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Chan GK, McGrath JA, Parsons M. Spatial activation of ezrin by epidermal growth factor receptor and focal adhesion kinase co-ordinates epithelial cell migration. Open Biol 2021; 11:210166. [PMID: 34375550 PMCID: PMC8354753 DOI: 10.1098/rsob.210166] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Epidermal growth factor receptor (EGFR) plays a critical role in the promotion of epithelial cell proliferation and migration. Previous studies have suggested a cooperative role between EGFR and integrin signalling pathways that enable efficient adhesion and migration but the mechanisms controlling this remain poorly defined. Here, we show that EGFR forms a complex with focal adhesion kinase in epithelial cells. Surprisingly, this complex enhances local Src activity at focal adhesions to promote phosphorylation of the cytoskeletal adaptor protein ezrin at Y478, leading to actomyosin contractility, suppression of focal adhesion dynamics and slower migration. We further demonstrate this regulation of Src is due to the suppression of PTP1B activity. Our data provide new insight into EGF-independent cooperation between EGFR and integrins and suggest transient interactions between these kinases at the leading edge of cells act to spatially control signalling to permit efficient motility.
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Affiliation(s)
- Grace K Chan
- Randall Centre for Cell and Molecular Biophysics, King's College London, Guy's Campus, London SE1 1UL, UK
| | - John A McGrath
- St Johns Institute of Dermatology, King's College London, Guy's Campus, London SE1 9RT, UK
| | - Maddy Parsons
- Randall Centre for Cell and Molecular Biophysics, King's College London, Guy's Campus, London SE1 1UL, UK
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2
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Poland SP, Chan GK, Levitt JA, Krstajić N, Erdogan AT, Henderson RK, Parsons M, Ameer-Beg SM. Multifocal multiphoton volumetric imaging approach for high-speed time-resolved Förster resonance energy transfer imaging in vivo. Opt Lett 2018; 43:6057-6060. [PMID: 30548010 PMCID: PMC6410918 DOI: 10.1364/ol.43.006057] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 10/29/2018] [Accepted: 11/01/2018] [Indexed: 05/29/2023]
Abstract
In this Letter, we will discuss the development of a multifocal multiphoton fluorescent lifetime imaging system where four individual fluorescent intensity and lifetime planes are acquired simultaneously, allowing us to obtain volumetric data without the need for sequential scanning at different axial depths. Using a phase-only spatial light modulator (SLM) with an appropriate algorithm to generate a holographic pattern, we project a beamlet array within a sample volume of a size, which can be preprogrammed by the user. We demonstrate the capabilities of the system to image live-cell interactions. While only four planes are shown, this technique can be rescaled to a large number of focal planes, enabling full 3D acquisition and reconstruction.
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Affiliation(s)
- Simon P. Poland
- Comprehensive Cancer Centre, School of Cancer and Pharmaceutical Sciences, Guy's Campus, King's College London, UK
| | - Grace K. Chan
- Randall Centre for Cell and Molecular Biophysics, Guy’s Campus, Kings College, UK
| | - James A. Levitt
- Comprehensive Cancer Centre, School of Cancer and Pharmaceutical Sciences, Guy's Campus, King's College London, UK
- Randall Centre for Cell and Molecular Biophysics, Guy’s Campus, Kings College, UK
| | - Nikola Krstajić
- Institute for Integrated Micro and Nano Systems, School of Engineering, University of Edinburgh, Edinburgh, UK
- EPSRC IRC “Hub” in Optical Molecular Sensing & Imaging, Centre for Inflammation Research, Queen’s Medical Research Institute, 47 Little France Crescent, University of Edinburgh, Edinburgh, UK
| | - Ahmet T. Erdogan
- Institute for Integrated Micro and Nano Systems, School of Engineering, University of Edinburgh, Edinburgh, UK
| | - Robert K. Henderson
- Institute for Integrated Micro and Nano Systems, School of Engineering, University of Edinburgh, Edinburgh, UK
