A tumor suppressor role of the Bub3 spindle checkpoint protein after apoptosis inhibition

Most solid tumors contain aneuploid cells, indicating that the mitotic checkpoint is permissive to the proliferation of chromosomally aberrant cells. However, mutated or altered expression of mitotic checkpoint genes accounts for a minor proportion of human tumors. We describe a Drosophila melanogaster tumorigenesis model derived from knocking down spindle assembly checkpoint (SAC) genes and preventing apoptosis in wing imaginal discs. Bub3-deficient tumors that were also deficient in apoptosis displayed neoplastic growth, chromosomal aneuploidy, and high proliferative potential after transplantation into adult flies. Inducing aneuploidy by knocking down CENP-E and preventing apoptosis does not induce tumorigenesis, indicating that aneuploidy is not sufficient for hyperplasia. In this system, the aneuploidy caused by a deficient SAC is not driving tumorigenesis because preventing Bub3 from binding to the kinetochore does not cause hyperproliferation. Our data suggest that Bub3 has a nonkinetochore-dependent function that is consistent with its role as a tumor suppressor.

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Kinome-Wide shRNA Screen Reveals Functional Connections Between FANCA, Mitotic Centrosomes and the Spindle Assembly Checkpoint Tumor Suppressor Pathways

Blood ◽

10.1182/blood.v126.23.3612.3612 ◽

2015 ◽

Vol 126 (23) ◽

pp. 3612-3612

Author(s):

Richa Sharma ◽

Zahi Abdul Sater ◽

Rikki Enzor ◽

Ying He ◽

Grzegorz Nalepa

Keyword(s):

Dna Damage ◽

Tumor Suppressor ◽

Fanconi Anemia ◽

Cross Talk ◽

Spindle Assembly Checkpoint ◽

Spindle Assembly ◽

Mitotic Checkpoint ◽

Synthetic Lethal ◽

Shrna Screen

Abstract Fanconi anemia (FA) is a genetic disorder characterized by progressive bone marrow failure, congenital abnormalities and predilection towards development of hematopoietic malignancies, including acute myeloid leukemia (AML). Congenital biallelic disruption of the FA/BRCA signaling network causes Fanconi anemia and somatic mutations within the same genes are increasingly identified in a variety of malignancies in non-FA individuals, consistent with the critical role of this signaling pathway in FA and in the general population. The FA/BRCA tumor suppressor network orchestrates interphase DNA-damage repair (DDR) and DNA replication to maintain genomic stability. Additionally, we and others have demonstrated that the genome housekeeping function of FA/BRCA signaling extends beyond interphase: loss of FA/BRCA signaling perturbs execution of mitosis, including the spindle assembly checkpoint (SAC), centrosome maintenance, cytokinesis and resolution of anaphase DNA bridges. Interphase errors exacerbate mitotic abnormalities and mitotic failure promotes interphase mutagenesis. Consequently, we had demonstrated that primary FA patients' cells accumulate genomic abnormalities consistent with a dual mechanism of impaired interphase DDR/replication and defective mitosis. Previous detailed studies had elucidated multiple mechanisms of interphase DDR-dependent assembly and activation of the FA complex at DNA damage sites to arrest the cell cycle and repair DNA lesions. However, the signaling cross-talk nodes between the FA and mitotic checkpoint pathways remain to be discovered. In this study, we identified functionally relevant mitotic signaling defects resulting from FANCA deficiency via a synthetic lethal kinome-wide pooled shRNA screen in primary patient-derived FANCA -deficient cells compared to isogenic FANCA -corrected cell line. Bioinformatics analysis of our screen results followed by secondary validation of selected hits with alternative shRNAs and small-molecule inhibitors revealed conserved mitotic signal transduction pathways regulating the SAC and centrosome maintenance. Our super-resolution structured illumination (SR-SIM) microscopy coupled with deconvolution imaging revealed that a fraction of FANCA co-localizes with key SAC kinases at mitotic centrosomes and kinetochores, consistent with the role of FANCA in centrosome maintenance and the SAC. Co-immunoprecipitation assays identified the biochemical interaction between FANCA and an essential SAC kinase whose loss is synthetic lethal with FANCA deficiency, providing first insights into the interactions between FA signaling and the canonical SAC network. Together, our study has unraveled functional and biochemical connections between FANCA and the centrosome/SAC kinases, consistent with the essential role of FANCA in cell division. Our ongoing work is aimed at mechanistically dissecting molecular links between these two key tumor suppressor signaling pathways in more detail. We hypothesize that impaired FANCA/SAC cross-talk may contribute to genomic instability in FA-deficient cells and provide opportunities to selectively kill FANCA-/- cells. Disclosures No relevant conflicts of interest to declare.

