What is Nup358?
Abstract. In vertebrate cells, the nucleoporin Nup358/RanBP2 is a major component of the filaments that emanate from the nuclear pore complex into the cytoplasm. Nup358 forms a complex with SUMOylated RanGAP1, the GTPase activating protein for Ran.
What is the function of ran gap in relation to nuclear import and export?
Ran GTPase Cycle Participates in Nuclear Envelope Assembly The interaction of RanGTP with importin-beta complexes causes their local release and assembly into nuclear pore complexes (NPCs), the fusion of vesicles to form a double membrane, and the restarting of nuclear transport.
How does nuclear import occur?
The import of nuclear proteins through the pore complex concentrates specific proteins in the nucleus, thereby increasing order in the cell, which must consume energy (discussed in Chapter 2). The energy is thought to be provided by the hydrolysis of GTP by the monomeric GTPase Ran.
What is the role of Ran-GTP in nuclear transport?
To summarize, RanGTPase plays a role in the nuclear export in such a way that nuclear GTP-bound Ran triggers the aggregation of Ran:exportin:cargo trimeric complex which is then transported to cytoplasm while hydrolysis of RanGTP to RanGDP releases the export cargoes in cytoplasm.
What is Ran GDP?
The Ran (Ran-related or Ras-like nuclear) protein is the single member of the Ran subfamily, and the most abundant small GTPase in the cell. Like the other small GTPases, Ran functions as a molecular switch, converting between the active GTP-bound and inactive GDP-bound conformations.
How is protein imported into nucleus?
Abstract. Nuclear proteins are transported actively through nuclear pores by a selective, mediated process. The process is mediated by a nuclear localization signal (NLS), and can be divided into at least two steps, (a) targeting to the pores and (b) translocation through the pores.
How does importin enter nucleus?
Following binding at the pore complex, proteins are translocated through the pore into the nucleus in a manner requiring ATP. The biochemical dissection of the nuclear pore complex has begun. Alteration of protein import into the nucleus is emerging as a new and complex form of regulation.
How does Ran GTPase regulate protein transport into the nucleus?
Inside the nucleus, the high concentration of Ran-GTP rapidly binds to importin-β to dissociate the complex, releasing the transported protein, followed by recycling of the importins back to the cytoplasm.
How does Ran GDP get into nucleus?
Export carriers bring both Ran–GTP and cargo to the cytoplasm, and presumably recycle back into the nucleus alone. factor called NTF2 (or p10). It binds to Ran–GDP and carries the Ran through the nuclear pores into the nucleus where it is released by RanGEF, which converts Ran to the GTP-bound state.
Is Ran a G protein?
Ran is a small G protein that is essential for the translocation of RNA and proteins through the nuclear pore complex. The Ran protein has also been implicated in the control of DNA synthesis and cell cycle progression, as mutations in Ran have been found to disrupt DNA synthesis.
What type of protein is Ran?
Abstract. Ras related nuclear protein (Ran) is a 25-kDa member of the Ras superfamily of small guanosine triphosphatases (GTPases). To date, a Ran homolog has been found in every nucleated cell of every eukaryotic organism on Earth, and Ran is essential for the viability of all those cells.
How are proteins transported into mitochondria?
Proteins are translocated into the mitochondrial matrix space by passing through the TOM and TIM complexes at sites of adhesion between the outer and inner membranes known as contact sites.
What is importin alpha and beta?
Importin α is known to bind to the nuclear localization signal (NLS) sequence of nucleus targeted proteins. After this recognition, importin α links the protein to importin β, which transports the NLS-containing protein across the nuclear envelope to its destination.
What is the function of importin?
The primary function of importin is to mediate the translocation of proteins with nuclear localization signals into the nucleus, through nuclear pore complexes (NPC), in a process known as the nuclear protein import cycle.
Which GTP binding protein is responsible for moving importin from nucleus to cytosol?
A key player in the translocation process is a small GTP-binding protein called Ran, which is related to the Ras proteins (Figure 8.10).
What is the role of Ran GTPase in nuclear import?
In nuclear import, Ran dissociates importin β:cargo complex in the nucleus and recycles importin β to cytoplasm. In nuclear export, Ran triggers the formation of the export complex and RanGTPase hydrolysis releases the export-cargo in cytoplasm.
Why is Ran-GTP concentrated in the nucleus?
It is concentrated in the nucleus by an active import mechanism where it generates a high concentration of RanGTP by nucleotide exchange. It controls the assembly and disassembly of a range of complexes that are formed between Ran-binding proteins and cellular cargo to maintain rapid nuclear transport.
What is the role of the Ran-GTP protein in nuclear transport?
It is this ran gradient which provides the energy necessary for the transport of proteins into and out of the nucleus by karyopherin proteins.
What is the function of Ran GDP?
Ran-GDP has been shown to shuttle from the cytoplasm to the nucleus, where Ran becomes GTP-bound and active. Ran functions in the regulation nuclear protein import and export.
How is Ran regulated?
Small GTP-binding protein Ran is regulated by posttranslational lysine acetylation.
What is nucleoporin Nup358?
Nup358, a nucleoporin, functions as a key determinant of the nuclear pore complex structure remodeling during skeletal myogenesis The nuclear pore complex (NPC) is the only gateway for molecular trafficking across the nuclear envelope.
Is nup358-ago a new interacting motif for the AGO family of proteins?
Our study indicates that Nup358-AGO interaction is important for miRNA-mediated gene silencing and identifies SIM as a new interacting motif for the AGO family of proteins. The findings also support a model wherein the coupling of miRISC with the target mRNA could occur at AL, specialized domains within the ER, and at the nuclear envelope.
Does Nup358 bind to spindles and kinetochores?
In conclusion, previous studies have shown that Nup358 binds to mitotic spindles and kinetochores, and defined a role for Nup358 during mitosis in mediating proper microtubule-kinetochore interactions [5-8].
Where are the Nup358 puncta colocalized?
Remarkably, the endogenous Nup358 puncta often colocalized with microtubules, particularly at cell extensions (Fig. 1A, arrow). At lower exposure, the nuclear pore localization is distinctly evident (Fig 1A, arrow head).