| | - Maddy Parsons
- Randall Centre for Cell and Molecular Biophysics, Guy’s Campus, Kings College, UK
| | - Simon M. Ameer-Beg
- Comprehensive Cancer Centre, School of Cancer and Pharmaceutical Sciences, Guy's Campus, King's College London, UK
- Randall Centre for Cell and Molecular Biophysics, Guy’s Campus, Kings College, UK
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3
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Kim S, Park SY, Yong H, Famulski JK, Chae S, Lee JH, Kang CM, Saya H, Chan GK, Cho H. HBV X protein targets hBubR1, which induces dysregulation of the mitotic checkpoint. Oncogene 2008; 27:3457-64. [DOI: 10.1038/sj.onc.1210998] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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Chan GK, Deckelbaum RA, Bolivar I, Goltzman D, Karaplis AC. PTHrP inhibits adipocyte differentiation by down-regulating PPAR gamma activity via a MAPK-dependent pathway. Endocrinology 2001; 142:4900-9. [PMID: 11606458 DOI: 10.1210/endo.142.11.8515] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We examined the capacity of PTHrP to modulate the terminal differentiation of the preadipocytic cell line, 3T3-L1. These cells express endogenous PTHrP and its receptor, but expression levels were undetectable after differentiation into mature adipocytes. Cells stably overexpressing PTHrP failed to differentiate when induced to undergo adipogenesis and proliferated at a faster rate. MAPK activity was elevated in PTHrP-transfected 3T3-L1 cells, and treatment with the PKA inhibitor H-8 decreased this activity. Inhibition of MAPK kinase with PD098059 permitted terminal differentiation of PTHrP-transfected 3T3-L1 cells to proceed. Although PPAR gamma gene expression levels remained relatively constant in the PTHrP-transfected cells, PPAR gamma phosphorylation was enhanced. Furthermore, the capacity of PPAR gamma to stimulate transcription in the presence of troglitazone was diminished by PTHrP. Expression of the PPAR gamma-regulated adipocyte specific gene aP2 transiently rose and then fell in PTHrP-transfected cells. These results indicate that PTHrP can increase MAPK activity in 3T3-L1 cells via the PKA pathway, thereby enhancing PPAR gamma phosphorylation. This modification can inactivate the transcriptional enhancing activity of PPAR gamma and diminish the expression of adipocyte-specific genes. These studies therefore demonstrate that PTHrP may inhibit the terminal differentiation of preadipocytes and describe a molecular pathway by which this action can be achieved.
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Affiliation(s)
- G K Chan
- Division of Endocrinology, Department of Medicine, McGill University, Montréal, Québec, Canada H3T 1E2
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5
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Abstract
The mitotic checkpoint prevents cells with unaligned chromosomes from prematurely exiting mitosis by inhibiting the anaphase-promoting complex/cyclosome (APC/C) from targeting key proteins for ubiquitin-mediated proteolysis. We have examined the mechanism by which the checkpoint inhibits the APC/C by purifying an APC/C inhibitory factor from HeLa cells. We call this factor the mitotic checkpoint complex (MCC) as it consists of hBUBR1, hBUB3, CDC20, and MAD2 checkpoint proteins in near equal stoichiometry. MCC inhibitory activity is 3,000-fold greater than that of recombinant MAD2, which has also been shown to inhibit APC/C in vitro. Surprisingly, MCC is not generated from kinetochores, as it is also present and active in interphase cells. However, only APC/C isolated from mitotic cells was sensitive to inhibition by MCC. We found that the majority of the APC/C in mitotic lysates is associated with the MCC, and this likely contributes to the lag in ubiquitin ligase activity. Importantly, chromosomes can suppress the reactivation of APC/C. Chromosomes did not affect the inhibitory activity of MCC or the stimulatory activity of CDC20. We propose that the preformed interphase pool of MCC allows for rapid inhibition of APC/C when cells enter mitosis. Unattached kinetochores then target the APC/C for sustained inhibition by the MCC.
