Heterochromatin epimutations impose mitochondrial dysfunction to confer antifungal resistance

Area of Science:

• Epigenetics and Gene Regulation
• Mitochondrial Biology
• Antifungal Resistance Mechanisms

Background:

• Antifungal resistance poses a significant threat to global health and food security.
• Fission yeast, Schizosaccharomyces pombe, exhibits reversible epimutations conferring resistance to various stressors.
• Resistant epimutants display heterochromatin islands at specific gene loci, leading to gene repression.

Purpose of the Study:

• To investigate the role of mitochondrial protein repression via heterochromatin islands in conferring antifungal resistance.
• To elucidate the molecular mechanisms linking mitochondrial dysfunction to drug resistance in fission yeast.
• To explore the potential conservation of this resistance mechanism in pathogenic fungi.

Main Methods:

• Analysis of fission yeast epimutants with ectopic histone-H3K9 methylation.
• Genetic manipulation (cup1-tt, ppr4Δ) to mimic epimutational effects.
• Assessment of mitochondrial function (respiration, growth, reactive oxygen species).
• Transcriptomic analysis to identify activated pathways (e.g., Pap1 transcription factor).

Main Results:

• Repression of mitochondrial genes Cup1 and Ppr4 by heterochromatin islands confers resistance.
• Genetic mutants (cup1-tt, ppr4Δ) exhibit mitochondrial dysfunction and phenocopy epimutants.
• Mitochondrial dysfunction activates the Pap1 oxidative stress response and mitonuclear retrograde pathways, increasing efflux activity.

Conclusions:

• Fission yeast utilizes epimutations inducing mitochondrial dysfunction as a strategy to overcome environmental insults and drug exposure.
• The observed mechanism, involving heterochromatin-mediated gene silencing and subsequent mitochondrial impairment, directly links to drug resistance.
• This epimutation-driven mitochondrial dysfunction pathway is likely a conserved mechanism contributing to antifungal resistance in pathogenic fungi.