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Zhang J, Qiu R, Bieger BD, Oakley CE, Oakley BR, Egan MJ, Xiang X. Aspergillus SUMOylation mutants exhibit chromosome segregation defects including chromatin bridges. Genetics 2023; 225:iyad169. [PMID: 37724751 PMCID: PMC10697819 DOI: 10.1093/genetics/iyad169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 08/29/2023] [Accepted: 09/07/2023] [Indexed: 09/21/2023] Open
Abstract
Functions of protein SUMOylation remain incompletely understood in different cell types. Via forward genetics, here we identified ubaBQ247*, a loss-of-function mutation in a SUMO activation enzyme UbaB in the filamentous fungus Aspergillus nidulans. The ubaBQ247*, ΔubaB, and ΔsumO mutants all produce abnormal chromatin bridges, indicating the importance of SUMOylation in the completion of chromosome segregation. The bridges are enclosed by nuclear membrane containing peripheral nuclear pore complex proteins that normally get dispersed during mitosis, and the bridges are also surrounded by cytoplasmic microtubules typical of interphase cells. Time-lapse sequences further indicate that most bridges persist through interphase prior to the next mitosis, and anaphase chromosome segregation can produce new bridges that persist into the next interphase. When the first mitosis happens at a higher temperature of 42°C, SUMOylation deficiency produces not only chromatin bridges but also many abnormally shaped single nuclei that fail to divide. UbaB-GFP localizes to interphase nuclei just like the previously studied SumO-GFP, but the nuclear signals disappear during mitosis when the nuclear pores are partially open, and the signals reappear after mitosis. The nuclear localization is consistent with many SUMO targets being nuclear proteins. Finally, although the budding yeast SUMOylation machinery interacts with LIS1, a protein critical for dynein activation, loss of SUMOylation does not cause any obvious defect in dynein-mediated transport of nuclei and early endosomes, indicating that SUMOylation is unnecessary for dynein activation in A. nidulans.
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Affiliation(s)
- Jun Zhang
- Department of Biochemistry and Molecular Biology, The Uniformed Services University of the Health Sciences-F. Edward Hébert School of Medicine, Bethesda, MD 20814, USA
| | - Rongde Qiu
- Department of Biochemistry and Molecular Biology, The Uniformed Services University of the Health Sciences-F. Edward Hébert School of Medicine, Bethesda, MD 20814, USA
| | - Baronger D Bieger
- Department of Entomology and Plant Pathology, University of Arkansas Systems Division of Agriculture, Fayetteville, AR 72701, USA
| | - C Elizabeth Oakley
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045, USA
| | - Berl R Oakley
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045, USA
| | - Martin J Egan
- Department of Entomology and Plant Pathology, University of Arkansas Systems Division of Agriculture, Fayetteville, AR 72701, USA
| | - Xin Xiang
- Department of Biochemistry and Molecular Biology, The Uniformed Services University of the Health Sciences-F. Edward Hébert School of Medicine, Bethesda, MD 20814, USA
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2
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Zhang J, Qiu R, Bieger BD, Oakley CE, Oakley BR, Egan MJ, Xiang X. Aspergillus SUMOylation mutants have normal dynein function but exhibit chromatin bridges. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.16.537086. [PMID: 37131833 PMCID: PMC10153134 DOI: 10.1101/2023.04.16.537086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Functions of protein SUMOylation remain incompletely understood in different cell types. The budding yeast SUMOylation machinery interacts with LIS1, a protein critical for dynein activation, but dynein-pathway components were not identified as SUMO-targets in the filamentous fungus Aspergillus nidulans. Via A. nidulans forward genetics, here we identified ubaBQ247*, a loss-of-function mutation in a SUMO-activation enzyme UbaB. Colonies of the ubaBQ247*, ΔubaB and ΔsumO mutants looked similar and less healthy than the wild-type colony. In these mutants, about 10% of nuclei are connected by abnormal chromatin bridges, indicating the importance of SUMOylation in the completion of chromosome segregation. Nuclei connected by chromatin bridges are mostly in interphase, suggesting that these bridges do not prevent cell-cycle progression. UbaB-GFP localizes to interphase nuclei just like the previously studied SumO-GFP, but the nuclear signals disappear during mitosis when the nuclear pores are partially open, and the signals reappear after mitosis. The nuclear localization is consistent with many SUMO-targets being nuclear proteins, for example, topoisomerase II whose SUMOylation defect gives rise to chromatin bridges in mammalian cells. Unlike in mammalian cells, however, loss of SUMOylation in A. nidulans does not apparently affect the metaphase-to-anaphase transition, further highlighting differences in the requirements of SUMOylation in different cell types. Finally, loss of UbaB or SumO does not affect dynein- and LIS1-mediated early-endosome transport, indicating that SUMOylation is unnecessary for dynein or LIS1 function in A. nidulans.
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Affiliation(s)
- Jun Zhang
- Department of Biochemistry and Molecular Biology, The Uniformed Services University of the Health Sciences- F. Edward Hébert School of Medicine, Bethesda, Maryland 20814, USA
| | - Rongde Qiu
- Department of Biochemistry and Molecular Biology, The Uniformed Services University of the Health Sciences- F. Edward Hébert School of Medicine, Bethesda, Maryland 20814, USA
| | - Baronger D. Bieger
- Department of Entomology and Plant Pathology, University of Arkansas Systems Division of Agriculture, Fayetteville, AR, USA
| | - C. Elizabeth Oakley
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS, USA
| | - Berl R. Oakley
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS, USA
| | - Martin J. Egan
- Department of Entomology and Plant Pathology, University of Arkansas Systems Division of Agriculture, Fayetteville, AR, USA
| | - Xin Xiang
- Department of Biochemistry and Molecular Biology, The Uniformed Services University of the Health Sciences- F. Edward Hébert School of Medicine, Bethesda, Maryland 20814, USA
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3
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Wang ZJ, Dai ZZ, Hu MZ, Liu JN, Liang H, Shen MM, Zhu SJ, Sheng HJ, Gao J, Huang AL, Tang KF. Upregulation of TUBG1 expression promotes hepatocellular carcinoma development. MEDICAL ONCOLOGY (NORTHWOOD, LONDON, ENGLAND) 2023; 40:96. [PMID: 36792863 DOI: 10.1007/s12032-023-01966-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 02/01/2023] [Indexed: 02/17/2023]
Abstract
Tubulin γ-1 (TUBG1) is a highly conserved component of the centrosome and its deregulation is involved in the development of several types of cancer. However, the role of TUBG1 in hepatocellular carcinoma (HCC) remains unclear. In this study, we found that TUBG1 was upregulated in human HCC cells and tissues and that TUBG1 upregulation was associated with promoter hypomethylation in HCC tissues. TUBG1 knockdown suppressed the proliferation, invasion, and migration of HCC cells. While TUBG1 expression was positively correlated with CD4 + memory T lymphocyte infiltration, it was negatively correlated with CD4 + regulatory T-cell infiltration in human HCC tissues. Furthermore, TUBG1 expression was positively correlated with the expression of genes involved in cell division. Noticeably, high expression of TUBG1 was associated with poor prognosis in patients with HCC. Overall, our findings revealed that TUBG1 promotes hepatocarcinogenesis by increasing proliferation, invasion, and migration of HCC cells and may regulate T lymphocyte infiltration. The current findings provide important insights into TUBG1 regulation in HCC, which could provide new therapeutic targets for hepatocarcinoma which has a very high incidence and mortality rate worldwide.