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Affiliation(s)
- V Sudakin
- Institute for Cancer Research, The Fox Chase Cancer Center, Philadelphia, PA 19111, USA
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McEwen BF, Chan GK, Zubrowski B, Savoian MS, Sauer MT, Yen TJ. CENP-E is essential for reliable bioriented spindle attachment, but chromosome alignment can be achieved via redundant mechanisms in mammalian cells. Mol Biol Cell 2001; 12:2776-89. [PMID: 11553716 PMCID: PMC59712 DOI: 10.1091/mbc.12.9.2776] [Citation(s) in RCA: 200] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
CENP-E is a kinesin-like protein that when depleted from mammalian kinetochores leads to mitotic arrest with a mixture of aligned and unaligned chromosomes. In the present study, we used immunofluorescence, video, and electron microscopy to demonstrate that depletion of CENP-E from kinetochores via antibody microinjection reduces kinetochore microtubule binding by 23% at aligned chromosomes, and severely reduces microtubule binding at unaligned chromosomes. Disruption of CENP-E function also reduces tension across the centromere, increases the incidence of spindle pole fragmentation, and results in monooriented chromosomes approaching abnormally close to the spindle pole. Nevertheless, chromosomes show typical patterns of congression, fast poleward motion, and oscillatory motions. Furthermore, kinetochores of aligned and unaligned chromosomes exhibit normal patterns of checkpoint protein localization. These data are explained by a model in which redundant mechanisms enable kinetochore microtubule binding and checkpoint monitoring in the absence of CENP-E at kinetochores, but where reduced microtubule-binding efficiency, exacerbated by poor positioning at the spindle poles, results in chronically monooriented chromosomes and mitotic arrest. Chromosome position within the spindle appears to be a critical determinant of CENP-E function at kinetochores.
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Affiliation(s)
- B F McEwen
- Division Molecular Medicine, Wadsworth Center, New York State Department of Health, Albany, NY 12201-0509, USA.
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Miao D, Tong XK, Chan GK, Panda D, McPherson PS, Goltzman D. Parathyroid hormone-related peptide stimulates osteogenic cell proliferation through protein kinase C activation of the Ras/mitogen-activated protein kinase signaling pathway. J Biol Chem 2001; 276:32204-13. [PMID: 11402023 DOI: 10.1074/jbc.m101084200] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We investigated the mechanisms of parathyroid hormone-related peptide (PTHrP)-mediated effects on osteogenic cells in primary rat bone marrow cell (BMC) cultures. We first demonstrated by reverse transcriptase-polymerase chain reaction and immunocytochemistry that BMCs express the type I parathyroid hormone/PTHrP receptor. Treatment with PTHrP increased osteogenic cell proliferation as determined by [(3)H]thymidine and bromodeoxyuridine incorporation and augmented osteogenic colonies. Immunocytochemistry and Western blotting revealed no direct effect on expression of the osteoblast markers, type I collagen, bone sialoprotein, and osteocalcin, indicating that PTHrP did not directly stimulate differentiation in this system. PTHrP increased mitogen-activated protein kinase (MAPK) activity in BMC and MAPK activity, and PTHrP-induced osteogenic cell proliferation could be blocked by the MEK inhibitor PD-098059. PTHrP also increased Ras activity in BMC. Although wortmannin and H8, inhibitors of phosphoinositol 3-kinase and protein kinase A, respectively, did not block PTHrP-stimulated Ras or MAPK activity, chelerythrin chloride, a known protein kinase C inhibitor, did block these PTHrP actions as well as PTHrP-induced osteogenic cell proliferation. These results demonstrate that PTHrP stimulates osteogenic cell proliferation in rat marrow mesenchymal progenitor cells through protein kinase C-dependent activation of the Ras and MAPK signaling pathway.
