Project description:To explore the aberrant expression patterns between hybrid sexes, we compare the global gene expression of 7-day-old whole body adults of hybrids by sex in recently diverged Drosophia pseudoobscura group
Project description:To explore the aberrant expression patterns between hybrid sexes, we compare the global gene expression of 7-day-old whole body adults of hybrids by sex in recently diverged Drosophia pseudoobscura group 7-day-old virgin hybrid flies were assayed by sex. Reciprocal F1 hybrids were produced for D. pseudoobscura/D. persimilis and D. pseudoobscura/D. p. bogotana crosses by mass mating virgin flies. At least three isofemale inbred lines were used for each species (D. pseudoobscura; D. persimilis; D. pseudoobscura bogotana).Two separate labeling reactions per sample were pooled and hybridized to the Agilent single color (Cyanine 3-CTP dye) arrays. Three different replicates were hybridized for each hybrid and sex. Pure species data (collected the same time and deposited as GSE17192 ) and hybrid data were analyzed together to determine the misexpression differences between hybrid males and females.
Project description:Hybrid progeny can enjoy increased fitness and stress tolerance relative to their ancestral species, a phenomenon known as hybrid vigor. Though this phenomenon has been documented throughout the Eukarya, evolution of hybrid populations has yet to be explored experimentally in the lab. To fill this knowledge gap we created a pool of Saccharomyces cerevisiae and S. bayanus homoploid and aneuploid hybrids, and then investigated how selection in the form of incrementally increased temperature or ethanol impacted hybrid genome structure and adaptation. During 500 generations of continuous ammonia-limited, glucose-sufficient culture, temperature was raised from 25C to 46??C. This selection invariably resulted in nearly-complete loss of the S. bayanus genome, although the dynamics of genome loss differed among independent replicates. Temperature-evolved isolates were significantly more thermal tolerant and exhibited greater phenotypic plasticity than parental species and founding hybrids. By contrast, when the same hybrid pool was subjected to increases in exogenous ethanol from 0% to 14%, selection favored euploid S. cerevisiae x S. bayanus hybrids. Ethanol-evolved isolates exhibited significantly greater ethanol tolerance relative only to S. bayanus and one of the founding hybrids tested. Adaptation to thermal and ethanol stress manifested as heritable changes in cell wall structure demonstrated by resistance to zymolyase or micafungin treatment. This is the first study to show experimentally that the fate of interspecific hybrids critically depends on the type of selection they encounter during the course of evolution.
Project description:Super killer (SKI) complex is a well-known cytoplasmic 3′ to 5′ mRNA decay complex that functions with the exosome to degrade excessive and aberrant mRNAs. Recently, SKIV2L, the 3′ to 5′ RNA helicase of the human SKI (hSKI) complex has been implicated with the extraction of mRNA at stalled ribosomes, tackling aberrant translation. Here, we show that SKIV2L and TTC37 of the hSKI complex are present within the nucleus, localise on chromatin and at some telomeres during the G2 cell cycle phase. In cells, SKIV2L prevents telomere replication stress shown as fragile telomeres and increases the stability of telomere DNA-RNA hybrids in G2 of the cell cycle whereas its absence decreases the amount of those structures. We further demonstrate that purified hSKI complex binds telomeric DNA and RNA substrates in vitro. Moreover, SKIV2L association with telomeres is dependent on DNA-RNA hybrids but its helicase activity is dispensable for its telomeric function. Taken together, our results provide a nuclear function for SKIV2L of the hSKI complex in overcoming replication stress at telomeres mediated by its recruitment to DNA-RNA hybrid structures in G2 and thus maintaining telomere stability.
Project description:Hybrid progeny can enjoy increased fitness and stress tolerance relative to their ancestral species, a phenomenon known as hybrid vigor. Though this phenomenon has been documented throughout the Eukarya, evolution of hybrid populations has yet to be explored experimentally in the lab. To fill this knowledge gap we created a pool of Saccharomyces cerevisiae and S. bayanus homoploid and aneuploid hybrids, and then investigated how selection in the form of incrementally increased temperature or ethanol impacted hybrid genome structure and adaptation. During 500 generations of continuous ammonia-limited, glucose-sufficient culture, temperature was raised from 25C to 46??C. This selection invariably resulted in nearly-complete loss of the S. bayanus genome, although the dynamics of genome loss differed among independent replicates. Temperature-evolved isolates were significantly more thermal tolerant and exhibited greater phenotypic plasticity than parental species and founding hybrids. By contrast, when the same hybrid pool was subjected to increases in exogenous ethanol from 0% to 14%, selection favored euploid S. cerevisiae x S. bayanus hybrids. Ethanol-evolved isolates exhibited significantly greater ethanol tolerance relative only to S. bayanus and one of the founding hybrids tested. Adaptation to thermal and ethanol stress manifested as heritable changes in cell wall structure demonstrated by resistance to zymolyase or micafungin treatment. This is the first study to show experimentally that the fate of interspecific hybrids critically depends on the type of selection they encounter during the course of evolution. Array-CGH was performed on the S. cerevisiae parent strain CEN.PK (GSY2160), the S. bayanus parent strain CBS7001 (GSY2161) and on the F1 interspecific hybrid resulting from mating the 2 parents (GSY2168). Additionally, three rare viable spores obtained after sporulation of the F1 were assayed by array-CGH (F2a, F2b, F2c). A large pool of F2 spores (and probably some number of F1 hybrid cells) were subjected to gradually increasing temperatures, in three independent vessels, with populations sampled at various generation times. Likewise, the same pool was used to found populations in an additional three independent vessels, which were then subjected to gradually increasing ethanol concentrations (at constant temperature). Array-CGH was performed on three different clones from each of the three temperature vessels at the final 500 generation time point (T500 clones). Biological replicates of the T500 clones were performed (T500-new). Two self-self array-CGH hybridization controls were also performed (self-control). Array-CGH was performed on one clone from each of the three ethanol vessels taken at the 400 generation timepoint (EtOH400gen clones).