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Affiliation(s)
- Zi-Jian Wang
- Key Laboratory of Molecular Biology for Infectious Diseases, Ministry of Education, Chongqing Medical University, Chongqing, 400016, People's Republic of China.,The First Clinical College, Chongqing Medical University, Chongqing, 400016, People's Republic of China
| | - Zhi-Zheng Dai
- Key Laboratory of Molecular Biology for Infectious Diseases, Ministry of Education, Chongqing Medical University, Chongqing, 400016, People's Republic of China
| | - Mei-Zhen Hu
- Key Laboratory of Molecular Biology for Infectious Diseases, Ministry of Education, Chongqing Medical University, Chongqing, 400016, People's Republic of China
| | - Jun-Nan Liu
- School of Basic Medicine, Chongqing Medical University, Chongqing, 400016, People's Republic of China
| | - Hang Liang
- School of Basic Medicine, Chongqing Medical University, Chongqing, 400016, People's Republic of China
| | - Mei-Mei Shen
- Department of Gastroenterology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, People's Republic of China
| | - Shu-Juan Zhu
- School of Basic Medicine, Chongqing Medical University, Chongqing, 400016, People's Republic of China
| | - Hua-Jun Sheng
- School of Basic Medicine, Chongqing Medical University, Chongqing, 400016, People's Republic of China
| | - Jian Gao
- Department of Gastroenterology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, People's Republic of China
| | - Ai-Long Huang
- Key Laboratory of Molecular Biology for Infectious Diseases, Ministry of Education, Chongqing Medical University, Chongqing, 400016, People's Republic of China
| | - Kai-Fu Tang
- Key Laboratory of Molecular Biology for Infectious Diseases, Ministry of Education, Chongqing Medical University, Chongqing, 400016, People's Republic of China.
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Sulimenko V, Dráberová E, Dráber P. γ-Tubulin in microtubule nucleation and beyond. Front Cell Dev Biol 2022; 10:880761. [PMID: 36158181 PMCID: PMC9503634 DOI: 10.3389/fcell.2022.880761] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Accepted: 08/03/2022] [Indexed: 11/13/2022] Open
Abstract
Microtubules composed of αβ-tubulin dimers are dynamic cytoskeletal polymers that play key roles in essential cellular processes such as cell division, organelle positioning, intracellular transport, and cell migration. γ-Tubulin is a highly conserved member of the tubulin family that is required for microtubule nucleation. γ-Tubulin, together with its associated proteins, forms the γ-tubulin ring complex (γ-TuRC), that templates microtubules. Here we review recent advances in the structure of γ-TuRC, its activation, and centrosomal recruitment. This provides new mechanistic insights into the molecular mechanism of microtubule nucleation. Accumulating data suggest that γ-tubulin also has other, less well understood functions. We discuss emerging evidence that γ-tubulin can form oligomers and filaments, has specific nuclear functions, and might be involved in centrosomal cross-talk between microtubules and microfilaments.
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Affiliation(s)
| | | | - Pavel Dráber
- *Correspondence: Vadym Sulimenko, ; Pavel Dráber,
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5
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Dráber P, Dráberová E. Dysregulation of Microtubule Nucleating Proteins in Cancer Cells. Cancers (Basel) 2021; 13:cancers13225638. [PMID: 34830792 PMCID: PMC8616210 DOI: 10.3390/cancers13225638] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 11/06/2021] [Accepted: 11/08/2021] [Indexed: 12/12/2022] Open
Abstract
Simple Summary The dysfunction of microtubule nucleation in cancer cells changes the overall cytoskeleton organization and cellular physiology. This review focuses on the dysregulation of the γ-tubulin ring complex (γ-TuRC) proteins that are essential for microtubule nucleation. Recent research on the high-resolution structure of γ-TuRC has brought new insight into the microtubule nucleation mechanism. We discuss the effect of γ-TuRC protein overexpression on cancer cell behavior and new drugs directed to γ-tubulin that may offer a viable alternative to microtubule-targeting agents currently used in cancer chemotherapy. Abstract In cells, microtubules typically nucleate from microtubule organizing centers, such as centrosomes. γ-Tubulin, which forms multiprotein complexes, is essential for nucleation. The γ-tubulin ring complex (γ-TuRC) is an efficient microtubule nucleator that requires additional centrosomal proteins for its activation and targeting. Evidence suggests that there is a dysfunction of centrosomal microtubule nucleation in cancer cells. Despite decades of molecular analysis of γ-TuRC and its interacting factors, the mechanisms of microtubule nucleation in normal and cancer cells remains obscure. Here, we review recent work on the high-resolution structure of γ-TuRC, which brings new insight into the mechanism of microtubule nucleation. We discuss the effects of γ-TuRC protein dysregulation on cancer cell behavior and new compounds targeting γ-tubulin. Drugs inhibiting γ-TuRC functions could represent an alternative to microtubule targeting agents in cancer chemotherapy.
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6
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Aspergillus fumigatus, One Uninucleate Species with Disparate Offspring. J Fungi (Basel) 2021; 7:jof7010030. [PMID: 33419224 PMCID: PMC7825634 DOI: 10.3390/jof7010030] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 12/22/2020] [Accepted: 12/29/2020] [Indexed: 12/18/2022] Open
Abstract
Establishment of a fungal infection due to Aspergillus fumigatus relies on the efficient germination of the airborne conidia once they penetrate the respiratory tract. However, the features of conidial germination have been poorly explored and understood in this fungal species as well as in other species of filamentous fungi. We show here that the germination of A. fumigatus is asynchronous. If the nutritional environment and extensive gene deletions can modify the germination parameters for A. fumigatus, the asynchrony is maintained in all germinative conditions tested. Even though the causes for this asynchrony of conidial germination remain unknown, asynchrony is essential for the completion of the biological cycle of this filamentous fungus.
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7
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Álvarez-Escribano I, Sasse C, Bok JW, Na H, Amirebrahimi M, Lipzen A, Schackwitz W, Martin J, Barry K, Gutiérrez G, Cea-Sánchez S, Marcos AT, Grigoriev IV, Keller NP, Braus GH, Cánovas D. Genome sequencing of evolved aspergilli populations reveals robust genomes, transversions in A. flavus, and sexual aberrancy in non-homologous end-joining mutants. BMC Biol 2019; 17:88. [PMID: 31711484 PMCID: PMC6844060 DOI: 10.1186/s12915-019-0702-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Accepted: 09/19/2019] [Indexed: 01/19/2023] Open
Abstract
Background Aspergillus spp. comprises a very diverse group of lower eukaryotes with a high relevance for industrial applications and clinical implications. These multinucleate species are often cultured for many generations in the laboratory, which can unknowingly propagate hidden genetic mutations. To assess the likelihood of such events, we studied the genome stability of aspergilli by using a combination of mutation accumulation (MA) lines and whole genome sequencing. Results We sequenced the whole genomes of 30 asexual and 10 sexual MA lines of three Aspergillus species (A. flavus, A. fumigatus and A. nidulans) and estimated that each MA line accumulated mutations for over 4000 mitoses during asexual cycles. We estimated mutation rates of 4.2 × 10−11 (A. flavus), 1.1 × 10−11 (A. fumigatus) and 4.1 × 10−11 (A. nidulans) per site per mitosis, suggesting that the genomes are very robust. Unexpectedly, we found a very high rate of GC → TA transversions only in A. flavus. In parallel, 30 asexual lines of the non-homologous end-joining (NHEJ) mutants of the three species were also allowed to accumulate mutations for the same number of mitoses. Sequencing of these NHEJ MA lines gave an estimated mutation rate of 5.1 × 10−11 (A. flavus), 2.2 × 10−11 (A. fumigatus) and 4.5 × 10−11 (A. nidulans) per base per mitosis, which is slightly higher than in the wild-type strains and some ~ 5–6 times lower than in the yeasts. Additionally, in A. nidulans, we found a NHEJ-dependent interference of the sexual cycle that is independent of the accumulation of mutations. Conclusions We present for the first time direct counts of the mutation rate of filamentous fungal species and find that Aspergillus genomes are very robust. Deletion of the NHEJ machinery results in a slight increase in the mutation rate, but at a rate we suggest is still safe to use for biotechnology purposes. Unexpectedly, we found GC→TA transversions predominated only in the species A. flavus, which could be generated by the hepatocarcinogen secondary metabolite aflatoxin. Lastly, a strong effect of the NHEJ mutation in self-crossing was observed and an increase in the mutations of the asexual lines was quantified.