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Affiliation(s)
- D Miao
- Calcium Research Laboratory, Department of Medicine, McGill University Health Centre and McGill University, Montreal, Quebec H3A 1A1, Canada
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8
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Abstract
Mad1 was first identified in budding yeast as an essential component of the checkpoint system that monitors spindle assembly in mitosis and prevents premature anaphase onset. Using antibodies to the human homologue of Mad1 (HsMAD1), we have begun to characterize this protein in mammalian cells. HsMad1 is found localized at kinetochores in mitosis. The labeling is brightest in prometaphase and is absent from kinetochores at metaphase and anaphase. In cells where most chromosomes have reached the metaphase plate, those aligned at the plate show no labeling while remaining, unaligned chromosomes are still brightly labeled. We find HsMad1 associated with HsMad2. Association with p55CDC, a protein previously shown to bind HsMad2, was not detected. Surprisingly, unlike any other known mitotic checkpoint proteins, HsMad1 and HsMAD2 were found localized at nuclear pores throughout interphase. This was confirmed by co-labeling with an antibody to known nuclear pore complex proteins and by their co-purification with enriched nuclear envelope fractions. HsMad1 was identified serendipitously by its binding to a viral protein, HTLV-1 Tax, which affects transcription of viral and human proteins. The localization of HsMad1 to nuclear pore complexes suggests an alternate, non-mitotic role for the Mad1/Tax interaction in the viral transformation of cells.
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Affiliation(s)
- M S Campbell
- Fox Chase Cancer Center, Philadelphia, PA 19111, USA
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Marmorstein LY, Kinev AV, Chan GK, Bochar DA, Beniya H, Epstein JA, Yen TJ, Shiekhattar R. A human BRCA2 complex containing a structural DNA binding component influences cell cycle progression. Cell 2001; 104:247-57. [PMID: 11207365 DOI: 10.1016/s0092-8674(01)00209-4] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Germline mutations of the human BRCA2 gene confer susceptibility to breast cancer. Although the function of the BRCA2 protein remains to be determined, murine cells homozygous for BRCA2 inactivation display chromosomal aberrations. We have isolated a 2 MDa BRCA2-containing complex and identified a structural DNA binding component, designated as BRCA2-Associated Factor 35 (BRAF35). BRAF35 contains a nonspecific DNA binding HMG domain and a kinesin-like coiled coil domain. Similar to BRCA2, BRAF35 mRNA expression levels in mouse embryos are highest in proliferating tissues with high mitotic index. Strikingly, nuclear staining revealed a close association of BRAF35/BRCA2 complex with condensed chromatin coincident with histone H3 phosphorylation. Importantly, antibody microinjection experiments suggest a role for BRCA2/BRAF35 complex in modulation of cell cycle progression.
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Affiliation(s)
- L Y Marmorstein
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA
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Chan GK, Houweling L, Leet T, Martin C, Martin TC, Sandifer K, Yee AM. Conducting research in the emergency department: respect ED nurses' workload and recognize their contribution. J Emerg Nurs 2000; 26:626-7. [PMID: 11106469 DOI: 10.1067/men.2000.111529] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- G K Chan
- San Jose Medical Center, San Jose, CA 95112, USA.
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11
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Abstract
Here we show that human Zeste White 10 (Zw10) and Rough deal (Rod) are new components of the mitotic checkpoint, as cells lacking these proteins at kinetochores fail to arrest in mitosis when exposed to microtubule inhibitors. Checkpoint failure and premature mitotic exit may explain why cells defective for hZw10 and hRod divide with lagging chromosomes. As Zw10 and Rod are not conserved in yeast, our data, combined with an accompanying study of Drosophila Zw10 and Rod, indicate that metazoans may require an elaborate spindle checkpoint to monitor complex kinetochore functions.
