scholarly journals Centromere-associated protein-E is essential for the mammalian mitotic checkpoint to prevent aneuploidy due to single chromosome loss

2003 ◽  
Vol 162 (4) ◽  
pp. 551-563 ◽  
Author(s):  
Beth A.A. Weaver ◽  
Zahid Q. Bonday ◽  
Frances R. Putkey ◽  
Geert J.P.L. Kops ◽  
Alain D. Silk ◽  
...  
Keyword(s):  
Kinase Activity ◽  
Cell Cycle Control ◽  
Mitotic Checkpoint ◽  
Chromosome Loss ◽  
Single Chromosome ◽  
Binding Partner ◽  
Anaphase Onset ◽  
Primary Mouse

Centromere-associated protein-E (CENP-E) is an essential mitotic kinesin that is required for efficient, stable microtubule capture at kinetochores. It also directly binds to BubR1, a kinetochore-associated kinase implicated in the mitotic checkpoint, the major cell cycle control pathway in which unattached kinetochores prevent anaphase onset. Here, we show that single unattached kinetochores depleted of CENP-E cannot block entry into anaphase, resulting in aneuploidy in 25% of divisions in primary mouse fibroblasts in vitro and in 95% of regenerating hepatocytes in vivo. Without CENP-E, diminished levels of BubR1 are recruited to kinetochores and BubR1 kinase activity remains at basal levels. CENP-E binds to and directly stimulates the kinase activity of purified BubR1 in vitro. Thus, CENP-E is required for enhancing recruitment of its binding partner BubR1 to each unattached kinetochore and for stimulating BubR1 kinase activity, implicating it as an essential amplifier of a basal mitotic checkpoint signal.

scholarly journals The ARF tumor suppressor prevents chromosomal instability and ensures mitotic checkpoint fidelity through regulation of Aurora B

2014 ◽  
Vol 25 (18) ◽  
pp. 2761-2773 ◽  
Author(s):  
Eric M.C. Britigan ◽  
Jun Wan ◽  
Lauren M. Zasadil ◽  
Sean D. Ryan ◽  
Beth A. Weaver
Keyword(s):  
Tumor Suppressor ◽  
Mitotic Checkpoint ◽  
Aurora B ◽  
Multipolar Spindles ◽  
Primary Mouse ◽  
The Common ◽  
Additional Tumor ◽  
Cdkn2a Locus

The ARF tumor suppressor is part of the CDKN2A locus and is mutated or undetectable in numerous cancers. The best-characterized role for ARF is in stabilizing p53 in response to cellular stress. However, ARF has tumor suppressive functions outside this pathway that have not been fully defined. Primary mouse embryonic fibroblasts (MEFs) lacking the ARF tumor suppressor contain abnormal numbers of chromosomes. However, no role for ARF in cell division has previously been proposed. Here we demonstrate a novel, p53-independent role for ARF in the mitotic checkpoint. Consistent with this, loss of ARF results in aneuploidy in vitro and in vivo. ARF−/− MEFs exhibit mitotic defects including misaligned and lagging chromosomes, multipolar spindles, and increased tetraploidy. ARF−/− cells exhibit overexpression of Mad2, BubR1, and Aurora B, but only overexpression of Aurora B phenocopies mitotic defects observed in ARF−/− MEFs. Restoring Aurora B to near-normal levels rescues mitotic phenotypes in cells lacking ARF. Our results define an unexpected role for ARF in chromosome segregation and mitotic checkpoint function. They further establish maintenance of chromosomal stability as one of the additional tumor-suppressive functions of ARF and offer a molecular explanation for the common up-regulation of Aurora B in human cancers.

Dissection of Bcr-abl Structural Domains Relating to Kinase Auto-Inhibition Using a Forward Mutational Screen with the Non-ATP Competitive Inhibitor GNF-2.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1021-1021 ◽  
Author(s):  
John T. Powers ◽  
Mohammad Azam ◽  
Nathanael S. Gray ◽  
George Q. Daley
Keyword(s):  
Kinase Activity ◽  
Binding Pocket ◽  
Sh3 Domain ◽  
Binding Domain ◽  
Binding Partner ◽  
Abl Kinase ◽  
Indirect Mechanism ◽  
Resistance Model