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Affiliation(s)
- Isidro Álvarez-Escribano
- Department of Genetics, Faculty of Biology, University of Seville, Seville, Spain.,Present Address: Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas y Universidad de Sevilla, Seville, Spain
| | - Christoph Sasse
- Department of Molecular Microbiology and Genetics and Göttingen Center for Molecular Biosciences (GZMB), Georg-August-University, Göttingen, Germany
| | - Jin Woo Bok
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, USA
| | - Hyunsoo Na
- US Department of Energy Joint Genome Institute, Walnut Creek, CA, USA
| | | | - Anna Lipzen
- US Department of Energy Joint Genome Institute, Walnut Creek, CA, USA
| | - Wendy Schackwitz
- US Department of Energy Joint Genome Institute, Walnut Creek, CA, USA
| | - Joel Martin
- US Department of Energy Joint Genome Institute, Walnut Creek, CA, USA
| | - Kerrie Barry
- US Department of Energy Joint Genome Institute, Walnut Creek, CA, USA
| | - Gabriel Gutiérrez
- Department of Genetics, Faculty of Biology, University of Seville, Seville, Spain
| | - Sara Cea-Sánchez
- Department of Genetics, Faculty of Biology, University of Seville, Seville, Spain
| | - Ana T Marcos
- Department of Genetics, Faculty of Biology, University of Seville, Seville, Spain.,Present Address: Instituto para el Estudio de la Reproducción Humana (Inebir), Avda de la Cruz Roja 1, 41009, Sevilla, Spain
| | - Igor V Grigoriev
- US Department of Energy Joint Genome Institute, Walnut Creek, CA, USA.,Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA, USA
| | - Nancy P Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, USA.,Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA
| | - Gerhard H Braus
- Department of Molecular Microbiology and Genetics and Göttingen Center for Molecular Biosciences (GZMB), Georg-August-University, Göttingen, Germany
| | - David Cánovas
- Department of Genetics, Faculty of Biology, University of Seville, Seville, Spain.
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8
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Chumová J, Kourová H, Trögelová L, Halada P, Binarová P. Microtubular and Nuclear Functions of γ-Tubulin: Are They LINCed? Cells 2019; 8:cells8030259. [PMID: 30893853 PMCID: PMC6468392 DOI: 10.3390/cells8030259] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 03/07/2019] [Accepted: 03/14/2019] [Indexed: 01/02/2023] Open
Abstract
γ-Tubulin is a conserved member of the tubulin superfamily with a function in microtubule nucleation. Proteins of γ-tubulin complexes serve as nucleation templates as well as a majority of other proteins contributing to centrosomal and non-centrosomal nucleation, conserved across eukaryotes. There is a growing amount of evidence of γ-tubulin functions besides microtubule nucleation in transcription, DNA damage response, chromatin remodeling, and on its interactions with tumor suppressors. However, the molecular mechanisms are not well understood. Furthermore, interactions with lamin and SUN proteins of the LINC complex suggest the role of γ-tubulin in the coupling of nuclear organization with cytoskeletons. γ-Tubulin that belongs to the clade of eukaryotic tubulins shows characteristics of both prokaryotic and eukaryotic tubulins. Both human and plant γ-tubulins preserve the ability of prokaryotic tubulins to assemble filaments and higher-order fibrillar networks. γ-Tubulin filaments, with bundling and aggregating capacity, are suggested to perform complex scaffolding and sequestration functions. In this review, we discuss a plethora of γ-tubulin molecular interactions and cellular functions, as well as recent advances in understanding the molecular mechanisms behind them.
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Affiliation(s)
- Jana Chumová
- Institute of Microbiology of the Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague, Czech Republic.
| | - Hana Kourová
- Institute of Microbiology of the Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague, Czech Republic.
| | - Lucie Trögelová
- Institute of Microbiology of the Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague, Czech Republic.
| | - Petr Halada
- Institute of Microbiology of the Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague, Czech Republic.
| | - Pavla Binarová
- Institute of Microbiology of the Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague, Czech Republic.
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9
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Rosselló CA, Lindström L, Eklund G, Corvaisier M, Kristensson MA. γ-Tubulin⁻γ-Tubulin Interactions as the Basis for the Formation of a Meshwork. Int J Mol Sci 2018; 19:ijms19103245. [PMID: 30347727 PMCID: PMC6214090 DOI: 10.3390/ijms19103245] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 10/02/2018] [Accepted: 10/16/2018] [Indexed: 12/14/2022] Open
Abstract
In cytoplasm, protein γ-tubulin joins with various γ-tubulin complex proteins (GCPs) to form a heterotetramer γ-tubulin small complex (γ-TuSC) that can grow into a ring-shaped structure called the γ-tubulin ring complex (γ-TuRC). Both γ-TuSC and γ-TuRC are required for microtubule nucleation. Recent knowledge on γ-tubulin with regard to its cellular functions beyond participation in its creation of microtubules suggests that this protein forms a cellular meshwork. The present review summarizes the recognized functions of γ-tubulin and aims to unite the current views on this protein.
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Affiliation(s)
- Catalina Ana Rosselló
- Molecular Pathology, Department of Translational Medicine, Lund University, Skåne University Hospital, 20502 Malmö, Sweden.
| | - Lisa Lindström
- Molecular Pathology, Department of Translational Medicine, Lund University, Skåne University Hospital, 20502 Malmö, Sweden.
| | - Greta Eklund
- Molecular Pathology, Department of Translational Medicine, Lund University, Skåne University Hospital, 20502 Malmö, Sweden.
| | - Matthieu Corvaisier
- Molecular Pathology, Department of Translational Medicine, Lund University, Skåne University Hospital, 20502 Malmö, Sweden.
| | - Maria Alvarado Kristensson
- Molecular Pathology, Department of Translational Medicine, Lund University, Skåne University Hospital, 20502 Malmö, Sweden.
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10
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Alvarado-Kristensson M. γ-tubulin as a signal-transducing molecule and meshwork with therapeutic potential. Signal Transduct Target Ther 2018; 3:24. [PMID: 30221013 PMCID: PMC6137058 DOI: 10.1038/s41392-018-0021-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Revised: 04/23/2018] [Accepted: 05/06/2018] [Indexed: 01/05/2023] Open
Abstract
Knowledge of γ-tubulin is increasing with regard to the cellular functions of this protein beyond its participation in microtubule nucleation. γ-Tubulin expression is altered in various malignancies, and changes in the TUBG1 gene have been found in patients suffering from brain malformations. This review recapitulates the known functions of γ-tubulin in cellular homeostasis and discusses the possible influence of the protein on disease development and cancer.
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Affiliation(s)
- Maria Alvarado-Kristensson
- Molecular Pathology, Department of Translational Medicine, Lund University, Skåne University Hospital, Malmö, 20502 Sweden
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11
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Paolillo V, Jenkinson C, Horio T, Oakley B. Cyclins in aspergilli: Phylogenetic and functional analyses of group I cyclins. Stud Mycol 2018; 91:1-22. [PMID: 30104814 PMCID: PMC6078057 DOI: 10.1016/j.simyco.2018.06.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
We have identified the cyclin domain-containing proteins encoded by the genomes of 17 species of Aspergillus as well as 15 members of other genera of filamentous ascomycetes. Phylogenetic analyses reveal that the cyclins fall into three groups, as in other eukaryotic phyla, and, more significantly, that they are remarkably conserved in these fungi. All 32 species examined, for example, have three group I cyclins, cyclins that are particularly important because they regulate the cell cycle, and these are highly conserved. Within the group I cyclins there are three distinct clades, and each fungus has a single member of each clade. These findings are in marked contrast to the yeasts Saccharomyces cerevisiae, Schizosaccharomyces pombe, and Candida albicans, which have more numerous group I cyclins. These results indicate that findings on cyclin function made with a model Aspergillus species, such as A. nidulans, are likely to apply to other Aspergilli and be informative for a broad range of filamentous ascomycetes. In this regard, we note that the functions of only one Aspergillus group I cyclin have been analysed (NimECyclin B of A. nidulans). We have consequently carried out an analysis of the members of the other two clades using A. nidulans as our model. We have found that one of these cyclins, PucA, is essential, but deletion of PucA in a strain carrying a deletion of CdhA, an activator of the anaphase promoting complex/cyclosome (APC/C), is not lethal. These data, coupled with data from heterokaryon rescue experiments, indicate that PucA is an essential G1/S cyclin that is required for the inactivation of the APC/C-CdhA, which, in turn, allows the initiation of the S phase of the cell cycle. Our data also reveal that PucA has additional, non-essential, roles in the cell cycle in interphase. The A. nidulans member of the third clade (AN2137) has not previously been named or analyzed. We designate this gene clbA. ClbA localizes to kinetochores from mid G2 until just prior to chromosomal condensation. Deletion of clbA does not affect viability. However, by using a regulatable promoter system new to Aspergillus, we have found that expression of a version of ClbA in which the destruction box sequences have been removed is lethal and causes a mitotic arrest and a high frequency of non-disjunction. Thus, although ClbA is not essential, its timely destruction is essential for viability, chromosomal disjunction, and successful completion of mitosis.