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Saccharomyces cerevisiae Checkpoint Genes MEC1, RAD17 and RAD24 Are Required for Normal Meiotic Recombination Partner Choice

Genetics ◽

10.1093/genetics/153.2.607 ◽

1999 ◽

Vol 153 (2) ◽

pp. 607-620 ◽

Cited By ~ 4

Author(s):

Jeremy M Grushcow ◽

Teresa M Holzen ◽

Ken J Park ◽

Ted Weinert ◽

Michael Lichten ◽

...

Keyword(s):

Meiotic Recombination ◽

Mitotic Checkpoint ◽

Partner Choice ◽

Wild Type ◽

Spore Viability ◽

Checkpoint Signaling ◽

Ectopic Recombination ◽

Meiotic Progression ◽

Checkpoint Genes

Abstract Checkpoint gene function prevents meiotic progression when recombination is blocked by mutations in the recA homologue DMC1. Bypass of dmc1 arrest by mutation of the DNA damage checkpoint genes MEC1, RAD17, or RAD24 results in a dramatic loss of spore viability, suggesting that these genes play an important role in monitoring the progression of recombination. We show here that the role of mitotic checkpoint genes in meiosis is not limited to maintaining arrest in abnormal meioses; mec1-1, rad24, and rad17 single mutants have additional meiotic defects. All three mutants display Zip1 polycomplexes in two- to threefold more nuclei than observed in wild-type controls, suggesting that synapsis may be aberrant. Additionally, all three mutants exhibit elevated levels of ectopic recombination in a novel physical assay. rad17 mutants also alter the fraction of recombination events that are accompanied by an exchange of flanking markers. Crossovers are associated with up to 90% of recombination events for one pair of alleles in rad17, as compared with 65% in wild type. Meiotic progression is not required to allow ectopic recombination in rad17 mutants, as it still occurs at elevated levels in ndt80 mutants that arrest in prophase regardless of checkpoint signaling. These observations support the suggestion that MEC1, RAD17, and RAD24, in addition to their proposed monitoring function, act to promote normal meiotic recombination.

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Intermediates in the assembly of mitotic checkpoint complexes and their role in the regulation of the anaphase-promoting complex

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1524551113 ◽

2016 ◽

Vol 113 (4) ◽

pp. 966-971 ◽

Cited By ~ 10

Author(s):

Sharon Kaisari ◽

Danielle Sitry-Shevah ◽

Shirly Miniowitz-Shemtov ◽

Avram Hershko

Keyword(s):

