Analysis of Gross Chromosomal Rearrangements in Budding Yeast
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ABSTRACT: Determine changes in genomic copy across the entire genome for isolated strains with selected gross chromosomal rearrangements relative to the wild-type strain.
Project description:Determine changes in genomic copy across the entire genome for isolated strains with selected gross chromosomal rearrangements relative to the wild-type strain.
Project description:Determine changes in genomic copy across the entire genome for isolated strains with selected gross chromosomal rearrangements relative to the wild-type strain
Project description:We investigated the effects of the ploidy on cellular response in strains carrying various types of gross chromosomal rearrangements.
Project description:We investigated the effects of the ploidy on cellular response in strains carrying various types of gross chromosomal rearrangements. Fourteen mutated strains (6 haploid strains and 8 diploid strains) were compared to their associated parental strain (haploid or diploid parental strain). For each comparison, 2 microarray experiments implying biological replicates were performed.
Project description:At the organismal level, genome rearrangements are usually deleterious and are often associated with disease. Yet, on an evolutionary scale, they can be beneficial as they provide for rapid genetic diversification. DNA lesions, particularly double-strand breaks (DSBs), are sources of genome instability that can be rectified by various repair processes. Homologous recombination (HR) is highly effective at protecting the genome from DSBs and provides for accurate repair between sister chromatids and homologous chromosomes. Here we show that although random DSBs induced by ionizing radiation in yeast chromosomes are repaired efficiently by HR in G-2 diploid cells, rearrangements are frequent. The chromosome aberrations (ABs) primarily resulted from recombination between Ty retrotransposable elements, the most abundant class of dispersed repetitive DNAs in the genome, while some rearrangements involved other classes of repetitive DNA. Few, if any, of the ABs could be attributed to nonhomologous end-joining (NHEJ). We conclude that only those few DSBs that fall at or near the 3-5% of the genome composed of repetitive DNA elements are effective at generating rearrangements, while other lesions that appear in unique (single copy) sequences are correctly repaired. Thus, by successfully competing with repair that normally occurs between large homologous chromosomal DNAs, the combination of repetitive elements and DSBs provides genome plasticity and a rich source of evolutionary opportunities. Keywords: CGH-array
Project description:At the organismal level, genome rearrangements are usually deleterious and are often associated with disease. Yet, on an evolutionary scale, they can be beneficial as they provide for rapid genetic diversification. DNA lesions, particularly double-strand breaks (DSBs), are sources of genome instability that can be rectified by various repair processes. Homologous recombination (HR) is highly effective at protecting the genome from DSBs and provides for accurate repair between sister chromatids and homologous chromosomes. Here we show that although random DSBs induced by ionizing radiation in yeast chromosomes are repaired efficiently by HR in G-2 diploid cells, rearrangements are frequent. The chromosome aberrations (ABs) primarily resulted from recombination between Ty retrotransposable elements, the most abundant class of dispersed repetitive DNAs in the genome, while some rearrangements involved other classes of repetitive DNA. Few, if any, of the ABs could be attributed to nonhomologous end-joining (NHEJ). We conclude that only those few DSBs that fall at or near the 3-5% of the genome composed of repetitive DNA elements are effective at generating rearrangements, while other lesions that appear in unique (single copy) sequences are correctly repaired. Thus, by successfully competing with repair that normally occurs between large homologous chromosomal DNAs, the combination of repetitive elements and DSBs provides genome plasticity and a rich source of evolutionary opportunities. Keywords: Band-array Each array in this series corresponds to the DNA of a yeast chromosomal band excised from a pulse-field gel (CHEF). Chromosomal aberrations identified in radiation survivors were analyzed by microarray to reveal which regions of the genome were present in the new chromosomes. The DNA enriched in the specific band appears in the arrays as continuos segments of spots with highly positive Log2 Red/Green ratios.