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Affiliation(s)
- V. Paolillo
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Ave., Lawrence, KS 66045, USA
| | - C.B. Jenkinson
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Ave., Lawrence, KS 66045, USA
| | - T. Horio
- Department of Natural Sciences, Nippon Sport Science University, Yokohama, Japan
| | - B.R. Oakley
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Ave., Lawrence, KS 66045, USA
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12
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Secretory Vesicle Polar Sorting, Endosome Recycling and Cytoskeleton Organization Require the AP-1 Complex in Aspergillus nidulans. Genetics 2018; 209:1121-1138. [PMID: 29925567 DOI: 10.1534/genetics.118.301240] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Accepted: 06/19/2018] [Indexed: 11/18/2022] Open
Abstract
The AP-1 complex is essential for membrane protein traffic via its role in the pinching-off and sorting of secretory vesicles (SVs) from the trans-Golgi and/or endosomes. While its essentiality is undisputed in metazoa, its role in simpler eukaryotes seems less clear. Here, we dissect the role of AP-1 in the filamentous fungus Aspergillus nidulans and show that it is absolutely essential for growth due to its role in clathrin-dependent maintenance of polar traffic of specific membrane cargoes toward the apex of growing hyphae. We provide evidence that AP-1 is involved in both anterograde sorting of RabERab11-labeled SVs and RabA/BRab5-dependent endosome recycling. Additionally, AP-1 is shown to be critical for microtubule and septin organization, further rationalizing its essentiality in cells that face the challenge of cytoskeleton-dependent polarized cargo traffic. This work also opens a novel issue on how nonpolar cargoes, such as transporters, are sorted to the eukaryotic plasma membrane.
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Ámon J, Keisham K, Bokor E, Kelemen E, Vágvölgyi C, Hamari Z. Sterigmatocystin production is restricted to hyphae located in the proximity of hülle cells. J Basic Microbiol 2018; 58:590-596. [PMID: 29733450 DOI: 10.1002/jobm.201800020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Revised: 04/19/2018] [Accepted: 04/22/2018] [Indexed: 12/20/2022]
Abstract
Aspergillus nidulans produces sterigmatocystin, a secondary metabolite mycotoxin, for the protection of its reproductive structures. Previous studies on grazing behavior of fungivore arthropods, regulation of sexual development, and secondary metabolite biosynthesis have revealed the association of sterigmatocystin biosynthesis with sexual reproduction, but the spatial distribution of sterigmatocystin producing hyphae within the colony has never been investigated. In this work, we aimed to locate the site of sterigmatocystin production within the colony by employing a yCFP reporter system. We demonstrated that the stcO promoter is active only in vegetative hyphae that surround groups of hülle cells and the activity decreases and eventually ceases as the distance between the hypha and the hülle cells increases. This phenomenon indicates that the vegetative mycelium might consist of morphologically uniform, but functionally different hyphae.
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Affiliation(s)
- Judit Ámon
- Faculty of Science and Informatics, Department of Microbiology, University of Szeged, Szeged, Hungary
| | - Kabichandra Keisham
- Faculty of Science and Informatics, Department of Microbiology, University of Szeged, Szeged, Hungary
| | - Eszter Bokor
- Faculty of Science and Informatics, Department of Microbiology, University of Szeged, Szeged, Hungary
| | - Evelyn Kelemen
- Faculty of Science and Informatics, Department of Microbiology, University of Szeged, Szeged, Hungary
| | - Csaba Vágvölgyi
- Faculty of Science and Informatics, Department of Microbiology, University of Szeged, Szeged, Hungary
| | - Zsuzsanna Hamari
- Faculty of Science and Informatics, Department of Microbiology, University of Szeged, Szeged, Hungary
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Egan MJ, McClintock MA, Hollyer IHL, Elliott HL, Reck-Peterson SL. Cytoplasmic dynein is required for the spatial organization of protein aggregates in filamentous fungi. Cell Rep 2016; 11:201-9. [PMID: 25865884 DOI: 10.1016/j.celrep.2015.03.028] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 02/10/2015] [Accepted: 03/11/2015] [Indexed: 01/01/2023] Open
Abstract
Eukaryotes have evolved multiple strategies for maintaining cellular protein homeostasis. One such mechanism involves neutralization of deleterious protein aggregates via their defined spatial segregation. Here, using the molecular disaggregase Hsp104 as a marker for protein aggregation, we describe the spatial and temporal dynamics of protein aggregates in the filamentous fungus Aspergillus nidulans. Filamentous fungi, such as A. nidulans, are a diverse group of species of major health and economic importance and also serve as model systems for studying highly polarized eukaryotic cells. We find that microtubules promote the formation of Hsp104-positive aggregates, which coalesce into discrete subcellular structures in a process dependent on the microtubule-based motor cytoplasmic dynein. Finally, we find that impaired clearance of these inclusions negatively impacts retrograde trafficking of endosomes, a conventional dynein cargo, indicating that microtubule-based transport can be overwhelmed by chronic cellular stress.
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Oakley BR, Paolillo V, Zheng Y. γ-Tubulin complexes in microtubule nucleation and beyond. Mol Biol Cell 2015; 26:2957-62. [PMID: 26316498 PMCID: PMC4551311 DOI: 10.1091/mbc.e14-11-1514] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 07/02/2015] [Accepted: 07/02/2015] [Indexed: 01/07/2023] Open
Abstract
Tremendous progress has been made in understanding the functions of γ-tubulin and, in particular, its role in microtubule nucleation since the publication of its discovery in 1989. The structure of γ-tubulin has been determined, and the components of γ-tubulin complexes have been identified. Significant progress in understanding the structure of the γ-tubulin ring complex and its components has led to a persuasive model for how these complexes nucleate microtubule assembly. At the same time, data have accumulated that γ-tubulin has important but less well understood functions that are not simply a consequence of its function in microtubule nucleation. These include roles in the regulation of plus-end microtubule dynamics, gene regulation, and mitotic and cell cycle regulation. Finally, evidence is emerging that γ-tubulin mutations or alterations of γ-tubulin expression play an important role in certain types of cancer and in other diseases.
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Affiliation(s)
- Berl R Oakley
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045
| | - Vitoria Paolillo
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045
| | - Yixian Zheng
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD 21218
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Overexpression and Nucleolar Localization of γ-Tubulin Small Complex Proteins GCP2 and GCP3 in Glioblastoma. J Neuropathol Exp Neurol 2015; 74:723-42. [PMID: 26079448 DOI: 10.1097/nen.0000000000000212] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The expression, cellular distribution, and subcellular sorting of the microtubule (MT)-nucleating γ-tubulin small complex (γTuSC) proteins, GCP2 and GCP3, were studied in human glioblastoma cell lines and in clinical tissue samples representing all histologic grades of adult diffuse astrocytic gliomas (n = 54). Quantitative real-time polymerase chain reaction revealed a significant increase in the expression of GCP2 and GCP3 transcripts in glioblastoma cells versus normal human astrocytes; these were associated with higher amounts of both γTuSC proteins. GCP2 and GCP3 were concentrated in the centrosomes in interphase glioblastoma cells, but punctate and diffuse localizations were also detected in the cytosol and nuclei/nucleoli. Nucleolar localization was fixation dependent. GCP2 and GCP3 formed complexes with γ-tubulin in the nucleoli as confirmed by reciprocal immunoprecipitation experiments and immunoelectron microscopy. GCP2 and GCP3 depletion caused accumulation of cells in G2/M and mitotic delay but did not affect nucleolar integrity. Overexpression of GCP2 antagonized the inhibitory effect of the CDK5 regulatory subunit-associated tumor suppressor protein 3 (C53) on DNA damage G2/M checkpoint activity. Tumor cell GCP2 and GCP3 immunoreactivity was significantly increased over that in normal brains in glioblastoma samples; it was also associated with microvascular proliferation. These findings suggest that γTuSC protein dysregulation in glioblastomas may be linked to altered transcriptional checkpoint activity or interaction with signaling pathways associated with a malignant phenotype.
