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What is the main function of the nuclear lamina?
What is the main function of the nuclear lamina?
What is the outer nuclear membrane continuous with?
What is the outer nuclear membrane continuous with?
What is the purpose of the nuclear pore complexes?
What is the purpose of the nuclear pore complexes?
Where are the ribosomes that synthesize proteins in the ER located?
Where are the ribosomes that synthesize proteins in the ER located?
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What is transported into the perinuclear space?
What is transported into the perinuclear space?
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What are the proteins in the inner nuclear membrane part of?
What are the proteins in the inner nuclear membrane part of?
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What is the main function of the nuclear envelope?
What is the main function of the nuclear envelope?
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What is the purpose of the protein complexes that span the nuclear envelope?
What is the purpose of the protein complexes that span the nuclear envelope?
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What is the primary function of a nuclear import receptor?
What is the primary function of a nuclear import receptor?
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What happens to the nuclear localization signal on a cargo protein when it is loaded with a cargo protein?
What happens to the nuclear localization signal on a cargo protein when it is loaded with a cargo protein?
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What is the role of adaptor proteins in nuclear import?
What is the role of adaptor proteins in nuclear import?
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What is the function of the FG repeats in the unstructured domains of nucleoporins?
What is the function of the FG repeats in the unstructured domains of nucleoporins?
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What is the result of the import receptor binding to the FG repeats in the NPC pore?
What is the result of the import receptor binding to the FG repeats in the NPC pore?
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What is the mechanism by which the import receptor accelerates cargo transport into the nucleus?
What is the mechanism by which the import receptor accelerates cargo transport into the nucleus?
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What confers directionality to the nuclear import process?
What confers directionality to the nuclear import process?
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What happens to the import receptor after it has transported cargo into the nucleus?
What happens to the import receptor after it has transported cargo into the nucleus?
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What triggers the disassembly of the nuclear lamina during mitosis?
What triggers the disassembly of the nuclear lamina during mitosis?
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What is a common feature of the breakdown of the nuclear envelope during mitosis in metazoan cells?
What is a common feature of the breakdown of the nuclear envelope during mitosis in metazoan cells?
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What occurs as decondensation of daughter chromosomes progresses?
What occurs as decondensation of daughter chromosomes progresses?
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What is involved in the reassembly process of the nuclear envelope?
What is involved in the reassembly process of the nuclear envelope?
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In which organism does the nuclear envelope remain intact during mitosis?
In which organism does the nuclear envelope remain intact during mitosis?
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What triggers the re-formation of the lamin network around the decondensing daughter chromosomes?
What triggers the re-formation of the lamin network around the decondensing daughter chromosomes?
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In which cellular compartment is Ran GAP located?
In which cellular compartment is Ran GAP located?
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What happens to SREBP when the cholesterol-binding site on SCAP is empty?
What happens to SREBP when the cholesterol-binding site on SCAP is empty?
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Where does the exchange of GDP for GTP occur to convert Ran-GDP to Ran-GTP?
Where does the exchange of GDP for GTP occur to convert Ran-GDP to Ran-GTP?
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What is the result of SREBP binding to the promoters of genes involved in cholesterol biosynthesis?
What is the result of SREBP binding to the promoters of genes involved in cholesterol biosynthesis?
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What is the consequence of low cholesterol concentrations on SCAP?
What is the consequence of low cholesterol concentrations on SCAP?
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Where is SREBP initially synthesized?
Where is SREBP initially synthesized?
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What is the purpose of the regulation of cholesterol biosynthesis through SREBP?
What is the purpose of the regulation of cholesterol biosynthesis through SREBP?
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What is the role of the SCAP-INSIG complex in cholesterol biosynthesis?
What is the role of the SCAP-INSIG complex in cholesterol biosynthesis?
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What is the primary function of FG repeat–binding sites on the surface of nuclear import receptors?
What is the primary function of FG repeat–binding sites on the surface of nuclear import receptors?
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What is the result of the interaction between FG repeats and cargo receptors?
What is the result of the interaction between FG repeats and cargo receptors?
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What determines the directionality of nuclear import and export?
What determines the directionality of nuclear import and export?
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What is the role of Ran GAP in the Ran GTPase cycle?
What is the role of Ran GAP in the Ran GTPase cycle?
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What is the critical difference between Ran-mediated nuclear import and nuclear export?
What is the critical difference between Ran-mediated nuclear import and nuclear export?
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What is the characteristic of Ran GTPase?
What is the characteristic of Ran GTPase?
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What is the result of the interaction between cargo receptors and FG repeats in the NPC?
What is the result of the interaction between cargo receptors and FG repeats in the NPC?
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What is the function of the mesh of FG repeat–containing proteins in the NPC?
What is the function of the mesh of FG repeat–containing proteins in the NPC?
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Study Notes
The Nuclear Envelope
- The nuclear envelope is a double membrane structure penetrated by nuclear pore complexes.
- Transmembrane proteins in the inner and outer nuclear membranes link the nuclear lamina to the cytosolic cytoskeleton.
- The outer nuclear membrane is continuous with the endoplasmic reticulum (ER).
The Lamina
- The lamina provides structural support for the nuclear envelope and acts as an anchoring site for chromosomes and nuclear pore complexes.
- The lamina is connected to the cytoplasmic cytoskeleton via protein complexes that span the nuclear envelope.
Nuclear Pore Complexes
- Nuclear pores conduct extensive bidirectional traffic between the cytosol and the nucleus.
- The many proteins that function in the nucleus are selectively imported into the nuclear compartment from the cytosol.
- These proteins contain a nuclear localization signal that binds them to an import receptor.
Nuclear Import Receptors
- Nuclear localization signals are recognized by nuclear transport receptors (karyopherin family members).
- Each import receptor can bind and transport the subset of cargo proteins containing the appropriate nuclear localization signal.
- Import receptors use adaptor proteins to form a bridge between the import receptors and the nuclear localization signals on the proteins to be transported.
Nuclear Import Mechanism
- Import receptors contain multiple low-affinity binding sites for the FG repeats found in the unstructured domains of several nucleoporins.
- The FG repeats in the fibrils of cytosol-facing nucleoporins serve to initially recruit import receptors and their bound cargo proteins to NPCs.
- The import receptor-cargo complex diffuses into and within the NPC pore, allowing the cargo to traverse the distance across an NPC in a few milliseconds.
Ran GTPase Cycle
- The Ran GTPase cycle provides directionality to both nuclear import and nuclear export.
- The differential localization of Ran-GTP in the nucleus and Ran-GDP in the cytosol provides directionality.
Regulation of Nuclear Transport
- Feedback regulation of cholesterol biosynthesis is an example of how transcription through NPCs can be regulated by controlling access to the transport machinery.
- The breakdown and re-formation of the nuclear envelope and lamina occur during mitosis, with phosphorylation and dephosphorylation of the lamins triggering the disassembly and reassembly of the nuclear lamina.
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Description
Learn about the role of nuclear import receptors and cargo receptors in facilitating nuclear transportation through nuclear pore complexes (NPCs). Understand how FG repeat-binding sites and interactions with cytosolic fibrils enable this process.