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Affiliation(s)
- G K Chan
- Fox Chase Cancer Center, 7701 Burholme Avenue, Philadelphia, Pennsylvania 19111, USA
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12
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Affiliation(s)
- G K Chan
- University of California-San Francisco, School of Nursing 94143-0610, USA
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Bakken S, Cimino JJ, Haskell R, Kukafka R, Matsumoto C, Chan GK, Huff SM. Evaluation of the clinical LOINC (Logical Observation Identifiers, Names, and Codes) semantic structure as a terminology model for standardized assessment measures. J Am Med Inform Assoc 2000; 7:529-38. [PMID: 11062226 PMCID: PMC129661 DOI: 10.1136/jamia.2000.0070529] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
OBJECTIVE The purpose of this study was to test the adequacy of the Clinical LOINC (Logical Observation Identifiers, Names, and Codes) semantic structure as a terminology model for standardized assessment measures. METHODS After extension of the definitions, 1, 096 items from 35 standardized assessment instruments were dissected into the elements of the Clinical LOINC semantic structure. An additional coder dissected at least one randomly selected item from each instrument. When multiple scale types occurred in a single instrument, a second coder dissected one randomly selected item representative of each scale type. RESULTS The results support the adequacy of the Clinical LOINC semantic structure as a terminology model for standardized assessments. Using the revised definitions, the coders were able to dissect into the elements of Clinical LOINC all the standardized assessment items in the sample instruments. Percentage agreement for each element was as follows: component, 100 percent; property, 87.8 percent; timing, 82.9 percent; system/sample, 100 percent; scale, 92.6 percent; and method, 97.6 percent. DISCUSSION This evaluation was an initial step toward the representation of standardized assessment items in a manner that facilitates data sharing and re-use. Further clarification of the definitions, especially those related to time and property, is required to improve inter-rater reliability and to harmonize the representations with similar items already in LOINC.
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Affiliation(s)
- S Bakken
- Columbia University, New York, New York 10032, USA.
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Jablonski SA, Chan GK, Cooke CA, Earnshaw WC, Yen TJ. The hBUB1 and hBUBR1 kinases sequentially assemble onto kinetochores during prophase with hBUBR1 concentrating at the kinetochore plates in mitosis. Chromosoma 1998; 107:386-96. [PMID: 9914370 DOI: 10.1007/s004120050322] [Citation(s) in RCA: 136] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
The kinetochore binds an evolutionarily conserved set of checkpoint proteins that function to monitor whether chromosomes have aligned properly at the spindle equator. Human cells contain two related protein kinases, hBUB1 and hBUBR1, that appear to have evolved from a single ancestral BUB1 gene. We generated hBUB1- and hBUBR1-specific antibodies so that the localization patterns of these kinases could be directly compared. In the human U2OS osteosarcoma cell line, hBUB1 first appeared at kinetochores during early prophase before all kinetochores were occupied by hBUBR1 or CENP-F. Both proteins remained at kinetochores throughout mitosis but their staining intensity was reduced from anaphase onward. Kinetochores of unaligned chromosomes exhibited stronger hBUB1 and hBUBR1 staining. Immunoelectron microscopy showed that hBUBR1 appeared to be concentrated in the outer kinetochore plate and in some instances the inner plate as well. When chromosome spreads were examined by light microscopy, hBUB1 and hBUBR1 were coincident with CENP-E. This suggests that both kinases are concentrated near the surface of the kinetochore where they can monitor kinetochore-microtubule interactions.