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Katsetos CD, Reginato MJ, Baas PW, D'Agostino L, Legido A, Tuszyn Ski JA, Dráberová E, Dráber P. Emerging microtubule targets in glioma therapy. Semin Pediatr Neurol 2015; 22:49-72. [PMID: 25976261 DOI: 10.1016/j.spen.2015.03.009] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Major advances in the genomics and epigenomics of diffuse gliomas and glioblastoma to date have not been translated into effective therapy, necessitating pursuit of alternative treatment approaches for these therapeutically challenging tumors. Current knowledge of microtubules in cancer and the development of new microtubule-based treatment strategies for high-grade gliomas are the topic in this review article. Discussed are cellular, molecular, and pharmacologic aspects of the microtubule cytoskeleton underlying mitosis and interactions with other cellular partners involved in cell cycle progression, directional cell migration, and tumor invasion. Special focus is placed on (1) the aberrant overexpression of βIII-tubulin, a survival factor associated with hypoxic tumor microenvironment and dynamic instability of microtubules; (2) the ectopic overexpression of γ-tubulin, which in addition to its conventional role as a microtubule-nucleating protein has recently emerged as a transcription factor interacting with oncogenes and kinases; (3) the microtubule-severing ATPase spastin and its emerging role in cell motility of glioblastoma cells; and (4) the modulating role of posttranslational modifications of tubulin in the context of interaction of microtubules with motor proteins. Specific antineoplastic strategies discussed include downregulation of targeted molecules aimed at achieving a sensitization effect on currently used mainstay therapies. The potential role of new classes of tubulin-binding agents and ATPase inhibitors is also examined. Understanding the cellular and molecular mechanisms underpinning the distinct behaviors of microtubules in glioma tumorigenesis and drug resistance is key to the discovery of novel molecular targets that will fundamentally change the prognostic outlook of patients with diffuse high-grade gliomas.
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Affiliation(s)
- Christos D Katsetos
- Department of Pediatrics, Drexel University College of Medicine, Section of Neurology and Pediatric Neuro-oncology Program, St Christopher's Hospital for Children, Philadelphia, PA; Department of Pathology and Laboratory Medicine, Drexel University College of Medicine, Philadelphia, PA.
| | - Mauricio J Reginato
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA
| | - Peter W Baas
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA
| | - Luca D'Agostino
- Department of Pediatrics, Drexel University College of Medicine, Section of Neurology and Pediatric Neuro-oncology Program, St Christopher's Hospital for Children, Philadelphia, PA
| | - Agustin Legido
- Department of Pediatrics, Drexel University College of Medicine, Section of Neurology and Pediatric Neuro-oncology Program, St Christopher's Hospital for Children, Philadelphia, PA
| | - Jack A Tuszyn Ski
- Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, Alberta, Canada; Department of Physics, University of Alberta, Edmonton, Alberta, Canada
| | - Eduarda Dráberová
- Department of Biology of Cytoskeleton, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Pavel Dráber
- Department of Biology of Cytoskeleton, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
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Edgerton H, Paolillo V, Oakley BR. Spatial regulation of the spindle assembly checkpoint and anaphase-promoting complex in Aspergillus nidulans. Mol Microbiol 2014; 95:442-57. [PMID: 25417844 DOI: 10.1111/mmi.12871] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/13/2014] [Indexed: 11/29/2022]
Abstract
The spindle assembly checkpoint (SAC) plays a critical role in preventing mitotic errors by inhibiting anaphase until all kinetochores are correctly attached to spindle microtubules. In spite of the economic and medical importance of filamentous fungi, relatively little is known about the behavior of SAC proteins in these organisms. In our efforts to understand the role of γ-tubulin in cell cycle regulation, we have created functional fluorescent protein fusions of four SAC proteins in Aspergillus nidulans, the homologs of Mad2, Mps1, Bub1/BubR1 and Bub3. Time-lapse imaging reveals that SAC proteins are in distinct compartments of the cell until early mitosis when they co-localize at the spindle pole body. SAC activity is, thus, spatially regulated in A. nidulans. Likewise, Cdc20, an activator of the anaphase-promoting complex/cyclosome, is excluded from interphase nuclei, but enters nuclei at mitotic onset and accumulates to a higher level in mitotic nuclei than in the surrounding nucleoplasm before leaving in anaphase/telophase. The activity of this critical cell cycle regulatory complex is likely regulated by the location of Cdc20. Finally, the γ-tubulin mutation mipAD159 causes a nuclear-specific failure of nuclear localization of Mps1 and Bub1/R1 but not of Cdc20, Bub3 or Mad2.
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Affiliation(s)
- Heather Edgerton
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Ave., Lawrence, KS, 66045, USA
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Restraint of the G2/M transition by the SR/RRM family mRNA shuttling binding protein SNXAHRB1 in Aspergillus nidulans. Genetics 2014; 198:617-33. [PMID: 25104516 DOI: 10.1534/genetics.114.167445] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Control of the eukaryotic G2/M transition by CDC2/CYCLINB is tightly regulated by protein-protein interactions, protein phosphorylations, and nuclear localization of CDC2/CYCLINB. We previously reported a screen, in Aspergillus nidulans, for extragenic suppressors of nimX2(cdc2) that resulted in the identification of the cold-sensitive snxA1 mutation. We demonstrate here that snxA1 suppresses defects in regulators of the CDK1 mitotic induction pathway, including nimX2(cdc) (2), nimE6(cyclinB), and nimT23(cdc) (25), but does not suppress G2-arresting nimA1/nimA5 mutations, the S-arresting nimE10(cyclinB) mutation, or three other G1/S phase mutations. snxA encodes the A. nidulans homolog of Saccharomyces cerevisiae Hrb1/Gbp2; nonessential shuttling messenger RNA (mRNA)-binding proteins belonging to the serine-arginine-rich (SR) and RNA recognition motif (RRM) protein family; and human heterogeneous ribonucleoprotein-M, a spliceosomal component involved in pre-mRNA processing and alternative splicing. snxA(Hrb) (1) is nonessential, its deletion phenocopies the snxA1 mutation, and its overexpression rescues snxA1 and ΔsnxA mutant phenotypes. snxA1 and a second allele isolated in this study, snxA2, are hypomorphic mutations that result from decreased transcript and protein levels, suggesting that snxA acts normally to restrain cell cycle progression. SNXA(HRB1) is predominantly nuclear, but is not retained in the nucleus during the partially closed mitosis of A. nidulans. We show that the snxA1 mutation does not suppress nimX2 by altering NIMX2(CDC2)/NIME(CYCLINB) kinase activity and that snxA1 or ΔsnxA alter localization patterns of NIME(CYCLINB) at the restrictive temperatures for snxA1 and nimX2. Together, these findings suggest a novel and previously unreported role of an SR/RRM family protein in cell cycle regulation, specifically in control of the CDK1 mitotic induction pathway.
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Edzuka T, Yamada L, Kanamaru K, Sawada H, Goshima G. Identification of the augmin complex in the filamentous fungus Aspergillus nidulans. PLoS One 2014; 9:e101471. [PMID: 25003582 PMCID: PMC4086812 DOI: 10.1371/journal.pone.0101471] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 06/06/2014] [Indexed: 11/19/2022] Open
Abstract
Augmin is a protein complex that binds to spindle microtubules (MTs), recruits the potent MT nucleator, γ-tubulin, and thereby promotes the centrosome-independent MT generation within mitotic and meiotic spindles. Augmin is essential for acentrosomal spindle assembly, which is commonly observed during mitosis in plants and meiosis in female animals. In many animal somatic cells that possess centrosomes, the centrosome- and augmin-dependent mechanisms work cooperatively for efficient spindle assembly and cytokinesis. Yeasts have lost the augmin genes during evolution. It is hypothesized that their robust MT nucleation from the spindle pole body (SPB), the centrosome-equivalent structure in fungi, compensates for the lack of augmin. Intriguingly, however, a gene homologous to an augmin subunit (Aug6/AUGF) has been found in the genome of filamentous fungi, which has the SPB as a robust MT nucleation centre. Here, we aimed to clarify if the augmin complex is present in filamentous fungi and to identify its role in mitosis. By analysing the Aug6-like gene in the filamentous fungus Aspergillus nidulans, we found that it forms a large complex with several other proteins that share weak but significant homology to known augmin subunits. In A. nidulans, augmin was enriched at the SPB and also associated with spindle MTs during mitosis. However, the augmin gene disruptants did not exhibit growth defects under normal, checkpoint-deficient, or MT-destabilised conditions. Moreover, we obtained no evidence that A. nidulans augmin plays a role in γ-tubulin recruitment or in mitotic cell division. Our study uncovered the conservation of the augmin complex in the fungal species, and further suggests that augmin has several functions, besides mitotic spindle MT nucleation, that are yet to be identified.