Chromosome Segregation ◽

Mitotic Spindle ◽

Spindle Assembly Checkpoint ◽

Mitotic Checkpoint ◽

Anaphase Promoting Complex ◽

Checkpoint Proteins ◽

Sister Chromatids ◽

Unknown Species ◽

Mitotic Checkpoint Complex

The mitotic (or spindle assembly) checkpoint system prevents premature separation of sister chromatids in mitosis and thus ensures the fidelity of chromosome segregation. Kinetochores that are not attached properly to the mitotic spindle produce an inhibitory signal that prevents progression into anaphase. The checkpoint system acts on the Anaphase-Promoting Complex/Cyclosome (APC/C) ubiquitin ligase, which targets for degradation inhibitors of anaphase initiation. APC/C is inhibited by the Mitotic Checkpoint Complex (MCC), which assembles when the checkpoint is activated. MCC is composed of the checkpoint proteins BubR1, Bub3, and Mad2, associated with the APC/C coactivator Cdc20. The intermediary processes in the assembly of MCC are not sufficiently understood. It is also not clear whether or not some subcomplexes of MCC inhibit the APC/C and whether Mad2 is required only for MCC assembly and not for its action on the APC/C. We used purified subcomplexes of mitotic checkpoint proteins to examine these problems. Our results do not support a model in which Mad2 catalytically generates a Mad2-free APC/C inhibitor. We also found that the release of Mad2 from MCC caused a marked (although not complete) decrease in inhibitory action, suggesting a role of Mad2 in MCC for APC/C inhibition. A previously unknown species of MCC, which consists of Mad2, BubR1, and two molecules of Cdc20, contributes to the inhibition of APC/C by the mitotic checkpoint system.

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The role of microRNAs in stemness of cancer stem cells

Oncology Reviews ◽

10.4081/oncol.2013.e8 ◽

2013 ◽

Vol 7 (1) ◽

pp. 8 ◽

Cited By ~ 22

Author(s):

Seyed Mohammad Ali Hosseini Rad ◽

Mahsa Shanaki Bavarsad ◽

Ehsan Arefian ◽

Kaveh Jaseb ◽

Mohammad Shahjahani ◽

...

Keyword(s):

Stem Cells ◽

Tumor Suppressor ◽

Cancer Stem Cells ◽

Signaling Pathways ◽

Embryonic Stem ◽

Recent Theory ◽

Tumor Initiating Cells ◽

Altered Expression ◽

Non Coding Rnas

Cancer is one of the most important diseases of humans, for which no cure has been found so far. Understanding the causes of cancer can pave the way for its treatment. Alteration in genetic elements such as oncogenes and tumor suppressor genes results in cancer. The most recent theory for the origin of cancer has been provided by cancer stem cells (CSCs). Tumor-initiating cells (T-ICs) or CSCs are a small population isolated from tumors and hematologic malignancies. Since CSCs are similar to embryonic stem cells (ESCs) in many aspects (such as pluripotency and self-renewal), recognizing the signaling pathways through which ESCs maintain their stemness can also help identify CSC signaling. One component of these signaling pathways is non-coding RNAs (ncRNAs). ncRNAs are classified in two groups: microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). miRNAs undergo altered expression in cancer. In this regard, they are classified as Onco-miRNAs or tumor suppressor miRNAs. Some miRNAs play similar roles in ESCs and CSCs, such as let-7 and miR-302. This review focuses on the miRNAs involved in stemness of ESCs and CSCs by presenting a summary of the role of miRNAs in other tumor cells.

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AMPK Protects Against Energy Stress and Maintains Histone Acetylation in Leukemia-Initiating-Cell

Blood ◽

10.1182/blood.v128.22.2701.2701 ◽

2016 ◽

Vol 128 (22) ◽

pp. 2701-2701

Author(s):

Yajian Jiang ◽

Daisuke Nakada ◽

Ayumi Kitano ◽

Richard Chapple ◽

Tianyuan Hu ◽

...

Keyword(s):

