

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Miwa Nahata ◽  
Sachiko Mogami ◽  
Hitomi Sekine ◽  
Seiichi Iizuka ◽  
Naoto Okubo ◽  
...  
Keyword(s):  
Amino Acid ◽  
Energy Homeostasis ◽  
Mitochondrial Dynamics ◽  
Negative Regulator ◽  
Aged Mice ◽  
Glucose Levels ◽  
Therapeutic Benefits ◽  
Age Related ◽  
Daily Food ◽  
Young Mice

AbstractChronic undernutrition contributes to the increase in frailty observed among elderly adults, which is a pressing issue in the sector of health care for older people worldwide. Autophagy, an intracellular recycling system, is closely associated with age-related pathologies. Therefore, decreased autophagy in aging could be involved in the disruption of energy homeostasis that occurs during undernutrition; however, the physiological mechanisms underlying this process remain unknown. Here, we showed that 70% daily food restriction (FR) induced fatal hypoglycemia in 23–26-month-old (aged) mice, which exhibited significantly lower hepatic autophagy than 9-week-old (young) mice. The liver expressions of Bcl-2, an autophagy-negative regulator, and Beclin1–Bcl-2 binding, were increased in aged mice compared with young mice. The autophagy inducer Tat-Beclin1 D11, not the mTOR inhibitor rapamycin, decreased the plasma levels of the glucogenic amino acid and restored the blood glucose levels in aged FR mice. Decreased liver gluconeogenesis, body temperature, physical activity, amino acid metabolism, and hepatic mitochondrial dynamics were observed in the aged FR mice. These changes were restored by treatment with hochuekkito that is a herbal formula containing several autophagy-activating ingredients. Our results indicate that Bcl-2 upregulation in the liver during the aging process disturbs autophagy activation, which increases the vulnerability to undernutrition. The promotion of liver autophagy may offer clinical therapeutic benefits to frail elderly patients.

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