Nicolas Jauniaux | PubMed Health

PubMed2004

Genome evolution in yeasts.

Identifying the mechanisms of eukaryotic genome evolution by comparative genomics is often complicated by the multiplicity of events that have taken place throughout the history of individual lineages, leaving only distorted and superimposed traces in the genome of each living organism. The hemiascomycete yeasts, with their compact genomes, similar lifestyle and distinct sexual and physiological properties, provide a unique opportunity to explore such mechanisms. We present here the complete, assembled genome sequences of four yeast species, selected to represent a broad evolutionary range within a single eukaryotic phylum, that after analysis proved to be molecularly as diverse as the entire phylum of chordates. A total of approximately 24,200 novel genes were identified, the translation products of which were classified together with Saccharomyces cerevisiae proteins into about 4,700 families, forming the basis for interspecific comparisons. Analysis of chromosome maps and genome redundancies reveal that the different yeast lineages have evolved through a marked interplay between several distinct molecular mechanisms, including tandem gene repeat formation, segmental duplication, a massive genome duplication and extensive gene loss.

Chromosomes, Fungal↗

PubMed2004

High levels of the mitochondrial large ribosomal subunit protein 40 prevent loss of mitochondrial DNA in null mmf1 Saccharomyces cerevisiae cells.

Members of the YERO57c/YJGFc/UK114 protein family have been identified in bacteria and eukaryotes. The budding yeast Saccharomyces cerevisiae contains two different proteins of this family, Hmf1p and Mmf1p. We have previously shown that Mmf1p is a mitochondrial protein functionally related to its human homologue and able to influence the maintenance of mitochondrial DNA. Deletion of Mmf1 results in loss of the mitochondrial genome. Using a multicopy suppression approach, we have identified a protein of the mitochondrial large ribosomal subunit, MRPL40, which stabilizes mtDNA in Deltammf1 cells. Overexpression of MRPL40 did not prevent loss of mtDNA in a mutant strain lacking the mitochondrial protein Abf2p. Thus, MRPL40 does not have a general effect on mtDNA stability, but it may be specific for the mmf1-null strain. We also show that the Deltamrpl40 cells present a similar phenotype to the mmf1-null strain, having reduced mtDNA stability and growth rate. Furthermore, we observed that rho(+)Deltamrpl40 haploid cells can be obtained when tetrads are directly dissected on medium containing a non-fermentable carbon source. Thus, replication and segregation of the mtDNA can occur in the absence of MRPL40. We also show that another mitochondrial ribosomal protein, MRPL38, is able to overcome the Deltammf1-associated defect. Together, our results suggest a link between Mmf1p and the two mitochondrial ribosomal proteins.

Blotting, Western↗