The helicase CaHmi1p is required for wild-type mitochondrial DNA organization in Candida albicans

Area of Science:

• Molecular Biology
• Yeast Genetics
• Mitochondrial DNA Maintenance

Background:

• Mitochondrial DNA (mtDNA) maintenance mechanisms in petite-negative yeasts are not well understood.
• The DNA helicase Hmi1p is known to be important for mtDNA stability in Saccharomyces cerevisiae.

Purpose of the Study:

• To investigate the role of Hmi1p in mtDNA stability in the petite-negative yeast Candida albicans.
• To characterize the biochemical function and mitochondrial localization of Candida albicans Hmi1p (CaHmi1p).

Main Methods:

• Bioinformatic analysis for mitochondrial targeting signal identification.
• Biochemical assays to determine DNA helicase activity (ATP-dependent 3'-5' DNA unwinding).
• Gene deletion experiments to assess the impact of HMI1 on mtDNA integrity and mass.
• Mitochondrial nucleoid distribution analysis.

Main Results:

• CaHmi1p possesses a functional mitochondrial targeting signal and exhibits ATP-dependent DNA unwinding activity.
• Deletion of HMI1 in C. albicans leads to significant mtDNA fragmentation, reduced mtDNA mass, and altered nucleoid distribution, but not complete mtDNA loss.
• Specific mitochondrial genome regions are affected by CaHMI1 deletion, and fragmentation is reversible upon CaHmi1p reintroduction.

Conclusions:

• Hmi1p is crucial for maintaining mitochondrial genome stability in Candida albicans, a petite-negative yeast.
• This study demonstrates for the first time that a gene essential for mtDNA maintenance in S. cerevisiae is nonessential in a petite-negative yeast like C. albicans.
• The findings highlight differences in mtDNA maintenance strategies between yeast species.