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Affiliation(s)
- S A Jablonski
- Fox Chase Cancer Center, 7701 Burholme Avenue, Philadelphia, PA 19111, USA
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15
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Basu J, Logarinho E, Herrmann S, Bousbaa H, Li Z, Chan GK, Yen TJ, Sunkel CE, Goldberg ML. Localization of the Drosophila checkpoint control protein Bub3 to the kinetochore requires Bub1 but not Zw10 or Rod. Chromosoma 1998; 107:376-85. [PMID: 9914369 DOI: 10.1007/s004120050321] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
We report here the isolation and molecular characterization of the Drosophila homolog of the mitotic checkpoint control protein Bub3. The Drosophila Bub3 protein is associated with the centromere/kinetochore of chromosomes in larval neuroblasts whose spindle assembly checkpoints have been activated by incubation with the microtubule-depolymerizing agent colchicine. Drosophila Bub3 is also found at the kinetochore regions in mitotic larval neuroblasts and in meiotic primary and secondary spermatocytes, with the strong signal seen during prophase and prometaphase becoming increasingly weaker after the chromosomes have aligned at the metaphase plate. We further show that the localization of Bub3 to the kinetochore is disrupted by mutations in the gene encoding the Drosophila homolog of the spindle assembly checkpoint protein Bub1. Combined with recent findings showing that the kinetochore localization of Bub1 conversely depends upon Bub3, these results support the hypothesis that the spindle assembly checkpoint proteins exist as a multiprotein complex recruited as a unit to the kinetochore. In contrast, we demonstrate that the kinetochore constituents Zw10 and Rod are not needed for the binding of Bub3 to the kinetochore. This suggests that the kinetochore is assembled in at least two relatively independent pathways.
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Affiliation(s)
- J Basu
- Section of Genetics and Development, Biotechnology Building, Cornell University, Ithaca, NY 14853, USA
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16
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Chan GK, Schaar BT, Yen TJ. Characterization of the kinetochore binding domain of CENP-E reveals interactions with the kinetochore proteins CENP-F and hBUBR1. J Cell Biol 1998; 143:49-63. [PMID: 9763420 PMCID: PMC2132809 DOI: 10.1083/jcb.143.1.49] [Citation(s) in RCA: 207] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/1998] [Revised: 07/23/1998] [Indexed: 12/04/2022] Open
Abstract
We have identified a 350-amino acid domain in the kinetochore motor CENP-E that specifies kinetochore binding in mitosis but not during interphase. The kinetochore binding domain was used in a yeast two-hybrid screen to isolate interacting proteins that included the kinetochore proteins CENP-E, CENP-F, and hBUBR1, a BUB1-related kinase that was found to be mutated in some colorectal carcinomas (Cahill, D.P., C. Lengauer, J. Yu, G.J. Riggins, J.K. Wilson, S.D. Markowitz, K.W. Kinzler, and B. Vogelstein. 1998. Nature. 392:300-303). CENP-F, hBUBR1, and CENP-E assembled onto kinetochores in sequential order during late stages of the cell cycle. These proteins therefore define discrete steps along the kinetochore assembly pathway. Kinetochores of unaligned chromosome exhibited stronger hBUBR1 and CENP-E staining than those of aligned chromosomes. CENP-E and hBUBR1 remain colocalized at kinetochores until mid-anaphase when hBUBR1 localized to portions of the spindle midzone that did not overlap with CENP-E. As CENP-E and hBUBR1 can coimmunoprecipitate with each other from HeLa cells, they may function as a motor-kinase complex at kinetochores. However, the complex distribution pattern of hBUBR1 suggests that it may regulate multiple functions that include the kinetochore and the spindle midzone.
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Affiliation(s)
- G K Chan
- Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA
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17
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Gately DP, Hittle JC, Chan GK, Yen TJ. Characterization of ATM expression, localization, and associated DNA-dependent protein kinase activity. Mol Biol Cell 1998; 9:2361-74. [PMID: 9725899 PMCID: PMC25502 DOI: 10.1091/mbc.9.9.2361] [Citation(s) in RCA: 137] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/1997] [Accepted: 06/12/1998] [Indexed: 12/28/2022] Open
Abstract
Ataxia telangiectasia-mutated gene (ATM) is a 350-kDa protein whose function is defective in the autosomal recessive disorder ataxia telangiectasia (AT). Affinity-purified polyclonal antibodies were used to characterize ATM. Steady-state levels of ATM protein varied from undetectable in most AT cell lines to highly expressed in HeLa, U2OS, and normal human fibroblasts. Subcellular fractionation showed that ATM is predominantly a nuclear protein associated with the chromatin and nuclear matrix. ATM protein levels remained constant throughout the cell cycle and did not change in response to serum stimulation. Ionizing radiation had no significant effect on either the expression or distribution of ATM. ATM immunoprecipitates from HeLa cells and the human DNA-dependent protein kinase null cell line MO59J, but not from AT cells, phosphorylated the 34-kDa subunit of replication protein A (RPA) complex in a single-stranded and linear double-stranded DNA-dependent manner. Phosphorylation of p34 RPA occurred on threonine and serine residues. Phosphopeptide analysis demonstrates that the ATM-associated protein kinase phosphorylates p34 RPA on similar residues observed in vivo. The DNA-dependent protein kinase activity observed for ATM immunocomplexes, along with the association of ATM with chromatin, suggests that DNA damage can induce ATM or a stably associated protein kinase to phosphorylate proteins in the DNA damage response pathway.