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Affiliation(s)
- Tomoya Edzuka
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Japan
| | - Lixy Yamada
- Sugashima Marine Biological Laboratory, Graduate School of Science, Nagoya University, Sugashima, Toba, Japan
| | - Kyoko Kanamaru
- Department of Biological Mechanisms and Functions, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Japan
| | - Hitoshi Sawada
- Sugashima Marine Biological Laboratory, Graduate School of Science, Nagoya University, Sugashima, Toba, Japan
| | - Gohta Goshima
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Japan
- * E-mail:
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Govindaraghavan M, McGuire Anglin SL, Shen KF, Shukla N, De Souza CP, Osmani SA. Identification of interphase functions for the NIMA kinase involving microtubules and the ESCRT pathway. PLoS Genet 2014; 10:e1004248. [PMID: 24675878 PMCID: PMC3967960 DOI: 10.1371/journal.pgen.1004248] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Accepted: 02/03/2014] [Indexed: 12/11/2022] Open
Abstract
The Never in Mitosis A (NIMA) kinase (the founding member of the Nek family of kinases) has been considered a mitotic specific kinase with nuclear restricted roles in the model fungus Aspergillus nidulans. By extending to A. nidulans the results of a synthetic lethal screen performed in Saccharomyces cerevisiae using the NIMA ortholog KIN3, we identified a conserved genetic interaction between nimA and genes encoding proteins of the Endosomal Sorting Complex Required for Transport (ESCRT) pathway. Absence of ESCRT pathway functions in combination with partial NIMA function causes enhanced cell growth defects, including an inability to maintain a single polarized dominant cell tip. These genetic insights suggest NIMA potentially has interphase functions in addition to its established mitotic functions at nuclei. We therefore generated endogenously GFP-tagged NIMA (NIMA-GFP) which was fully functional to follow its interphase locations using live cell spinning disc 4D confocal microscopy. During interphase some NIMA-GFP locates to the tips of rapidly growing cells and, when expressed ectopically, also locates to the tips of cytoplasmic microtubules, suggestive of non-nuclear interphase functions. In support of this, perturbation of NIMA function either by ectopic overexpression or through partial inactivation results in marked cell tip growth defects with excess NIMA-GFP promoting multiple growing cell tips. Ectopic NIMA-GFP was found to locate to the plus ends of microtubules in an EB1 dependent manner, while impairing NIMA function altered the dynamic localization of EB1 and the cytoplasmic microtubule network. Together, our genetic and cell biological analyses reveal novel non-nuclear interphase functions for NIMA involving microtubules and the ESCRT pathway for normal polarized fungal cell tip growth. These insights extend the roles of NIMA both spatially and temporally and indicate that this conserved protein kinase could help integrate cell cycle progression with polarized cell growth.
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Affiliation(s)
- Meera Govindaraghavan
- Molecular, Cellular and Developmental Biology Program, The Ohio State University, Columbus, Ohio, United States of America
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | | | - Kuo-Fang Shen
- Molecular, Cellular and Developmental Biology Program, The Ohio State University, Columbus, Ohio, United States of America
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - Nandini Shukla
- Molecular, Cellular and Developmental Biology Program, The Ohio State University, Columbus, Ohio, United States of America
- Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio, United States of America
| | - Colin P. De Souza
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - Stephen A. Osmani
- Molecular, Cellular and Developmental Biology Program, The Ohio State University, Columbus, Ohio, United States of America
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
- Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio, United States of America
- * E-mail:
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De Souza CP, Hashmi SB, Osmani AH, Osmani SA. Application of a new dual localization-affinity purification tag reveals novel aspects of protein kinase biology in Aspergillus nidulans. PLoS One 2014; 9:e90911. [PMID: 24599037 PMCID: PMC3944740 DOI: 10.1371/journal.pone.0090911] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 02/04/2014] [Indexed: 12/22/2022] Open
Abstract
Filamentous fungi occupy critical environmental niches and have numerous beneficial industrial applications but devastating effects as pathogens and agents of food spoilage. As regulators of essentially all biological processes protein kinases have been intensively studied but how they regulate the often unique biology of filamentous fungi is not completely understood. Significant understanding of filamentous fungal biology has come from the study of the model organism Aspergillus nidulans using a combination of molecular genetics, biochemistry, cell biology and genomic approaches. Here we describe dual localization-affinity purification (DLAP) tags enabling endogenous N or C-terminal protein tagging for localization and biochemical studies in A. nidulans. To establish DLAP tag utility we endogenously tagged 17 protein kinases for analysis by live cell imaging and affinity purification. Proteomic analysis of purifications by mass spectrometry confirmed association of the CotA and NimXCdk1 kinases with known binding partners and verified a predicted interaction of the SldABub1/R1 spindle assembly checkpoint kinase with SldBBub3. We demonstrate that the single TOR kinase of A. nidulans locates to vacuoles and vesicles, suggesting that the function of endomembranes as major TOR cellular hubs is conserved in filamentous fungi. Comparative analysis revealed 7 kinases with mitotic specific locations including An-Cdc7 which unexpectedly located to mitotic spindle pole bodies (SPBs), the first such localization described for this family of DNA replication kinases. We show that the SepH septation kinase locates to SPBs specifically in the basal region of apical cells in a biphasic manner during mitosis and again during septation. This results in gradients of SepH between G1 SPBs which shift along hyphae as each septum forms. We propose that SepH regulates the septation initiation network (SIN) specifically at SPBs in the basal region of G1 cells and that localized gradients of SIN activity promote asymmetric septation.
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Affiliation(s)
- Colin P. De Souza
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - Shahr B. Hashmi
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - Aysha H. Osmani
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - Stephen A. Osmani
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
- * E-mail:
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Shen KF, Osmani AH, Govindaraghavan M, Osmani SA. Mitotic regulation of fungal cell-to-cell connectivity through septal pores involves the NIMA kinase. Mol Biol Cell 2014; 25:763-75. [PMID: 24451264 PMCID: PMC3952847 DOI: 10.1091/mbc.e13-12-0718] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Septal pores—the intercellular bridges of fungi—are open during interphase but closed at mitosis. The NIMA kinase mitotically regulates septal pore closing and opening potentially via mechanisms analogous to how it regulates mitotic nuclear pores. The findings explain how and why physically connected Aspergillus cells can maintain mitotic autonomy. Intercellular bridges are a conserved feature of multicellular organisms. In multicellular fungi, cells are connected directly via intercellular bridges called septal pores. Using Aspergillus nidulans, we demonstrate for the first time that septal pores are regulated to be opened during interphase but closed during mitosis. Septal pore–associated proteins display dynamic cell cycle–regulated locations at mature septa. Of importance, the mitotic NIMA kinase locates to forming septa and surprisingly then remains at septa throughout interphase. However, during mitosis, when NIMA transiently locates to nuclei to promote mitosis, its levels at septa drop. A model is proposed in which NIMA helps keep septal pores open during interphase and then closed when it is removed from them during mitosis. In support of this hypothesis, NIMA inactivation is shown to promote interphase septal pore closing. Because NIMA triggers nuclear pore complex opening during mitosis, our findings suggest that common cell cycle regulatory mechanisms might control septal pores and nuclear pores such that they are opened and closed out of phase to each other during cell cycle progression. The study provides insights into how and why cytoplasmically connected Aspergillus cells maintain mitotic autonomy.