Project description:At critically short telomeres TERRA RNA-DNA hybrids become stabilized and drive homology-directed repair (HDR) to delay replicative senescence. However, even at long- and intermediate-length telomeres, not subject to HDR, transient TERRA RNA-DNA hybrids form, suggestive of additional roles. Here, we report that hybrids at telomeres prevent resection by the Exo1 nuclease when telomeres become non-functional. We employed the well-characterized cdc13-1 allele, where telomere resection can be induced in a temperature dependent manner, to demonstrate that ssDNA generation at telomeres is either prevented or augmented when RNA-DNA hybrids are stabilized or destabilized, respectively. The viability of cdc13-1 cells is affected by the presence or absence of hybrids accordingly. These results give insights into an additional role of TERRA at dysfunctional telomeres suggesting that it not only affects replicative senescence rates through HDR activation at critically short telomeres, but may also affect resection rates at intermediate length telomeres in pre-senescent cells.
Project description:Mapping of RNA:DNA hybrids in human cells reveals a number of characteristics of these non-canonical nucleic acid structures. A directional sequencing approach reveals the RNA component of the RNA:DNA hybrid to be purine-rich, indicating a thermodynamic contribution to the stability of these structures. The RNA:DNA hybrids are enriched at loci with decreased DNA methylation and increased DNase hypersensitivity, and within larger domains with characteristics of heterochromatin formation. Studies of chromatin at RNA:DNA hybrids shows the presence of the ILF2 and ILF3 transcription factors, supporting a model of certain transcription factors binding preferentially to the RNA:DNA conformation. Overall, there is little to indicate a dependence for RNA:DNA hybrids forming co-transcriptionally, with results from the ribosomal DNA repeat unit instead supporting a model of RNA generating these structures in trans. The results of the study indicate heterogeneous functions of these genomic elements and new insights into their formation and stability in vivo. Investigation of locatization of RNA in RNA:DNA hybrids genome-wide in HEK293T and IMR-90 cells through RNA:DNA hybrid immunorprecipitation strand-specific sequencing
Project description:Mapping of RNA:DNA hybrids in human cells reveals a number of characteristics of these non-canonical nucleic acid structures. A directional sequencing approach reveals the RNA component of the RNA:DNA hybrid to be purine-rich, indicating a thermodynamic contribution to the stability of these structures. The RNA:DNA hybrids are enriched at loci with decreased DNA methylation and increased DNase hypersensitivity, and within larger domains with characteristics of heterochromatin formation. Studies of chromatin at RNA:DNA hybrids shows the presence of the ILF2 and ILF3 transcription factors, supporting a model of certain transcription factors binding preferentially to the RNA:DNA conformation. Overall, there is little to indicate a dependence for RNA:DNA hybrids forming co-transcriptionally, with results from the ribosomal DNA repeat unit instead supporting a model of RNA generating these structures in trans. The results of the study indicate heterogeneous functions of these genomic elements and new insights into their formation and stability in vivo. Investigation of expression data genome-wide in HEK293T and IMR-90 cells through RNA-seq, including rRNA
Project description:Mapping of RNA:DNA hybrids in human cells reveals a number of characteristics of these non-canonical nucleic acid structures. A directional sequencing approach reveals the RNA component of the RNA:DNA hybrid to be purine-rich, indicating a thermodynamic contribution to the stability of these structures. The RNA:DNA hybrids are enriched at loci with decreased DNA methylation and increased DNase hypersensitivity, and within larger domains with characteristics of heterochromatin formation. Studies of chromatin at RNA:DNA hybrids shows the presence of the ILF2 and ILF3 transcription factors, supporting a model of certain transcription factors binding preferentially to the RNA:DNA conformation. Overall, there is little to indicate a dependence for RNA:DNA hybrids forming co-transcriptionally, with results from the ribosomal DNA repeat unit instead supporting a model of RNA generating these structures in trans. The results of the study indicate heterogeneous functions of these genomic elements and new insights into their formation and stability in vivo.