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Affiliation(s)
- D P Gately
- Fox Chase Cancer Center, Philadelphia, Pennsylvania 19027, USA
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18
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Schaar BT, Chan GK, Maddox P, Salmon ED, Yen TJ. CENP-E function at kinetochores is essential for chromosome alignment. J Cell Biol 1997; 139:1373-82. [PMID: 9396744 PMCID: PMC2132614 DOI: 10.1083/jcb.139.6.1373] [Citation(s) in RCA: 250] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/1997] [Revised: 10/10/1997] [Indexed: 02/05/2023] Open
Abstract
CENP-E is a kinesin-like protein that binds to kinetochores and may provide functions that are critical for normal chromosome motility during mitosis. To directly test the in vivo function of CENP-E, we microinjected affinity-purified antibodies to block the assembly of CENP-E onto kinetochores and then examined the behavior of these chromosomes. Chromosomes lacking CENP-E at their kinetochores consistently exhibited two types of defects that blocked their alignment at the spindle equator. Chromosomes positioned near a pole remained mono-oriented as they were unable to establish bipolar microtubule connections with the opposite pole. Chromosomes within the spindle established bipolar connections that supported oscillations and normal velocities of kinetochore movement between the poles, but these bipolar connections were defective because they failed to align the chromosomes into a metaphase plate. Overexpression of a mutant that lacked the amino-terminal 803 amino acids of CENP-E was found to saturate limiting binding sites on kinetochores and competitively blocked endogenous CENP-E from assembling onto kinetochores. Chromosomes saturated with the truncated CENP-E mutant were never found to be aligned but accumulated at the poles or were strewn within the spindle as was the case when cells were microinjected with CENP-E antibodies. As the motor domain was contained within the portion of CENP-E that was deleted, the chromosomal defect is likely attributed to the loss of motor function. The combined data show that CENP-E provides kinetochore functions that are essential for monopolar chromosomes to establish bipolar connections and for chromosomes with connections to both spindle poles to align at the spindle equator. Both of these events rely on activities that are provided by CENP-E's motor domain.
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Affiliation(s)
- B T Schaar
- Cell and Molecular Biology Graduate Group, University of Pennsylvania, Philadelphia, Pennsylvania 19103, USA
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Chan GK. A gadget for the Begg technique. J Clin Orthod 1981; 15:357-358. [PMID: 6944313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
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Chan GK. Sliding yoke in the Begg technique. J Clin Orthod 1979; 13:704-5. [PMID: 298286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Chan GK. Begg stage 3--a suggestion. J Clin Orthod 1972; 6:524. [PMID: 4507400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Chan GK. A radiographic cephalometric appraisal of Chinese (Cantonese) males. Preliminary report. Dent Mag Oral Top 1969; 86:260. [PMID: 5263466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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Somani P, Fleming JG, Chan GK, Lum BK. Antagonism of epinephrine-induced cardiac arrhythmias by 4-(2-isopropylamino-1-hydroxyethyl)-methanesulfonanilide (MJ 1999) . J Pharmacol Exp Ther 1966; 151:32-7. [PMID: 5902176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
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