Isabelle Lesur | 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

The transcriptome of prematurely aging yeast cells is similar to that of telomerase-deficient cells.

To help define the pathologies associated with yeast cells as they age, we analyzed the transcriptome of young and old cells isolated by elutriation, which allows isolation of biochemical quantities of old cells much further advanced in their life span than old cells prepared by the biotin-streptavidin method. Both 18-generation-old wild-type yeast and 8-generation-old cells from a prematurely aging mutant (dna2-1), with a defect in DNA replication, were evaluated. Genes involved in gluconeogenesis, the glyoxylate cycle, lipid metabolism, and glycogen production are induced in old cells, signifying a shift toward energy storage. We observed a much more extensive generalized stress response known as the environmental stress response (ESR), than observed previously in biotin-streptavidin-isolated cells, perhaps because the elutriated cells were further advanced in their life span. In addition, there was induction of DNA repair genes that fall in the so-called DNA damage "signature" set. In the dna2-1 mutant, energy production genes were also induced. The response in the dna2-1 strain is similar to the telomerase delete response, genes whose expression changes during cellular senescence in telomerase-deficient cells. We propose that these results suggest, albeit indirectly, that old cells are responding to genome instability.

Cell Cycle↗