Related Experiment Video
Updated: Jan 15, 2026
Gene-targeted Random Mutagenesis to Select Heterochromatin-destabilizing Proteasome Mutants in Fission Yeast
Published on: May 15, 2018
Proteasome regulation of petite-negativity in fission yeast
Katie Lin Amberg1, Lyrica Hao1, Susanne Cranz-Mileva1
1Department of Molecular Biology and Biochemistry, Division of Life Sciences, Rutgers, the State University of New Jersey, Piscataway, USA.
Background:
Mitochondria carry out essential functions in eukaryotic cells. The mitochondrial genome encodes factors critical to support oxidative phosphorylation and mitochondrial protein import necessary for these functions. However, organisms like budding yeast can readily lose their mitochondrial genome, yielding respiration-deficient petite mutants. The fission yeast Schizosaccharomyces pombe is petite-negative, but some nuclear mutations enable the loss of its mitochondrial genome.
Results:
Here, we characterize the classical petite-positive mutation ptp1-1 as a loss of function allele of the proteasome 19S regulatory subunit component mts4/rpn1, involved in the ubiquitin-dependent degradation pathway. By comparison with another petite-enabling mutation in the g-subunit of the F1-ATPase, we show that ptp1-1 does not rescue mitochondrial membrane potential. Instead, the mutation results in increased levels of mitochondrial and cytoplasmic chaperones and an altered oxidative stress response.
Conclusions:
ptp1-1 is a partial loss of function mutation of the proteasome that enables growth of cells devoid of mitochondrial DNA through a mechanism that is independent of mitochondrial membrane potential rescue and associated with proteasome-dependent regulation of mitochondrial protein import precursors and the oxidative stress response.
Insights
The proteasome mutation ptp1-1 allows fission yeast to lose mitochondrial DNA. This occurs independently of mitochondrial membrane potential, affecting protein import and stress responses.
Area of Science:
- Cell Biology
- Genetics
- Molecular Biology
Background:
- Mitochondria are vital for eukaryotic cells, with their genome encoding essential proteins.
- While budding yeast readily lose mitochondrial DNA, fission yeast (Schizosaccharomyces pombe) are petite-negative, requiring specific mutations for mitochondrial DNA loss.
Purpose of the Study:
- To characterize the petite-positive mutation ptp1-1 in fission yeast.
- To elucidate the mechanism by which ptp1-1 enables mitochondrial genome loss.
Main Methods:
- Characterization of the ptp1-1 mutation as a loss-of-function allele of mts4/rpn1, a proteasome subunit.
- Comparative analysis with a mutation in the F1-ATPase g-subunit.
- Assessment of mitochondrial membrane potential, chaperone levels, and oxidative stress response.
Main Results:
- ptp1-1 is a partial loss-of-function mutation in the proteasome component mts4/rpn1.
- The mutation does not restore mitochondrial membrane potential in petite cells.
- Increased mitochondrial and cytoplasmic chaperones and an altered oxidative stress response were observed.
Conclusions:
- The ptp1-1 mutation enables growth without mitochondrial DNA through a proteasome-dependent mechanism.
- This mechanism is independent of rescuing mitochondrial membrane potential.
- It involves regulation of mitochondrial protein import precursors and the oxidative stress response.
More Related Videos
Related Concept Videos
01:13The Proteasome
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. This involves participation of a series of enzymes including— E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...
02:18The Proteasome
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. A series of enzymes carry out the ubiquitination of the target proteins - E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...
02:18The Proteasome
01:45Regulation of Nuclear Protein Sorting
01:17The Proteasome Structure
The proteasome is an...
02:58Regulated Protein Degradation
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...