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Affiliation(s)
- Kuo-Fang Shen
- Department of Molecular Genetics and Molecular, Cellular and Developmental Biology Program, Ohio State University, Columbus, OH 43210
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Insights into dynamic mitotic chromatin organization through the NIMA kinase suppressor SonC, a chromatin-associated protein involved in the DNA damage response. Genetics 2013; 196:177-95. [PMID: 24214344 DOI: 10.1534/genetics.113.156745] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The nuclear pore complex proteins SonA and SonB, the orthologs of mammalian RAE1 and NUP98, respectively, were identified in Aspergillus nidulans as cold-sensitive suppressors of a temperature-sensitive allele of the essential mitotic NIMA kinase (nimA1). Subsequent analyses found that sonB1 mutants exhibit temperature-dependent DNA damage sensitivity. To understand this pathway further, we performed a genetic screen to isolate additional conditional DNA damage-sensitive suppressors of nimA1. We identified two new alleles of SonA and four intragenic nimA mutations that suppress the temperature sensitivity of the nimA1 mutant. In addition, we identified SonC, a previously unstudied binuclear zinc cluster protein involved with NIMA and the DNA damage response. Like sonA and sonB, sonC is an essential gene. SonC localizes to nuclei and partially disperses during mitosis. When the nucleolar organizer region (NOR) undergoes mitotic condensation and removal from the nucleolus, nuclear SonC and histone H1 localize in a mutually exclusive manner with H1 being removed from the NOR region and SonC being absent from the end of the chromosome beyond the NOR. This region of chromatin is adjacent to a cluster of nuclear pore complexes to which NIMA localizes last during its progression around the nuclear envelope during initiation of mitosis. The results genetically extend the NIMA regulatory system to include a protein with selective large-scale chromatin location observed during mitosis. The data suggest a model in which NIMA and SonC, its new chromatin-associated suppressor, might help to orchestrate global chromatin states during mitosis and the DNA damage response.
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Ludueña RF. A Hypothesis on the Origin and Evolution of Tubulin. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 302:41-185. [DOI: 10.1016/b978-0-12-407699-0.00002-9] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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26
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Qiu R, Zhang J, Xiang X. Identification of a novel site in the tail of dynein heavy chain important for dynein function in vivo. J Biol Chem 2012; 288:2271-80. [PMID: 23212922 DOI: 10.1074/jbc.m112.412403] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The minus end-directed microtubule motor cytoplasmic dynein is responsible for the intracellular movements of many organelles, including nuclei and endosomes. The dynein heavy chain contains a C-terminal motor domain and an N-terminal tail domain. The tail binds other dynein subunits and the cargo-interacting dynactin complex but is dispensable for movement of single dynein molecules in vitro. Here, we identified a mutation in the Aspergillus nidulans heavy chain tail domain, nudA(F208V), which causes obvious defects in dynein-mediated nuclear positioning and early endosome movement. Astonishingly, the nudA(F208I) mutation in the same position does not cause the same defects, suggesting that a subtle difference in the size of the amino acid side chain at this position has a significant consequence. Importantly, our biochemical analyses indicate that the nudA(F208V) mutation does not affect dynein subunit interactions and the mutant dynein is also able to bind dynactin and another dynein regulator, NUDF/LIS1. The mutant dynein is able to physically interact with the early endosome cargo, but dynein-mediated early endosome movement away from the hyphal tip occurs at a significantly reduced frequency. Within the small group of early endosomes that move away from the hyphal tip in the mutant, the average speed of movement is lower than that in the wild type. Given the dispensability of the dynein tail in dynein motility in vitro, our results support the notion that the structural integrity of the dynein tail is critical in vivo for the coordination of dynein force production and movement when the motor is heavily loaded.
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Affiliation(s)
- Rongde Qiu
- Department of Biochemistry and Molecular Biology, the Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA
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Edgerton-Morgan H, Oakley BR. γ-Tubulin plays a key role in inactivating APC/C(Cdh1) at the G(1)-S boundary. ACTA ACUST UNITED AC 2012; 198:785-91. [PMID: 22927465 PMCID: PMC3432763 DOI: 10.1083/jcb.201203115] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Failure to inactivate APC/CCdhA at the G1–S boundary of the cell cycle as a result of a γ-tubulin mutation that disrupts the APC/CCdhA localization prevents cell cycle progression. A γ-tubulin mutation in Aspergillus nidulans, mipA-D159, causes failure of inactivation of the anaphase-promoting complex/cyclosome (APC/C) in interphase, resulting in failure of cyclin B (CB) accumulation and removal of nuclei from the cell cycle. We have investigated the role of CdhA, the A. nidulans homologue of the APC/C activator protein Cdh1, in γ-tubulin–dependent inactivation of the APC/C. CdhA was not essential, but it targeted CB for destruction in G1, and APC/CCdhA had to be inactivated for the G1–S transition. mipA-D159 altered the localization pattern of CdhA, and deletion of the gene encoding CdhA allowed CB to accumulate in all nuclei in strains carrying mipA-D159. These data indicate that mipA-D159 causes a failure of inactivation of APC/CCdhA at G1–S, perhaps by altering its localization to the spindle pole body, and, thus, that γ-tubulin plays an important role in inactivating APC/CCdhA at this point in the cell cycle.
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28
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Habermann K, Lange BM. New insights into subcomplex assembly and modifications of centrosomal proteins. Cell Div 2012; 7:17. [PMID: 22800182 PMCID: PMC3479078 DOI: 10.1186/1747-1028-7-17] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 07/04/2012] [Indexed: 12/19/2022] Open
Abstract
This review provides a brief overview of the recent work on centrosome proteomics, protein complex identification and functional characterization with an emphasis on the literature of the last three years. Proteomics, genetic screens and comparative genomics studies in different model organisms have almost exhaustively identified the molecular components of the centrosome. However, much knowledge is still missing on the protein-protein interactions, protein modifications and molecular changes the centrosome undergoes throughout the cell cycle and development. The dynamic nature of this large multi-protein complex is reflected in the variety of annotated subcellular locations and biological processes of its proposed components. Some centrosomal proteins and complexes have been studied intensively in different organisms and provided detailed insight into centrosome functions. For example, the molecular, structural and functional characterization of the γ-Tubulin ring complex (γ-TuRC) and the the discovery of the Augmin/HAUS complex has advanced our understanding of microtubule (MT) capture, nucleation and organization. Surprising findings revealed new functions and localizations of proteins that were previously regarded as bona fide centriolar or centrosome components, e.g. at the kinetochore or in the nuclear pore complex regulating MT plus end capture or mRNA processing. Many centrosome components undergo posttranslational modifications such as phosphorylation, SUMOylation and ubiquitylation that are critical in modulating centrosome function and biology. A wealth of information has recently become available driven by new developments in technologies such as mass spectrometry, light and electron microscopy providing more detailed molecular and structural definition of the centrosome and particular roles of proteins throughout the cell cycle and development.
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Affiliation(s)
- Karin Habermann
- Department of Vertebrate Genomics, Max Planck Institute for Molecular Genetics, Berlin, Germany.
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29
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Tipton AR, Wang K, Oladimeji P, Sufi S, Gu Z, Liu ST. Identification of novel mitosis regulators through data mining with human centromere/kinetochore proteins as group queries. BMC Cell Biol 2012; 13:15. [PMID: 22712476 PMCID: PMC3419070 DOI: 10.1186/1471-2121-13-15] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Accepted: 06/19/2012] [Indexed: 01/14/2023] Open
Abstract
Background Proteins functioning in the same biological pathway tend to be transcriptionally co-regulated or form protein-protein interactions (PPI). Multiple spatially and temporally regulated events are coordinated during mitosis to achieve faithful chromosome segregation. The molecular players participating in mitosis regulation are still being unravelled experimentally or using in silico methods. Results An extensive literature review has led to a compilation of 196 human centromere/kinetochore proteins, all with experimental evidence supporting the subcellular localization. Sixty-four were designated as “core” centromere/kinetochore components based on peak expression and/or well-characterized functions during mitosis. By interrogating and integrating online resources, we have mined for genes/proteins that display transcriptional co-expression or PPI with the core centromere/kinetochore components. Top-ranked hubs in either co-expression or PPI network are not only enriched with known mitosis regulators, but also contain candidates whose mitotic functions are not yet established. Experimental validation found that KIAA1377 is a novel centrosomal protein that also associates with microtubules and midbody; while TRIP13 is a novel kinetochore protein and directly interacts with mitotic checkpoint silencing protein p31comet. Conclusions Transcriptional co-expression and PPI network analyses with known human centromere/kinetochore proteins as a query group help identify novel potential mitosis regulators.
