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Related Experiment Videos

Mitochondrial DNA ligase function in Saccharomyces cerevisiae.

S L Donahue1, B E Corner, L Bordone

  • 1Department of Pharmacology, University of Minnesota Medical School, 6-120 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA.

Nucleic Acids Research
|March 27, 2001
PubMed
Summary

This study investigated the role of the CDC9 gene in mitochondrial DNA processes in yeast. Researchers found that the protein Cdc9p is the only DNA ligase present in yeast mitochondria. When Cdc9p was inactivated, mitochondrial DNA levels dropped rapidly. The study also tested whether another protein, Dnl4p, plays a role in mitochondrial DNA dynamics, but found no evidence of its involvement. To test DNA repair, an endonuclease was used to create DNA breaks in mitochondria. While wild-type and Dnl4p-deficient yeast recovered from this damage, Cdc9p-deficient clones did not. These findings suggest that Cdc9p is essential for maintaining mitochondrial DNA and for recovery from DNA damage in yeast.

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Area of Science:

  • Molecular genetics within yeast biology
  • Mitochondrial DNA repair mechanisms
  • Eukaryotic DNA ligase function

Background:

Prior research has shown that the CDC9 gene in Saccharomyces cerevisiae encodes a DNA ligase with nuclear roles in DNA replication and repair. However, the function of this protein in mitochondria remains unclear. No prior work had resolved whether other DNA ligases exist in yeast mitochondria. This gap motivated an investigation into the specific role of Cdc9p in mitochondrial DNA dynamics. Established knowledge includes the presence of Cdc9p in both nuclear and mitochondrial compartments. Yet, the extent of its mitochondrial activity was not fully understood. No prior studies had directly tested the necessity of Cdc9p for mitochondrial DNA maintenance. This uncertainty drove the current study to explore the role of Cdc9p in mitochondrial DNA processes.

Purpose Of The Study:

The aim of this study was to determine whether Cdc9p is the sole DNA ligase in yeast mitochondria and to assess its role in mitochondrial DNA dynamics. The specific problem addressed was the lack of clarity about mitochondrial DNA ligase function in S. cerevisiae. The motivation stemmed from the need to understand how mitochondrial DNA is maintained and repaired in the absence of other potential ligases. Researchers sought to clarify the role of Cdc9p in both replication and damage recovery processes. The study also aimed to test whether Dnl4p contributes to mitochondrial DNA function. The authors wanted to establish whether Cdc9p is essential for mitochondrial DNA stability. This investigation focused on the biochemical and functional roles of Cdc9p in mitochondria.

Keywords:
mitochondrial DNA repairyeast DNA ligaseSaccharomyces cerevisiaeDNA replication in mitochondria

Frequently Asked Questions

The authors propose that Cdc9p is the sole DNA ligase in yeast mitochondria and is essential for DNA replication and repair.

The Escherichia coli ECO:RI endonuclease was targeted to mitochondria to create double-strand breaks.

The Deltadnl4 strain was used to determine whether Dnl4p contributes to mitochondrial DNA dynamics.

The endonuclease was used to induce DNA damage and test recovery mechanisms in mitochondrial DNA.

Cdc9p inactivation led to a rapid decline in mitochondrial DNA content in both dividing and stationary yeast cultures.

Related Experiment Videos

Main Methods:

The study used biochemical analysis of mitochondrial protein extracts to identify DNA ligase activity. Researchers analyzed protein extracts from yeast mitochondria to determine the presence of DNA ligase. The CDC9 gene product was tested for its activity in mitochondrial DNA processes. The Deltadnl4 strain was used to assess the role of Dnl4p in mitochondrial DNA dynamics. An Escherichia coli ECO:RI endonuclease was targeted to mitochondria to induce DNA damage. Transient expression of the recombinant endonuclease was used to create double-strand breaks. The ability of yeast strains to recover from this damage was observed. Wild-type and Deltadnl4 strains were compared to Cdc9p-deficient clones for recovery capacity.

Main Results:

Biochemical analysis confirmed that Cdc9p is the sole DNA ligase in yeast mitochondria. Inactivation of mitochondrial Cdc9p led to a rapid decline in mitochondrial DNA content. This decline occurred in both dividing and stationary yeast cultures. No apparent defect in mitochondrial DNA dynamics was observed in Deltadnl4 strains. Transient expression of ECO:RI endonuclease induced mitochondrial DNA double-strand breaks. Wild-type and Deltadnl4 yeast rapidly recovered from this damage. In contrast, Cdc9p-deficient clones failed to recover from mitochondrial DNA damage. These findings suggest that Cdc9p is essential for mitochondrial DNA replication and repair.

Conclusions:

The authors propose that Cdc9p is the sole DNA ligase required for mitochondrial DNA processes in S. cerevisiae. The study supports the conclusion that Cdc9p is essential for mitochondrial DNA replication. The results suggest that Cdc9p is also necessary for recovery from mitochondrial DNA damage. No other DNA ligase appears to compensate for the loss of Cdc9p in mitochondria. The findings indicate that Dnl4p is not involved in mitochondrial DNA dynamics. The authors conclude that Cdc9p is critical for maintaining mitochondrial DNA content. The study highlights the importance of Cdc9p in both spontaneous and induced DNA damage recovery. These conclusions are based on the observed effects of Cdc9p inactivation and endonuclease-induced damage.

The results suggest that Cdc9p is the only DNA ligase required for mitochondrial DNA replication and damage recovery.