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Related Concept Videos

Nuclear Export of mRNA02:31

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 Protein Sorting01:34

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...
Nuclear Localization Signals and Import01:46

Nuclear Localization Signals and Import

Proteins targeted to the nucleus carry short stretches of amino acid sequences called the nuclear localization signal or NLS. Classical nuclear localization signals are of two types: monopartite and bipartite NLS. Monopartite classical NLS (cNLS) consists of a single cluster of 4-8 amino acids. Bipartite cNLS consists of two clusters of  2-3 amino acids and a 9-12 residue long proline-rich linker bridging the two clusters. Signal clusters are rich in positively charged amino acids such as...
Nuclear Export01:42

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...
Regulation of Nuclear Protein Sorting01:45

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...
Directing Proteins to the Rough Endoplasmic Reticulum01:34

Directing Proteins to the Rough Endoplasmic Reticulum

The organelle-specific signaling sequences direct proteins synthesized in the cytosol to their final destination like ER, mitochondria, peroxisomes, etc. Some of the proteins directed to ER are then trafficked via vesicles to other organelles within the cell or the extracellular environment through the Golgi complex. For example, the rough ER synthesizes soluble proteins for transportation to the lysosomes or secretion out of the cell. It can also synthesize transmembrane proteins that can...

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Related Experiment Video

Updated: May 7, 2026

A Protein Preparation Method for the High-throughput Identification of Proteins Interacting with a Nuclear Cofactor Using LC-MS/MS Analysis
05:43

A Protein Preparation Method for the High-throughput Identification of Proteins Interacting with a Nuclear Cofactor Using LC-MS/MS Analysis

Published on: January 24, 2017

San1p, checking up on nuclear proteins.

Thomas Sommer1, Christian Hirsch

  • 1Max-Delbrück Center for Molecular Medicine, Berlin, Germany.

Cell
|March 31, 2005
PubMed
Summary
This summary is machine-generated.

Scientists discovered a new nuclear protein quality control system. This system, involving the E3 ligase San1p, identifies and eliminates faulty nuclear proteins, ensuring cellular proteome accuracy.

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Visualization of Protein-protein Interaction in Nuclear and Cytoplasmic Fractions by Co-immunoprecipitation and In Situ Proximity Ligation Assay
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Visualization of Protein-protein Interaction in Nuclear and Cytoplasmic Fractions by Co-immunoprecipitation and In Situ Proximity Ligation Assay

Published on: January 16, 2017

Monitoring Protein-RNA Interaction Dynamics In Vivo at High Temporal Resolution Using χCRAC
09:15

Monitoring Protein-RNA Interaction Dynamics In Vivo at High Temporal Resolution Using χCRAC

Published on: May 9, 2020

Related Experiment Videos

Last Updated: May 7, 2026

A Protein Preparation Method for the High-throughput Identification of Proteins Interacting with a Nuclear Cofactor Using LC-MS/MS Analysis
05:43

A Protein Preparation Method for the High-throughput Identification of Proteins Interacting with a Nuclear Cofactor Using LC-MS/MS Analysis

Published on: January 24, 2017

Visualization of Protein-protein Interaction in Nuclear and Cytoplasmic Fractions by Co-immunoprecipitation and In Situ Proximity Ligation Assay
10:05

Visualization of Protein-protein Interaction in Nuclear and Cytoplasmic Fractions by Co-immunoprecipitation and In Situ Proximity Ligation Assay

Published on: January 16, 2017

Monitoring Protein-RNA Interaction Dynamics In Vivo at High Temporal Resolution Using χCRAC
09:15

Monitoring Protein-RNA Interaction Dynamics In Vivo at High Temporal Resolution Using χCRAC

Published on: May 9, 2020

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Cellular quality control is essential for maintaining proteome integrity.
  • Existing mechanisms primarily focus on cytoplasmic and endoplasmic reticulum protein surveillance.

Purpose of the Study:

  • To identify and characterize novel protein quality control systems within the cell nucleus.
  • To elucidate the components and function of a newly discovered nuclear surveillance pathway.

Main Methods:

  • Utilized yeast genetics and protein biochemistry techniques.
  • Investigated the role of the E3 ligase San1p in nuclear protein turnover.

Main Results:

  • Discovered a novel nuclear protein quality control system.
  • Identified San1p as a key E3 ligase responsible for targeting aberrant nuclear proteins for degradation.
  • Demonstrated that this system ensures the fidelity of the nuclear proteome.

Conclusions:

  • The nucleus possesses a dedicated protein quality control system.
  • San1p plays a crucial role in recognizing and eliminating misfolded or damaged nuclear proteins.
  • This pathway contributes significantly to maintaining genomic information accuracy at the proteome level.