Project description:At the organismal level, genome rearrangements are usually deleterious and are often associated with disease. Yet, on an evolutionary scale, they can be beneficial as they provide for rapid genetic diversification. DNA lesions, particularly double-strand breaks (DSBs), are sources of genome instability that can be rectified by various repair processes. Homologous recombination (HR) is highly effective at protecting the genome from DSBs and provides for accurate repair between sister chromatids and homologous chromosomes. Here we show that although random DSBs induced by ionizing radiation in yeast chromosomes are repaired efficiently by HR in G-2 diploid cells, rearrangements are frequent. The chromosome aberrations (ABs) primarily resulted from recombination between Ty retrotransposable elements, the most abundant class of dispersed repetitive DNAs in the genome, while some rearrangements involved other classes of repetitive DNA. Few, if any, of the ABs could be attributed to nonhomologous end-joining (NHEJ). We conclude that only those few DSBs that fall at or near the 3-5% of the genome composed of repetitive DNA elements are effective at generating rearrangements, while other lesions that appear in unique (single copy) sequences are correctly repaired. Thus, by successfully competing with repair that normally occurs between large homologous chromosomal DNAs, the combination of repetitive elements and DSBs provides genome plasticity and a rich source of evolutionary opportunities. Keywords: Band-array
Project description:Genome rearrangements, especially amplifications and deletions, have regularly been observed as responses to sustained application of the same strong selective pressure in microbial populations growing in continuous culture. We studied eight strains of budding yeast (Saccharomyces cerevisiae) isolated after 100–500 generations of growth in glucose-limited chemostats. Changes in DNA copy number were assessed at single-gene resolution by using DNA microarray-based comparative genomic hybridization. Six of these evolved strains were aneuploid as the result of gross chromosomal rearrangements. Most of the aneuploid regions were the result of translocations, including three instances of a shared breakpoint on chromosome 14 immediately adjacent to CIT1, which encodes the citrate synthase that performs a key regulated step in the tricarboxylic acid cycle. Three strains had amplifications in a region of chromosome 4 that includes the high-affinity hexose transporters; one of these also had the aforementioned chromosome 14 break. Three strains had extensive overlapping deletions of the right arm of chromosome 15. Further analysis showed that each of these genome rearrangements was bounded by transposon-related sequences at the breakpoints. The observation of repeated, independent, but nevertheless very similar, chromosomal rearrangements in response to persistent selection of growing cells parallels the genome rearrangements that characteristically accompany tumor progression. Set of arrays organized by shared biological context, such as organism, tumors types, processes, etc. Computed
Project description:At the organismal level, genome rearrangements are usually deleterious and are often associated with disease. Yet, on an evolutionary scale, they can be beneficial as they provide for rapid genetic diversification. DNA lesions, particularly double-strand breaks (DSBs), are sources of genome instability that can be rectified by various repair processes. Homologous recombination (HR) is highly effective at protecting the genome from DSBs and provides for accurate repair between sister chromatids and homologous chromosomes. Here we show that although random DSBs induced by ionizing radiation in yeast chromosomes are repaired efficiently by HR in G-2 diploid cells, rearrangements are frequent. The chromosome aberrations (ABs) primarily resulted from recombination between Ty retrotransposable elements, the most abundant class of dispersed repetitive DNAs in the genome, while some rearrangements involved other classes of repetitive DNA. Few, if any, of the ABs could be attributed to nonhomologous end-joining (NHEJ). We conclude that only those few DSBs that fall at or near the 3-5% of the genome composed of repetitive DNA elements are effective at generating rearrangements, while other lesions that appear in unique (single copy) sequences are correctly repaired. Thus, by successfully competing with repair that normally occurs between large homologous chromosomal DNAs, the combination of repetitive elements and DSBs provides genome plasticity and a rich source of evolutionary opportunities. Keywords: CGH-array Diploid G-2 yeast cells were exposed to 80 krad of ionizing radiation and plated on rich media to obtain survivor colonies. Genomic DNA from each of 37 survivors (Cy5/red; JW1 to JW13, and A1 to A24) was competitively hybridized to DNA from the parent diploid strain (Cy3/green). Gains of genomic segments in the survivors were detected as continuous regions of positive Log2 Red:Green ratios, while losses were detected as negative Log2 Red:Green ratios.
Project description:Genome rearrangements, especially amplifications and deletions, have regularly been observed as responses to sustained application of the same strong selective pressure in microbial populations growing in continuous culture. We studied eight strains of budding yeast (Saccharomyces cerevisiae) isolated after 100–500 generations of growth in glucose-limited chemostats. Changes in DNA copy number were assessed at single-gene resolution by using DNA microarray-based comparative genomic hybridization. Six of these evolved strains were aneuploid as the result of gross chromosomal rearrangements. Most of the aneuploid regions were the result of translocations, including three instances of a shared breakpoint on chromosome 14 immediately adjacent to CIT1, which encodes the citrate synthase that performs a key regulated step in the tricarboxylic acid cycle. Three strains had amplifications in a region of chromosome 4 that includes the high-affinity hexose transporters; one of these also had the aforementioned chromosome 14 break. Three strains had extensive overlapping deletions of the right arm of chromosome 15. Further analysis showed that each of these genome rearrangements was bounded by transposon-related sequences at the breakpoints. The observation of repeated, independent, but nevertheless very similar, chromosomal rearrangements in response to persistent selection of growing cells parallels the genome rearrangements that characteristically accompany tumor progression. Set of arrays organized by shared biological context, such as organism, tumors types, processes, etc. Keywords: Logical Set