Integrating Complex Functions: Coordination of Nuclear Pore Complex Assembly and Membrane Expansion of the Nuclear Envelope Requires a Family of Integral Membrane Proteins PDF Download
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Languages : en
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The nuclear envelope harbors numerous large proteinaceous channels, the nuclear pore complexes (NPCs), through which macromolecular exchange between the cytosol and the nucleoplasm occurs. This double-membrane nuclear envelope is continuous with the endoplasmic reticulum and thus functionally connected to such diverse processes as vesicular transport, protein maturation and lipid synthesis. Recent results obtained from studies in Saccharomyces cerevisiae indicate that assembly of the nuclear pore complex is functionally dependent upon maintenance of lipid homeostasis of the ER membrane. Previous work from one of our laboratories has revealed that an integral membrane protein Apq12 is important for the assembly of functional nuclear pores. Cells lacking APQ12 are viable but cannot grow at low temperatures, have aberrant NPCs and a defect in mRNA export. Remarkably, these defects in NPC assembly can be overcome by supplementing cells with a membrane fluidizing agent, benzyl alcohol, suggesting that Apq12 impacts the flexibility of the nuclear membrane, possibly by adjusting its lipid composition when cells are shifted to a reduced temperature. Our new study now expands these findings and reveals that an essential membrane protein, Brr6, shares at least partially overlapping functions with Apq12 and is also required for assembly of functional NPCs. A third nuclear envelope membrane protein, Brl1, is related to Brr6, and is also required for NPC assembly. Because maintenance of membrane homeostasis is essential for cellular survival, the fact that these three proteins are conserved in fungi that undergo closed mitoses, but are not found in metazoans or plants, may indicate that their functions are performed by proteins unrelated at the primary sequence level to Brr6, Brl1 and Apq12 in cells that disassemble their nuclear envelopes during mitosis.
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Languages : en
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Book Description
The nuclear envelope harbors numerous large proteinaceous channels, the nuclear pore complexes (NPCs), through which macromolecular exchange between the cytosol and the nucleoplasm occurs. This double-membrane nuclear envelope is continuous with the endoplasmic reticulum and thus functionally connected to such diverse processes as vesicular transport, protein maturation and lipid synthesis. Recent results obtained from studies in Saccharomyces cerevisiae indicate that assembly of the nuclear pore complex is functionally dependent upon maintenance of lipid homeostasis of the ER membrane. Previous work from one of our laboratories has revealed that an integral membrane protein Apq12 is important for the assembly of functional nuclear pores. Cells lacking APQ12 are viable but cannot grow at low temperatures, have aberrant NPCs and a defect in mRNA export. Remarkably, these defects in NPC assembly can be overcome by supplementing cells with a membrane fluidizing agent, benzyl alcohol, suggesting that Apq12 impacts the flexibility of the nuclear membrane, possibly by adjusting its lipid composition when cells are shifted to a reduced temperature. Our new study now expands these findings and reveals that an essential membrane protein, Brr6, shares at least partially overlapping functions with Apq12 and is also required for assembly of functional NPCs. A third nuclear envelope membrane protein, Brl1, is related to Brr6, and is also required for NPC assembly. Because maintenance of membrane homeostasis is essential for cellular survival, the fact that these three proteins are conserved in fungi that undergo closed mitoses, but are not found in metazoans or plants, may indicate that their functions are performed by proteins unrelated at the primary sequence level to Brr6, Brl1 and Apq12 in cells that disassemble their nuclear envelopes during mitosis.