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Affiliation(s)
- Aaron R Tipton
- Department of Biological Sciences, University of Toledo, Toledo, OH 43606, USA
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30
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Egan MJ, Tan K, Reck-Peterson SL. Lis1 is an initiation factor for dynein-driven organelle transport. ACTA ACUST UNITED AC 2012; 197:971-82. [PMID: 22711696 PMCID: PMC3384415 DOI: 10.1083/jcb.201112101] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
The dynein-associated protein Lis1 may be a ubiquitous determinant of dynein-dependent transport required primarily at the stage of motility initiation. The molecular motor cytoplasmic dynein is responsible for most minus-end–directed, microtubule-based transport in eukaryotic cells. It is especially important in neurons, where defects in microtubule-based motility have been linked to neurological diseases. For example, lissencephaly is caused by mutations in the dynein-associated protein Lis1. In this paper, using the long, highly polarized hyphae of the filamentous fungus Aspergillus nidulans, we show that three morphologically and functionally distinct dynein cargos showed transport defects in the genetic absence of Lis1/nudF, raising the possibility that Lis1 is ubiquitously used for dynein-based transport. Surprisingly, both dynein and its cargo moved at normal speeds in the absence of Lis1 but with reduced frequency. Moreover, Lis1, unlike dynein and dynactin, was absent from moving dynein cargos, further suggesting that Lis1 is not required for dynein-based cargo motility once it has commenced. Based on these observations, we propose that Lis1 has a general role in initiating dynein-driven motility.
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Affiliation(s)
- Martin J Egan
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
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31
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γ-Tubulin 2 nucleates microtubules and is downregulated in mouse early embryogenesis. PLoS One 2012; 7:e29919. [PMID: 22235350 PMCID: PMC3250491 DOI: 10.1371/journal.pone.0029919] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Accepted: 12/06/2011] [Indexed: 01/09/2023] Open
Abstract
γ-Tubulin is the key protein for microtubule nucleation. Duplication of the γ-tubulin gene occurred several times during evolution, and in mammals γ-tubulin genes encode proteins which share ∼97% sequence identity. Previous analysis of Tubg1 and Tubg2 knock-out mice has suggested that γ-tubulins are not functionally equivalent. Tubg1 knock-out mice died at the blastocyst stage, whereas Tubg2 knock-out mice developed normally and were fertile. It was proposed that γ-tubulin 1 represents ubiquitous γ-tubulin, while γ-tubulin 2 may have some specific functions and cannot substitute for γ-tubulin 1 deficiency in blastocysts. The molecular basis of the suggested functional difference between γ-tubulins remains unknown. Here we show that exogenous γ-tubulin 2 is targeted to centrosomes and interacts with γ-tubulin complex proteins 2 and 4. Depletion of γ-tubulin 1 by RNAi in U2OS cells causes impaired microtubule nucleation and metaphase arrest. Wild-type phenotype in γ-tubulin 1-depleted cells is restored by expression of exogenous mouse or human γ-tubulin 2. Further, we show at both mRNA and protein levels using RT-qPCR and 2D-PAGE, respectively, that in contrast to Tubg1, the Tubg2 expression is dramatically reduced in mouse blastocysts. This indicates that γ-tubulin 2 cannot rescue γ-tubulin 1 deficiency in knock-out blastocysts, owing to its very low amount. The combined data suggest that γ-tubulin 2 is able to nucleate microtubules and substitute for γ-tubulin 1. We propose that mammalian γ-tubulins are functionally redundant with respect to the nucleation activity.
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Hubert T, Vandekerckhove J, Gettemans J. Cdk1 and BRCA1 target γ-tubulin to microtubule domains. Biochem Biophys Res Commun 2011; 414:240-5. [PMID: 21951856 DOI: 10.1016/j.bbrc.2011.09.064] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2011] [Accepted: 09/13/2011] [Indexed: 01/01/2023]
Abstract
DNA damage is a critical event that requires an appropriate cellular response. This is mediated by checkpoint proteins such as Cdk1 that controls S/G2 and G2/M transition. Cdk1 is required for BRCA1 transport to DNA damage sites inside the nucleus where BRCA1 functions as a scaffold to initiate a signaling cascade. BRCA1 is a multifunctional protein that also ubiquitinates γ-tubulin and, consequently, inhibits microtubule nucleation at the centrosome. Here, we report that γ-tubulin also localizes at confined areas in the microtubule network. Nocodazole-mediated microtubule depolymeration results in disappearance of this γ-tubulin fraction, while microtubule stabilization by taxol preserves this structure. Surprisingly, overexpression of Cdk1 or BRCA1 greatly expands the γ-tubulin coating of microtubules, suggesting that the microtubule-bound γ-tubulin is involved in DNA damage response. This is in accordance with numerous reports of microtubule-associated DNA damage proteins, such as p53, that are transported to the nucleus when DNA damage occurs. γ-Tubulin itself has been reported to form complexes with DNA repair proteins in the nucleus.
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Affiliation(s)
- Thomas Hubert
- Department of Medical Protein Research, VIB, B-9000 Ghent, Belgium
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Balbi A, Anzaldi M, Macciò C, Aiello C, Mazzei M, Gangemi R, Castagnola P, Miele M, Rosano C, Viale M. Synthesis and biological evaluation of novel pyrazole derivatives with anticancer activity. Eur J Med Chem 2011; 46:5293-309. [PMID: 21920636 DOI: 10.1016/j.ejmech.2011.08.014] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 07/19/2011] [Accepted: 08/09/2011] [Indexed: 11/24/2022]
Abstract
We synthesized thirty-six novel pyrazole derivatives and studied their antiproliferative activity in human ovarian adenocarcinoma A2780 cells, human lung carcinoma A549 cells, and murine P388 leukemia cells. Four of these substances were selected because of their higher antiproliferative activity and further analyses showed that they were all able to induce apoptosis, although to a different extent. The expression of p53 and p21(waf1), which induce apoptosis and cell cycle arrest, was evaluated by western blot analysis in cells treated with compound 12d. The analysis of the cell cycle showed that all the selected compounds cause a partial G2/M block and the formation of polyploid cells. Furthermore, the four selected compounds were tested for their interaction with the microtubular cytoskeletal system by docking analysis, tubulin polymerization assay and immunofluorescence staining, demonstrating that the compound 12d, unlike the other active derivatives, was able to significantly bind dimers of α- and β-tubulin, probably causing a molecular distortion resulting in the disassembly of microtubules.
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Affiliation(s)
- Alessandro Balbi
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Genova, V.le Benedetto XV 3, 16132 Genova, Italy.
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34
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Regulated inactivation of the spindle assembly checkpoint without functional mitotic spindles. EMBO J 2011; 30:2648-61. [PMID: 21642954 DOI: 10.1038/emboj.2011.176] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Accepted: 05/09/2011] [Indexed: 12/13/2022] Open
Abstract
The spindle assembly checkpoint (SAC) arrests mitosis until bipolar attachment of spindle microtubules to all chromosomes is accomplished. However, when spindle formation is prevented and the SAC cannot be satisfied, mammalian cells can eventually overcome the mitotic arrest while the checkpoint is still activated. We find that Aspergillus nidulans cells, which are unable to satisfy the SAC, inactivate the checkpoint after a defined period of mitotic arrest. Such SAC inactivation allows normal nuclear reassembly and mitotic exit without DNA segregation. We demonstrate that the mechanisms, which govern such SAC inactivation, require protein synthesis and can occur independently of inactivation of the major mitotic regulator Cdk1/Cyclin B or mitotic exit. Moreover, in the continued absence of spindle function cells transit multiple cell cycles in which the SAC is reactivated each mitosis before again being inactivated. Such cyclic activation and inactivation of the SAC suggests that it is subject to cell-cycle regulation that is independent of bipolar spindle function.
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35
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In Brief. Nat Rev Mol Cell Biol 2010. [DOI: 10.1038/nrm2967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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36
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Short B. γ-Tubulin keeps the cell cycling. J Biophys Biochem Cytol 2010. [PMCID: PMC2922651 DOI: 10.1083/jcb.1903iti1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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