Related Experiment Video

Updated: Dec 17, 2025

In Vitro Analysis of E3 Ubiquitin Ligase Function
06:06

In Vitro Analysis of E3 Ubiquitin Ligase Function

Published on: May 14, 2021

5.9K

Isoleucine 44 Hydrophobic Patch Controls Toxicity of Unanchored, Linear Ubiquitin Chains through NF-κB Signaling

Jessica R Blount1, Kozeta Libohova1, Gustavo M Silva2

  • 1Department of Pharmacology, Wayne State University School of Medicine, 540 East Canfield St., Scott Hall Rm. 3108, Detroit, MI 48201, USA.

Cells
|June 26, 2020
PubMed

Insights

Free ubiquitin chains are generally not toxic in fruit flies. However, linear chains that cannot be modified can cause toxicity by upregulating NF-κB signaling.

Area of Science:

  • Cellular Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Ubiquitination is a crucial post-translational modification regulating cellular processes.
  • Accumulation of unanchored poly-ubiquitin chains is often considered toxic.
  • Previous studies indicated transgenic unanchored poly-ubiquitin is not problematic in *Drosophila melanogaster*.

Purpose of the Study:

  • To investigate the conditions under which free poly-ubiquitin chains become toxic.
  • To explore the relationship between unanchored chain topology and cellular toxicity.
  • To identify molecular mechanisms underlying unanchored poly-ubiquitin toxicity.

Main Methods:

  • Utilizing *Drosophila melanogaster* as a model organism.
  • Examining the effects of different poly-ubiquitin chain topologies.
  • Assessing the role of NF-κB signaling pathway components.
  • Investigating the impact of specific ubiquitin residues, such as isoleucine 44.

Main Results:

  • Unanchored poly-ubiquitin chains can be toxic when they are linear and cannot be modified.
  • These toxic linear chains lead to the upregulation of NF-κB signaling.
  • Modulating NF-κB component levels can mitigate the toxicity.
  • The toxicity of linear chains is regulated by isoleucine 44 on ubiquitin.

Conclusions:

  • Free ubiquitin chains are toxic only under specific, restricted cellular conditions.
  • The inability to modify linear ubiquitin chains contributes to toxicity.
  • NF-κB signaling is a key pathway involved in mediating this toxicity.
  • Cellular regulation of ubiquitin chain topology is critical for preventing toxicity.
Keywords:
Drosophila melanogasterNF-κB signalinginnate immunityubiquitinationunanchored poly-ubiquitin

More Related Videos

In Vitro Ubiquitination and Deubiquitination Assays of Nucleosomal Histones11:36

In Vitro Ubiquitination and Deubiquitination Assays of Nucleosomal Histones

Published on: July 25, 2019

11.2K
Ubiquitin Chain Analysis by Parallel Reaction Monitoring08:33

Ubiquitin Chain Analysis by Parallel Reaction Monitoring

Published on: June 17, 2020

3.9K

Related Concept Videos

Regulation of the Unfolded Protein Response01:31

Regulation of the Unfolded Protein Response

Inositol-requiring kinase one or IRE1 is the most conserved eukaryotic unfolded protein response (UPR) receptor. It is a type I transmembrane protein kinase receptor with a distinctive site-specific RNase activity. As the binding mechanics of the misfolded proteins with the N-terminal domain of IRE-1 are unclear, three binding models — direct, indirect, and allosteric -- are proposed for receptor activation. Nevertheless, it is known that once a misfolded protein associates with IRE1, it...
2.9K
NF-κB-dependent Signaling Pathway02:26

NF-κB-dependent Signaling Pathway

The transcription factor NF-κB was discovered in 1986 in the lab of Nobel laureate Professor David Baltimore, for its interaction with the immunoglobulin light chain enhancer in B-cells. After more than three decades of study, it is now evident that NF-κB regulates the expression of over 100 genes. Most of these genes play an essential role in the innate and adaptive immune responses as well as the inflammatory responses of animals.
NF-κB-dependent Signaling Mechanism
The...
9.7K
Covalently Linked Protein Regulators02:04

Covalently Linked Protein Regulators

Proteins can undergo many types of post-translational modifications, often in response to changes in their environment. These modifications play an important role in the function and stability of these proteins. Covalently linked molecules include functional groups, such as methyl, acetyl, and phosphate groups, and also small proteins, such as ubiquitin. There are around 200 different types of covalent regulators that have been identified.
These groups modify specific amino acids in a protein....
8.5K
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...
3.1K
Regulated Protein Degradation02:58

Regulated Protein Degradation

It is vital to regulate the activity of enzymatic as well as non-enzymatic proteins inside the cell. This can be achieved either through creating a balance between their rate of synthesis and degradation or regulating the intrinsic activity of the protein. Both these regulation mechanisms play an essential role in the normal functioning of cells.
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
8.5K
The Unfolded Protein Response01:37

The Unfolded Protein Response

The ER is the hub of protein synthesis in a cell. It has robust systems to quality control protein folding and also for degradation of terminally misfolded proteins. Under normal conditions, a small proportion of misfolded proteins that cannot be salvaged need to be transported to the cytoplasm by the ER-associated degradation or ERAD pathways. However, if the ERAD cannot handle the misfolded proteins, the cell activates the unfolded protein response or UPR to adjust the protein folding...
6.1K