Related Experiment Video
Updated: May 3, 2026
09:40
In Vivo Detection and Analysis of Rb Protein SUMOylation in Human Cells
Published on: November 2, 2017
6.6K
The nucleoporin RanBP2 has SUMO1 E3 ligase activity
Andrea Pichler1, Andreas Gast, Jacob S Seeler
1Max-Planck Institute for Biochemistry, Am Klopferspitz 18a, 82152 Martinsried, Germany.
Cell
|January 17, 2002
Summary
The nucleoporin RanBP2/Nup358 exhibits SUMO1 E3-like activity, enhancing SUMOylation by interacting with the Ubc9 enzyme. This finding links protein modification to nuclear import at the NPC.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Posttranslational modification via SUMOylation regulates key protein functions, including interactions, localization, and stability.
- SUMOylation pathways involve the E1 enzyme (Aos1/Uba2) and the E2 enzyme (Ubc9), with PIAS proteins identified as E3-like factors.
- The nuclear pore complex (NPC) is crucial for regulating transport between the nucleus and cytoplasm.
Purpose of the Study:
- To investigate the potential SUMO E3-like activity of the nucleoporin RanBP2/Nup358.
- To characterize the mechanism and specific domain responsible for RanBP2/Nup358's SUMO E3-like activity.
- To determine the functional implications of RanBP2/Nup358-mediated SUMOylation in relation to nuclear import.
Main Methods:
- Biochemical assays to assess SUMO1 transfer enhancement.
- Protein interaction studies to identify interactions between RanBP2/Nup358 and Ubc9.
- Mapping of the SUMO E3-like activity domain within RanBP2/Nup358.
- Localization studies of SUMOylation activity at the NPC.
Main Results:
- RanBP2/Nup358 demonstrates SUMO1 E3-like activity, independent of PIAS proteins and RING finger motifs.
- RanBP2/Nup358 directly interacts with the E2 enzyme Ubc9.
- The E3-like activity resides within a specific 33 kDa domain of RanBP2/Nup358.
- SUMOylation activity mediated by RanBP2/Nup358 is localized to the cytoplasmic filaments of the NPC.
Conclusions:
- RanBP2/Nup358 functions as a novel SUMO1 E3-like ligase.
- The study identifies a direct link between SUMOylation, mediated by a nucleoporin, and the nuclear import process.
- These findings suggest that protein modification and transport are coordinated events at the NPC.
Related Concept Videos
02:55The Nucleolus
8.6K
The nucleolus is the most prominent substructure of the nucleus. When it was first discovered, it was considered to be an isolated organelle that forms fibrils and granules. In 1931, the relationship between the nucleolus and chromosomes was first described by Heitz. He observed that the appearance and size of nucleolus varies depending on the stage of the cell cycle. He also noticed constricted regions on different chromosomes clustered together at definite cell cycle stages. These regions,...
8.6K
01:34Nuclear Protein Sorting
4.8K
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...
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...
4.8K
01:46Nuclear Localization Signals and Import
6.2K
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...
6.2K
01:42Nuclear Export
3.7K
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...
NES are of three types- the canonical 10-residue long leucine-rich signal and other...
3.7K
01:42Directionality of Nuclear Transport
3.9K
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...
3.9K
01:45Regulation of Nuclear Protein Sorting
2.5K
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...
2.5K