Author: Alexis Spain Madrid
Publisher:
ISBN:
Category :
Languages : en
Pages : 240
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Author: Daniel James Anderson
Publisher:
ISBN:
Category :
Languages : en
Pages : 145
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The nucleus is in many ways the centerpiece of the eukaryotic cell, as it houses the genome and is the primary site of gene regulation. Nuclear enclosure is achieved by the double lipid bilayer named the nuclear envelope (NE). The outer membrane of the NE is connected and continuous with the endoplasmic reticulum (ER). The inner membrane of the NE attaches to chromatin and a meshwork of intermediate filaments called the nuclear lamina though NE-specific integral membrane proteins. Transport between the cytoplasm and nucleoplasm is mediated by nuclear pore complexes, multi-protein assemblies that are present where of the NE where the outer and inner membranes are connected. In metazoans, the nuclear envelope is broken down during mitosis to allow for cytoplasm spindle formation and segregation the NE materials into the daughter cells. At the beginning of my thesis the fate of NE components during cell division and the mechanism of nuclear reformation have been controversial, and it was unclear whether the NE is broken into vesicles or absorbed into the ER during mitosis. The main focus of this thesis was to characterize NE formation at the end of open mitosis. We determine that the network of ER tubules directly contributes to nuclear membrane formation in a fusion independent mechanism. A role for the ER shaping protein family of Reticulons as a negative regulator of NE formation was also characterized. A model was developed where transmembrane proteins of the NE target and reshape ER membranes around chromatin during nuclear assembly. This model was supported be a detailed kinetic analysis of nuclear assembly in cells where protein expression levels of candidate proteins were changed. Together these studies clarify the mechanism of how the nuclear membrane encloses the chromatin mass at the end of cell division.
Author:
Publisher: Elsevier
ISBN: 0124171788
Category : Science
Languages : en
Pages : 553
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Book Description
Volume 122 of Methods in Cell Biology describes modern tools and techniques used to study nuclear pore complexes and nucleocytoplasmic transport in diverse eukaryotic model systems (including mammalian cells, Xenopus, C. elegans, yeast). The volume enables investigators to analyze nuclear pore complex structure, assembly, and dynamics; to evaluate protein and RNA trafficking through the nuclear envelope; and to design in vivo or in vitro assays appropriate to their research needs. Beyond the study of nuclear pores and transport as such, these protocols will also be helpful to scientists characterizing gene regulation, signal transduction, cell cycle, viral infections, or aging. The NPC being one of the largest multiprotein complexes in the cell, some protocols will also be of interest for people currently characterizing other macromolecular assemblies. This book is thus designed for laboratory use by graduate students, technicians, and researchers in many molecular and cellular disciplines. Describes modern tools and techniques used to study nuclear pore complexes and nucleocytoplasmic transport in diverse eukaryotic model systems (mammalian cells, Xenopus, C. elegans, yeast) Chapters are written by experts in the field Cutting-edge material
Author: Jeffrey S. Smith
Publisher: Humana
ISBN: 9781493951826
Category : Science
Languages : en
Pages : 0
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Book Description
Yeast Genetics: Methods and Protocols is a collection of methods to best study and manipulate Saccharomyces cerevisiae, a truly genetic powerhouse. The simple nature of a single cell eukaryotic organism, the relative ease of manipulating its genome and the ability to interchangeably exist in both haploid and diploid states have always made it an attractive model organism. Genes can be deleted, mutated, engineered and tagged at will. Saccharomyces cerevisiae has played a major role in the elucidation of multiple conserved cellular processes including MAP kinase signaling, splicing, transcription and many others. Written in the successful Methods in Molecular Biology series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible protocols and notes on troubleshooting and avoiding known pitfalls. Authoritative and easily accessible, Yeast Genetics: Methods and Protocols will provide a balanced blend of classic and more modern genetic methods relevant to a wide range of research areas and should be widely used as a reference in yeast labs.
Author: Gregg G. Gundersen
Publisher:
ISBN: 9781493986910
Category : Cytoskeleton
Languages : en
Pages : 338
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Author: Maximiliano D’Angelo
Publisher: Springer
ISBN: 331971614X
Category : Medical
Languages : en
Pages : 245
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Book Description
The three-dimensional organization of the DNA inside the eukaryotic cell nucleus has emerged a critical regulator of genome integrity and function. Increasing evidence indicates that nuclear pore complexes (NPCs), the large protein channels that connect the nucleus to the cytoplasm, play a critical role in the establishment and maintenance of chromatin organization and in the regulation of gene activity. These findings, which oppose the traditional view of NPCs as channels with only one: the facilitation of nucleocytoplasmic molecule exchange, have completely transformed our understanding of these structures. This book describes our current knowledge of the role of NPCs in genome organization and gene expression regulation. It starts by providing an overview of the different compartments and structures of the nucleus and how they contribute to organizing the genome, then moves to examine the direct roles of NPCs and their components in gene expression regulation in different organisms, and ends by describing the function of nuclear pores in the infection and genome integration of HIV, in DNA repair and telomere maintenance, and in the regulation of chromosome segregation and mitosis. This book provides an intellectual backdrop for anyone interested in understanding how the gatekeepers of the nucleus contribute to safeguarding the integrity and function of the eukaryotic genome.