Abstract The Bcr-abl kinase is the causative agent for chronic myeloid leukemia (CML) and has been established as the primary clinical target for treatment of the disease through extensive use of Imatinib. Imatinib is the defining member of a class of ATP-binding site competitive inhibitors that lock Bcr-abl in an inactive conformation. Mutational screens of Bcr-abl using Imatinib and its derivatives as probes have been highly informative in prediction of clinically relevant mutations of Bcr-abl as well as in revealing the structure/function relationship of the kinase in general. Using compounds with a distinct mechanism of action from the Imatinib class to interrogate Bcr-abl will contribute to both more complete understanding of kinase function as well as to potential combination therapies for more effective treatment of CML. GNF-2, a recently identified inhibitor of Bcr-abl, establishes a new class of non-ATP competitive Bcr-abl family kinase inhibitors that may be developed as therapeutic agents for CML. GNF-2 effectively impairs the in vivo kinase activity of Bcr-abl and the growth of Bcr-abl transformed cells. GNF-2 functions at least in part through association with the myristate binding pocket of Bcr-abl. In order to further elucidate the mechanism of GNF-2 action as well as clinically relevant GNF-2 resistant mutants of Bcr-abl, a mutational screen coupling Bcr-abl mutagenesis to selection of drug resistance was performed using GNF-2 as probe. A number of functionally distinct resistant Bcr-abl mutations were recovered. Over half of all GNF-2 resistant clones harbored Bcr-abl mutations affecting the myristate binding pocket or the abl-SH3 domain, suggesting two potential methods of mutational resistance. The myristate binding domain mutants support a direct resistance model whereby GNF-2 association with Bcr-abl is impaired by disruption of the myristate binding pocket. Given a previous report that GNF-2 cannot inhibit Bcr-abl kinase activity in vitro, a novel model emerges for indirect resistance to GNF-2 by SH3 mutants that lose affinity for an inhibitory associated protein. The indirect resistance model specifically suggests that GNF-2 association confers a structural state of wildtype Bcr-abl which facilitates association to a putative inhibitory binding partner, thereby affecting inhibition. Indeed, the strongest of several candidate inhibitory binding partners, the Abl-SH3 domain binding inhibitor Abi-2 was observed to co-immunoprecipitate with Bcr-abl in the presence of GNF-2. This association correlated with reduced Bcr-abl auto-phosphorylation levels. These observations provide preliminary support for an indirect mechanism of Bcr-abl inhibition by GNF-2. Additional experiments involving shRNA knockdown of Abi-2 are being completed to determine the requirement of this Bcr-abl binding partner for GNF-2 activity. Further characterization of the SH3 and myristate binding domain mutants in the context of Abi-2 and GNF-2 binding affinities may establish a previously undescribed indirect mechanism of Bcr-abl inhibition by an allosteric non-ATP inhibitor.

PI3-kinase activity modulates apo B available for hepatic VLDL production in apobec-1−/− mice

2006 ◽  
Vol 291 (3) ◽  
pp. G382-G388 ◽  
Author(s):  
Doru V. Chirieac ◽  
Nicholas O. Davidson ◽  
Charles E. Sparks ◽  
Janet D. Sparks
Keyword(s):  
Insulin Resistance ◽  
Kinase Activity ◽  
Pi3 Kinase ◽  
Apo B ◽  
Glucose Injection ◽  
Primary Mouse ◽  
Mouse Hepatocytes ◽  
Vldl Triglyceride

Insulin regulates hepatic VLDL production by activation of phosphatidylinositide 3-kinase (PI3-kinase) which decreases apo B available for lipid assembly. The current study evaluated the dependence of the VLDL apolipoprotein B (apo B) pathway on PI3-kinase activity in vivo. VLDL production was examined in B100 only, apo B mRNA editing catalytic subunit 1 ( apobec-1 −/−) mice, using the Triton WR 1339 method. Glucose injection suppressed VLDL triglyceride production by 28% in male and by 32% in female mice compared with saline-injected controls. When wortmannin was injected to inhibit PI3-kinase, VLDL triglyceride production was increased by 52% in males and by 89% in females, and VLDL B100 levels paralleled triglyceride changes. Pulse-chase experiments in primary mouse hepatocytes showed that wortmannin increased net freshly synthesized B100 availability by >35%. To test whether physiological insulin resistance produced equivalent effects to wortmannin, we studied male apobec-1 −/− mice who became hyperlipidemic on being fed a fructose-enriched diet. Fructose-fed apobec-1 −/− mice had significantly higher VLDL triglyceride and B100 production rates compared with chow-fed mice, and rates were refractile to glucose or wortmannin. Hepatic VLDL triglyceride and B100 production in wortmannin-injected chow-fed mice equaled that observed in fructose-fed mice. Together, results suggest in vivo and in vitro that wortmannin-sensitive PI3-kinases maintain a basal level of VLDL suppression that is sensitive to changes in activation and that can increase VLDL production when PI3-kinase is inhibited to levels similar to those induced by insulin resistance.