Tumor Suppressor ◽

Histone Acetylation ◽

Conflicts Of Interest ◽

Causal Link ◽

Energy Deficit ◽

Proliferative Potential ◽

Acetyl Coa ◽

Atp Production ◽

Cell Energy

Abstract Maintaining metabolic homeostasis is a fundamental requirement for cells to survive. One critical requirement is to accomplish a balance between anabolism and catabolism. AMPK regulates this balance by directly sensing AMP-to-ATP ratio and its activation during cell energy deficit promotes ATP production and inhibits ATP usage. Several pieces of evidence point AMPK as a tumor suppressor: the upstream protein, LKB1, is a well-established tumor suppressor; AMPK negatively interacts with the tumor promoting mTOR pathway; anti-diabetic drugs such as metformin with tumor preventive potential are shown to activate AMPK. However, emerging evidence accumulates to support an opposite role of AMPK in promoting tumor growth. AMPK is found to protect tumor cells from metabolic crisis through different mechanisms: autophagy induction; maintaining proper ATP levels and redox environment; histone H2B tail phosphorylation. These two contrasting findings suggested multiple facets of AMPK, thus pointing to the urge to understand mechanisms of AMPK in specific contexts. We examined the role of AMPK by deleting both α1 and α2 subunit in a mouse model of acute myeloid leukemia with t(9;11) translocation. AMPK deficiency depletes the leukemia-initiating-cell population and decreases the leukemogenic potential of these cells. In order to study the metabolic regulatory effects of AMPK, we profiled the metabolites and found AMPK deficiency associates with a decreased level of glycolytic activity and reduction of acetyl-CoA, which is the major donor for histone acetylation. Therefore, we hypothesized that AMPK can affect histone acetylation through regulating the level of acetyl-CoA, and functionally alter leukemogenic potential. We first profiled histone acetylation using western blot with antibodies targeting global histone acetylation and specific histone residues. Intriguingly, we found in AMPK-deficient cells, global histone H3 and H4 acetylation levels are decreased, as well as acetylation at specific histone residues such as H3K9, H3K27 and H4K8. To build a causal link between decreased acetyl-CoA and histone acetylation, we supplemented leukemia-initiating-cells in culture with acetyl-CoA precursors such as acetate and pyruvate. The supplementation successfully increased intracellular acetyl-CoA levels as well as histone acetylation levels. Functionally restoring the intracellular acetyl-CoA and histone acetylation increased the proliferative potential of AMPK-deficient leukemia-initiating-cells and maintained cell at a more undifferentiated state. These results suggest that AMPK regulates a set of leukemogenic genes by maintaining histone acetylation levels. We hypothesize that AMPK links metabolic status to epigenetic gene regulation to promote leukemogenesis. Disclosures No relevant conflicts of interest to declare.

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An α-Tubulin Mutant Demonstrates Distinguishable Functions Among the Spindle Assembly Checkpoint Genes in Saccharomyces cerevisiae

Genetics ◽

10.1093/genetics/161.3.983 ◽

2002 ◽

Vol 161 (3) ◽

pp. 983-994

Author(s):

Katharine C Abruzzi ◽

Margaret Magendantz ◽

Frank Solomon

Keyword(s):

Saccharomyces Cerevisiae ◽

Mutant Allele ◽

Spindle Assembly Checkpoint ◽

Spindle Assembly ◽

Kinase Domain ◽

Mitotic Checkpoint ◽

Cold Sensitivity ◽

Cold Sensitive ◽

Checkpoint Genes

Abstract Cells expressing a mutant allele of α-tubulin, tub1-729, are cold sensitive and arrest as large-budded cells with microtubule defects. The cold sensitivity of tub1-729 is suppressed by extra copies of a subset of the mitotic checkpoint genes BUB1, BUB3, and MPS1, but not MAD1, MAD2, and MAD3. This suppression by checkpoint genes does not depend upon their role in the MAD2-dependent spindle assembly checkpoint. In addition, BUB1 requires an intact kinase domain as well as Bub3p to suppress tub1-729. The data suggest that tub1-729 cells are defective in microtubule-kinetochore attachments and that the products of specific checkpoint genes can act either directly or indirectly to affect these attachments.

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Stochastic effects in a compartmental model for mitotic checkpoint regulation

Journal of Integrative Bioinformatics ◽

10.1515/jib-2007-66 ◽

2007 ◽

Vol 4 (3) ◽

pp. 77-88 ◽

Cited By ~ 13

Author(s):

Bashar Ibrahim ◽

Peter Dittrich ◽

Stephan Diekmann ◽

Eberhard Schmitt

Keyword(s):

Differential Equations ◽

Spindle Assembly Checkpoint ◽

Mitotic Checkpoint ◽

Spindle Pole ◽

Physiological Parameter ◽

Stochastic Effects ◽

Sister Chromatids ◽

Stochastic Term ◽

Parameter Ranges

Summary The proper segregation of sister chromatids at onset of anaphase is surveyed by the mitotic spindle assembly checkpoint. The concentration dynamics of the complexes APC:Cdc20 and MCC:APC determine exit from metaphase to anaphase. We have developed a model based on 14 proteins and complexes to describe concentration dynamics by ordinary differential equations in three compartments coupled by diffusion. One kinetochore in each compartment determines the attachment status to the spindle pole. Here, we focus on the role of noise in the segregation surveillance process. The deterministic differential equations are enriched by a stochastic term adding white noise of different amplitudes. Obviously, for the known physiological parameter ranges, noise does not disturb the checkpoint function. On the other hand, there is a connection between diffusion and noise, that could become important when considering a larger number of chromosomes.