Author: David Evans
Publisher: Taylor & Francis
ISBN: 1134279825
Category : Science
Languages : en
Pages : 519
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Book Description
The Nuclear Envelope brings together the major current topics in nuclear envelope structure, transport, transcriptional regulation and cell signaling. The volume is divided into four sections: 1. Proteins of the nuclear envelope, including nuclear envelope proteomics, structure and function. 2. Nuclear pores and transport at the nuclear envelope, including pore complex structure, assembly and function and import and export pathways. 3. Nuclear envelope dynamics, including dynamics of lamina assembly and disassembly. 4. Nuclear signaling and transcription regulation, including signaling to the nucleus and spectrin repeat proteins and their implications or communication between the nucleus and cytoplasm.
Author: Sue Shackleton
Publisher: Humana
ISBN: 9781493935284
Category : Science
Languages : en
Pages : 0
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Book Description
This volume provides a wide range of protocols used in studying the nuclear envelope, with special attention to the experimental adjustments that may be required to successfully investigate this complex organelle in cells from various organisms. The Nuclear Envelope: Methods and Protocols is divided into five sections: Part I – Nuclear Envelope Isolation; Part II – Nuclear Envelope Protein Interactions, Localization, and Dynamics; Part III – Nuclear Envelope Interactions with the Cytoskeleton; Part IV – Nuclear Envelope-Chromatin Interactions; and Part V – Nucleo-Cytoplasmic Transport. Many of the modifications discussed in this book have only been circulated within laboratories that have conducted research in this field for many years. Written in the highly successful Methods in Molecular Biology series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible laboratory protocols, and tips on troubleshooting and avoiding known pitfalls. Cutting edge and thorough, The Nuclear Envelope: Methods and Protocols is a timely resource for researchers who have joined this dynamic and rapidly growing field.
Author: Beth A. Rasala
Publisher:
ISBN: 9780549423874
Category :
Languages : en
Pages : 241
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Book Description
My thesis is focused upon molecularly defining the mechanism of early steps in metazoan nuclear pore assembly. Nuclear pore complexes (NPCs) are large proteinaceous structures that span the nuclear envelope and act as gated aqueous channels to regulate the transport of macromolecules between the nucleus and cytoplasm. In metazoans, the massive NPCs disassemble into soluble subunits at the beginning of mitosis and then somehow reassemble following chromosome segregation; a process that is coordinated with membrane recruitment and fusion. The mechanism and order of NPC assembly is poorly understood. In Chapter 1, I show that ELYS co-purifies with the Nup107-160 complex, the largest subunit of the NPC, in Xenopus egg and human cell extracts. Indeed, I demonstrate that ELYS is a dual nucleoporin/kinetochore protein required for nuclear pore assembly and proper cell division. In Chapter 2, I focus on defining the early steps in nuclear pore assembly, including the mechanism for ELYS as the pore 'targeting' protein. In Chapter 3, I collaborated with Dr. Corinne Ramos on a study to order pore assembly with respect to inner and outer nuclear membrane fusion. Taken the data from chapters 1-3 together, I suggest a model in which NPC assembly is initiated on AT-rich chromatin through an interaction with the C-terminus of ELYS. The data also show the chromatin binding of ELYS precedes and is required for the binding of the Nup107-160 complex. Chromatin-bound ELYS and the Nup107-160 complex then recruit integral pore membrane proteins POM121- and NDC1-containing membrane vesicles. Membrane vesicle fusion takes place to form patches of continuous double nuclear membranes. Oligomerization of ELYS/Nup107-160/POM121 then acts to promote fusion between the inner and outer nuclear membranes to form a diffusion channel. Finally, the remaining soluble pore subunits are recruited to assemble the mature, functional nuclear pore. Finally, Appendix B presents data on the Xenopus binding partners of the C-terminus of Nup160, a member of the Nup107-160 complex, which was derived from mass spectrometry analyses. This data led to the discovery that vertebrate centrin 2 localizes to NPCs and functions in mRNA and protein export, as described in Chapter 4.