scholarly journals Phosphorylation sites in BubR1 that regulate kinetochore attachment, tension, and mitotic exit

2008 ◽  
Vol 183 (4) ◽  
pp. 667-680 ◽  
Author(s):  
Haomin Huang ◽  
James Hittle ◽  
Francesca Zappacosta ◽  
Roland S. Annan ◽  
Avram Hershko ◽  
...  
Keyword(s):  
Mitotic Checkpoint ◽  
Phosphorylation Sites ◽  
Anaphase Promoting Complex ◽  
Anaphase Onset ◽  
Conserved Residue ◽  
Vitro Data ◽  
In Vitro Data ◽  
Combined Data

BubR1 kinase is essential for the mitotic checkpoint and also for kinetochores to establish microtubule attachments. In this study, we report that BubR1 is phosphorylated in mitosis on four residues that differ from sites recently reported to be phosphorylated by Plk1 (Elowe, S., S. Hummer, A. Uldschmid, X. Li, and E.A. Nigg. 2007. Genes Dev. 21:2205–2219; Matsumura, S., F. Toyoshima, and E. Nishida. 2007. J. Biol. Chem. 282:15217–15227). S670, the most conserved residue, is phosphorylated at kinetochores at the onset of mitosis and dephosphorylated before anaphase onset. Unlike the Plk1-dependent S676 phosphorylation, S670 phosphorylation is sensitive to microtubule attachments but not to kinetochore tension. Functionally, phosphorylation of S670 is essential for error correction and for kinetochores with end-on attachments to establish tension. Furthermore, in vitro data suggest that the phosphorylation status of BubR1 is important for checkpoint inhibition of the anaphase-promoting complex/cyclosome. Finally, RNA interference experiments show that Mps1 is a major but not the exclusive kinase that specifies BubR1 phosphorylation in vivo. The combined data suggest that BubR1 may be an effector of multiple kinases that are involved in discrete aspects of kinetochore attachments and checkpoint regulation.

scholarly journals Involvement of HECTD1 in LPS-induced astrocyte activation via σ-1R-JNK/p38-FOXJ2 axis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ying Tang ◽  
Mengchun Zhou ◽  
Rongrong Huang ◽  
Ling Shen ◽  
Li Yang ◽  
...  
Keyword(s):  
Inflammatory Responses ◽  
Astrocyte Activation ◽  
Hect Domain ◽  
P38 Inhibitor ◽  
Ubiquitin Protein Ligase ◽  
Primary Mouse ◽  
Lps Treatment

Abstract Background Astrocytes participate in innate inflammatory responses within the mammalian central nervous system (CNS). HECT domain E3 ubiquitin protein ligase 1 (HECTD1) functions during microglial activation, suggesting a connection with neuroinflammation. However, the potential role of HECTD1 in astrocytes remains largely unknown. Results Here, we demonstrated that HECTD1 was upregulated in primary mouse astrocytes after 100 ng/ml lipopolysaccharide (LPS) treatment. Genetic knockdown of HECTD1 in vitro or astrocyte-specific knockdown of HECTD1 in vivo suppressed LPS-induced astrocyte activation, whereas overexpression of HECTD1 in vitro facilitated LPS-induced astrocyte activation. Mechanistically, we established that LPS activated σ-1R-JNK/p38 pathway, and σ-1R antagonist BD1047, JNK inhibitor SP600125, or p38 inhibitor SB203580 reversed LPS-induced expression of HECTD1, thus restored LPS-induced astrocyte activation. In addition, FOXJ2 functioned as a transcription factor of HECTD1, and pretreatment of primary mouse astrocytes with BD1047, SB203580, and SP600125 significantly inhibited LPS-mediated translocation of FOXJ2 into the nucleus. Conclusions Overall, our present findings suggest that HECTD1 participates in LPS-induced astrocyte activation by activation of σ-1R-JNK/p38-FOXJ2 pathway and provide a potential therapeutic strategy for neuroinflammation induced by LPS or any other neuroinflammatory disorders.

scholarly journals Plant Physiology, 2021 Functional redox links between lumen thiol oxidoreductase1 and serine/threonine-protein kinase STN7

