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Nuclear Protein Sorting

Nuclear Protein Sorting

Nuclear protein sorting is the selective trafficking of histones, polymerases, gene regulatory proteins into the nucleus and exporting RNAs and ribosomes to the cytosol. It is a tightly controlled process that regulates gene expression within a cell.
Proteins targeted to the nucleus carry nuclear localization signals or NLS recognized by import receptors in the cytosol. Similarly, proteins with nuclear export signals are recognized by export receptors. Import and export receptors are...

Directionality of Nuclear Transport

Directionality of Nuclear Transport

Ras-related nuclear protein or Ran is a small G protein that cycles between its GTP and GDP bound states. Ran specific regulators, a Ran GTPase Activating Protein or RanGAP present in the cytosol and a Ran guanine nucleotide exchange factor or RanGEF present inside the nucleus regulate GTP/GDP exchange. A high concentration of GTP inside the cells, in addition to this asymmetric distribution of Ran-specific regulators, leads to a higher RanGTP concentration inside the nucleus. This...

Regulation of Nuclear Protein Sorting

Regulation of Nuclear Protein Sorting

Nuclear protein sorting regulates nucleus composition and gene expression, crucial for determining the fate of a eukaryotic cell. Hence, the entry and exit of molecules across the nuclear envelope is a tightly controlled process. Nuclear protein sorting can be inhibited by one of the following ways: 1) masking cargo signal sequences, 2) modifying the nuclear receptor's affinity for cargo, 3) controlling the nuclear pore size, 4) retaining the cargo during its transit to the cytosol or the...

Nuclear Export

Nuclear Export

The nucleus restricts several proteins within and allows others to pass. The restricted proteins possess a nuclear retention sequence or NRS, anchoring them to the nuclear lamins and preventing their transport to the cytosol. The non-restricted proteins, after their synthesis, are transported to their site of action, such as the cytosol or other organelles, with the help of nuclear export signals or NES.
NES are of three types- the canonical 10-residue long leucine-rich signal and other...

Nuclear Export of mRNA

Nuclear Export of mRNA

Before mRNAs are exported to the cytoplasm, it is crucial to check each mRNA for structural and functional integrity. Eukaryotic cells use several different mechanisms, collectively known as mRNA surveillance, to look for irregularities in mRNAs. Irregular or aberrant mRNA are rapidly degraded by various enzymes. If a defective mRNA escapes the surveillance, it would be translated into a protein which would either be non-functional or not function properly. One of the primary irregularities in...

Nuclear Export of mRNA

Nuclear Export of mRNA

Before mRNAs are exported to the cytoplasm, it is crucial to check each mRNA for structural and functional integrity. Eukaryotic cells use several different mechanisms, collectively known as mRNA surveillance, to look for irregularities in mRNAs. Irregular or aberrant mRNA are rapidly degraded by various enzymes. If a defective mRNA escapes the surveillance, it would be translated into a protein which would either be non-functional or not function properly. One of the primary irregularities in...

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Related Experiment Video

Updated: Jul 13, 2026

Assay to Measure Nucleocytoplasmic Transport in Real Time within Motor Neuron-like NSC-34 Cells

Assay to Measure Nucleocytoplasmic Transport in Real Time within Motor Neuron-like NSC-34 Cells

Published on: May 16, 2017

Reversibility in nucleocytoplasmic transport.

Ronen Benjamine Kopito¹, Michael Elbaum

¹Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel.

Proceedings of the National Academy of Sciences of the United States of America

|July 25, 2007

Summary

Nuclear transport isn't a one-way street. Proteins can move bidirectionally between the nucleus and cytoplasm, challenging the idea of irreversible cargo delivery and suggesting open communication.

More Related Videos

Single-Molecule Imaging of Nuclear Transport

Single-Molecule Imaging of Nuclear Transport

Published on: June 9, 2010

Related Experiment Videos

Last Updated: Jul 13, 2026

Assay to Measure Nucleocytoplasmic Transport in Real Time within Motor Neuron-like NSC-34 Cells

Assay to Measure Nucleocytoplasmic Transport in Real Time within Motor Neuron-like NSC-34 Cells

Published on: May 16, 2017

Single-Molecule Imaging of Nuclear Transport

Single-Molecule Imaging of Nuclear Transport

Published on: June 9, 2010

Area of Science:

Cell Biology
Biophysics

Background:

Nucleocytoplasmic transport is crucial for cellular function, mediated by receptors and regulated by the GTPase Ran.
A common assumption is that nuclear import is irreversible.

Purpose of the Study:

To investigate the kinetics and reversibility of nuclear import and accumulation.
To challenge the perception of irreversible nuclear protein delivery.

Main Methods:

Quantitative measurements using cell-free nuclei in Xenopus egg extract.
Analysis of nuclear accumulation kinetics and steady-state levels.
Demonstration of reversibility via cytosolic medium exchange and fluorescence recovery after photobleaching.

Main Results:

Nuclear accumulation follows first-order kinetics and saturates according to Michaelis-Menten kinetics.
Evidence suggests receptor-mediated translocation across nuclear pores is bidirectional.
Demonstrated reversibility of nuclear accumulation through experimental manipulation.

Conclusions:

Nuclear import is a reversible process, not a one-way delivery.
Nuclear localization signals govern population fate, not individual molecule directionality.
This implies dynamic, bidirectional communication between the nucleus and cytoplasm.