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The role of microRNAs in stemness of cancer stem cells

Oncology Reviews ◽

10.4081/oncol.2013.224 ◽

2013 ◽

pp. e8

Author(s):

Seyed Mohammad Ali Hosseini Rad ◽

Mahsa Shanaki Bavarsad ◽

Ehsan Arefian ◽

Kaveh Jaseb ◽

Mohammad Shahjahani ◽

...

Keyword(s):

Stem Cells ◽

Tumor Suppressor ◽

Cancer Stem Cells ◽

Signaling Pathways ◽

Embryonic Stem ◽

Recent Theory ◽

Tumor Initiating Cells ◽

Altered Expression ◽

Non Coding Rnas

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The Effect of Path Length and Display Size on Memory for Spatial Information

Experimental Psychology (formerly Zeitschrift für Experimentelle Psychologie) ◽

10.1027/1618-3169/a000137 ◽

2012 ◽

Vol 59 (3) ◽

pp. 147-152 ◽

Cited By ~ 11

Author(s):

Katherine Guérard ◽

Sébastien Tremblay

Keyword(s):

Path Length ◽

Potential Role ◽

Spatial Information ◽

Recall Performance ◽

Minor Role ◽

Length Effect ◽

Serial Memory ◽

Fixed Reference ◽

A Minor

In serial memory for spatial information, some studies showed that recall performance suffers when the distance between successive locations increases relatively to the size of the display in which they are presented (the path length effect; e.g., Parmentier et al., 2005) but not when distance is increased by enlarging the size of the display (e.g., Smyth & Scholey, 1994). In the present study, we examined the effect of varying the absolute and relative distance between to-be-remembered items on memory for spatial information. We manipulated path length using small (15″) and large (64″) screens within the same design. In two experiments, we showed that distance was disruptive mainly when it is varied relatively to a fixed reference frame, though increasing the size of the display also had a small deleterious effect on recall. The insertion of a retention interval did not influence these effects, suggesting that rehearsal plays a minor role in mediating the effects of distance on serial spatial memory. We discuss the potential role of perceptual organization in light of the pattern of results.

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THE ROLE OF ANTHROPONYMS IN THE SEMANTIC FIELD OF ARTISTIC WORKS

Naukovy Visnyk of South Ukrainian National Pedagogical University named after K D Ushynsky Linguistic Sciences ◽

10.24195/2616-5317-2019-29-6 ◽

2019 ◽

Vol 2019 (29) ◽

pp. 66-77

Author(s):

Lidiya Derbenyova

Keyword(s):

Literary Work ◽

Main Theme ◽

Semantic Field ◽

New Meanings ◽

Minor Part ◽

The One ◽

A Minor ◽

And Storage ◽

Horizon Of Expectations

The article explores the role of antropoetonyms in the reader’s “horizon of expectation” formation. As a kind of “text in the text”, antropoetonyms are concentrating a large amount of information on a minor part of the text, reflecting the main theme of the work. As a “text” this class of poetonyms performs a number of functions: transmission and storage of information, generation of new meanings, the function of “cultural memory”, which explains the readers’ “horizon of expectations”. In analyzing the context of the literary work we should consider the function of antropoetonyms in vertical context (the link between artistic and other texts, and the groundwork system of culture), as well as in the context of the horizontal one (times’ connection realized in the communication chain from the word to the text; the author’s intention). In this aspect, the role of antropoetonyms in the structure of the literary text is extremely significant because antropoetonyms convey an associative nature, generating a complex mechanism of allusions. It’s an open fact that they always transmit information about the preceding text and suggest a double decoding. On the one hand, the recipient decodes this information, on the other – accepts this as a sort of hidden, “secret” sense.

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