2021 ◽  
Author(s):  
Jianghao Wu ◽  
Liwei Rong ◽  
Weijun Lin ◽  
Lingxi Kong ◽  
Dengjie Wei ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Disulfide Bonds ◽  
Kinase Activity ◽  
Light Harvesting ◽  
Photosynthetic Electron Transport ◽  
State Transitions ◽  
Light Harvesting Complex ◽  
Light Harvesting Complex Ii

Abstract In response to changing light quantity and quality, photosynthetic organisms perform state transitions, a process which optimizes photosynthetic yield and mitigates photo-damage. The serine/threonine-protein kinase STN7 phosphorylates the light-harvesting complex of photosystem II (PSII; light-harvesting complex II), which then migrates from PSII to photosystem I (PSI), thereby rebalancing the light excitation energy between the photosystems and restoring the redox poise of the photosynthetic electron transport chain. Two conserved cysteines forming intra- or intermolecular disulfide bonds in the lumenal domain (LD) of STN7 are essential for the kinase activity although it is still unknown how activation of the kinase is regulated. In this study, we show lumen thiol oxidoreductase 1 (LTO1) is co-expressed with STN7 in Arabidopsis (Arabidopsis thaliana) and interacts with the LD of STN7 in vitro and in vivo. LTO1 contains thioredoxin (TRX)-like and vitamin K epoxide reductase domains which are related to the disulfide-bond formation system in bacteria. We further show that the TRX-like domain of LTO1 is able to oxidize the conserved lumenal cysteines of STN7 in vitro. In addition, loss of LTO1 affects the kinase activity of STN7 in Arabidopsis. Based on these results, we propose that LTO1 helps to maintain STN7 in an oxidized active state in state 2 through redox interactions between the lumenal cysteines of STN7 and LTO1.

scholarly journals Role for the Ran Binding Protein, Mog1p, in Saccharomyces cerevisiae SLN1-SKN7 Signal Transduction

2004 ◽  
Vol 3 (6) ◽  
pp. 1544-1556 ◽  
Author(s):  
Jade Mei-Yeh Lu ◽  
Robert J. Deschenes ◽  
Jan S. Fassler
Keyword(s):  
Signal Transduction ◽  
Transcription Factor ◽  
Osmotic Stress ◽  
Kinase Activity ◽  
Mitogen Activated Protein Kinase ◽  
Osmotic Response ◽  
Mitogen Activated Protein ◽  
Kinase Pathway

ABSTRACT Yeast Sln1p is an osmotic stress sensor with histidine kinase activity. Modulation of Sln1 kinase activity in response to changes in the osmotic environment regulates the activity of the osmotic response mitogen-activated protein kinase pathway and the activity of the Skn7p transcription factor, both important for adaptation to changing osmotic stress conditions. Many aspects of Sln1 function, such as how kinase activity is regulated to allow a rapid response to the continually changing osmotic environment, are not understood. To gain insight into Sln1p function, we conducted a two-hybrid screen to identify interactors. Mog1p, a protein that interacts with the yeast Ran1 homolog, Gsp1p, was identified in this screen. The interaction with Mog1p was characterized in vitro, and its importance was assessed in vivo. mog1 mutants exhibit defects in SLN1-SKN7 signal transduction and mislocalization of the Skn7p transcription factor. The requirement for Mog1p in normal localization of Skn7p to the nucleus does not fully account for the mog1-related defects in SLN1-SKN7 signal transduction, raising the possibility that Mog1p may play a role in Skn7 binding and activation of osmotic response genes.

scholarly journals Mice Lacking the Inhibitory Collagen Receptor LAIR-1 Exhibit a Mild Thrombocytosis and Hyperactive Platelets

2017 ◽  
Vol 37 (5) ◽  
pp. 823-835 ◽  
Author(s):  
Christopher W. Smith ◽  
Steven G. Thomas ◽  
Zaher Raslan ◽  
Pushpa Patel ◽  
Maxwell Byrne ◽  
...  
Keyword(s):  
Tyrosine Kinases ◽  
Kinase Activity ◽  
Thrombus Formation ◽  
Physiological Role ◽  
Src Family Kinase ◽  
Glycoprotein Vi ◽  
Collagen Receptor ◽  
Deficient Mice

Objective— Leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1) is a collagen receptor that belongs to the inhibitory immunoreceptor tyrosine-based inhibition motif–containing receptor family. It is an inhibitor of signaling via the immunoreceptor tyrosine-based activation motif–containing collagen receptor complex, glycoprotein VI-FcRγ-chain. It is expressed on hematopoietic cells, including immature megakaryocytes, but is not detectable on platelets. Although the inhibitory function of LAIR-1 has been described in leukocytes, its physiological role in megakaryocytes and in particular in platelet formation has not been explored. In this study, we investigate the role of LAIR-1 in megakaryocyte development and platelet production by generating LAIR-1–deficient mice. Approach and Results— Mice lacking LAIR-1 exhibit a significant increase in platelet counts, a prolonged platelet half-life in vivo, and increased proplatelet formation in vitro. Interestingly, platelets from LAIR-1–deficient mice exhibit an enhanced reactivity to collagen and the glycoprotein VI–specific agonist collagen-related peptide despite not expressing LAIR-1, and mice showed enhanced thrombus formation in the carotid artery after ferric chloride injury. Targeted deletion of LAIR-1 in mice results in an increase in signaling downstream of the glycoprotein VI–FcRγ-chain and integrin αIIbβ3 in megakaryocytes because of enhanced Src family kinase activity. Conclusions— Findings from this study demonstrate that ablation of LAIR-1 in megakaryocytes leads to increased Src family kinase activity and downstream signaling in response to collagen that is transmitted to platelets, rendering them hyper-reactive specifically to agonists that signal through Syk tyrosine kinases, but not to G-protein–coupled receptors.

Mitosis-specific phosphorylation of nucleolin by p34cdc2 protein kinase

1990 ◽  
Vol 10 (7) ◽  
pp. 3607-3618
Author(s):  
P Belenguer ◽  
M Caizergues-Ferrer ◽  
J C Labbé ◽  
M Dorée ◽  
F Amalric
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Control ◽  
Nucleolar Organizer ◽  
Serine Phosphorylation ◽  
Nucleolar Organizer Regions ◽  
Rdna Transcription ◽  
Amino Terminal ◽  
Nucleolar Chromatin

Nucleolin is a ubiquitous multifunctional protein involved in preribosome assembly and associated with both nucleolar chromatin in interphase and nucleolar organizer regions on metaphasic chromosomes in mitosis. Extensive nucleolin phosphorylation by a casein kinase (CKII) occurs on serine in growing cells. Here we report that while CKII phosphorylation is achieved in interphase, threonine phosphorylation occurs during mitosis. We provide evidence that this type of in vivo phosphorylation involves a mammalian homolog of the cell cycle control Cdc2 kinase. In vitro M-phase H1 kinase from starfish oocytes phosphorylated threonines in a TPXK motif present nine times in the amino-terminal part of the protein. The same sites which matched the p34cdc2 consensus phosphorylation sequence were used in vivo during mitosis. We propose that successive Cdc2 and CKII phosphorylation could modulate nucleolin function in controlling cell cycle-dependent nucleolar function and organization. Our results, along with previous studies, suggest that while serine phosphorylation is related to nucleolin function in the control of rDNA transcription, threonine phosphorylation is linked to mitotic reorganization of nucleolar chromatin.

The extracellular matrix of hybrids between melanoma cells and normal fibroblasts

1988 ◽  
Vol 91 (2) ◽  
pp. 281-286
Author(s):  
M.C. Copeman ◽  
H. Harris
Keyword(s):  
Extracellular Matrix ◽  
Protease Activity ◽  
Malignant Tumour ◽  
Melanoma Cells ◽  
Chromosome Loss ◽  
Type I ◽  
Chromosome 4 ◽  
Hybrid Cells

It has been shown that when malignant tumour cells are fused with normal fibroblasts the suppression of malignancy in the hybrids is linked to their ability to produce a collagenous extracellular matrix in vivo. When, as a consequence of chromosome loss, segregants arise that reacquire malignancy, these do not produce any detectable matrix. In this paper we examine the main components of the extracellular matrix produced in vitro by hybrids between malignant mouse melanoma cells and normal mouse fibroblasts. Hybrids in which malignancy is suppressed synthesize about ten times as much type 1 procollagen as the malignant segregants derived from them; they also retain more fibronectin in the cell layer and release less protease activity into the medium. Malignant segregants more closely resemble the parental melanoma cells in producing fibronectin and mainly types IV and V procollagen. When hybrid cells in which malignancy is initially suppressed are grown continuously in vitro, the production of type I procollagen declines, and the production of type V procollagen and the release of protease activity into the medium increase. These changes, which are associated with the loss from the hybrid cells of both copies of the chromosome 4 derived from the parental fibroblast, predict the reacquisition of malignancy when the cells are inoculated into mice. It is possible that one gene or set of genes located on chromosome 4 determines both the execution of the fibroblast differentiation programme and the suppression of malignancy.

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