Project description:Transcriptional networks have been shown to evolve very rapidly, prompting questions as to how such changes arise and are tolerated. Recent comparisons of transcriptional networks across species have implicated variations in the cis-acting DNA sequences near genes as the main cause of divergence. What is less clear is how these changes interact with trans-acting changes occurring elsewhere in the genetic circuit. Here, we report the discovery of a system of compensatory trans and cis mutations in the yeast AP-1 transcriptional network that allows for conserved transcriptional regulation despite continued genetic change. We pinpoint a single species, the fungal pathogen Candida glabrata, in which a trans mutation has occurred very recently in a single AP-1 family member distinguishing it from its Saccharomyces ortholog. Comparison of chromatin immunoprecipitation profiles between Candida and Saccharomyces shows that, despite their different DNA binding domains, the AP-1 orthologs regulate a conserved block of genes. This conservation is enabled by concomitant changes in the cis-regulatory motifs upstream of each gene. Thus, both trans and cis mutations have perturbed the yeast AP-1 regulatory system in such a way as to compensate for one another. This demonstrates an example of “co-evolution” between a DNA-binding transcription factor and its cis-regulatory site, reminiscent of the co-evolution of protein binding partners. 3 Experiments were performed. Three replicates CgAp1-TAP was ChIPped under MMS treatment (GSM397447..GSM397449), two replicates each of ScYap1R79K and ScYap4K252R (GSM594724..GSM594727), were ChIPped under MMS treatment.
Project description:Transcriptional networks have been shown to evolve very rapidly, prompting questions as to how such changes arise and are tolerated. Recent comparisons of transcriptional networks across species have implicated variations in the cis-acting DNA sequences near genes as the main cause of divergence. What is less clear is how these changes interact with trans-acting changes occurring elsewhere in the genetic circuit. Here, we report the discovery of a system of compensatory trans and cis mutations in the yeast AP-1 transcriptional network that allows for conserved transcriptional regulation despite continued genetic change. We pinpoint a single species, the fungal pathogen Candida glabrata, in which a trans mutation has occurred very recently in a single AP-1 family member distinguishing it from its Saccharomyces ortholog. Comparison of chromatin immunoprecipitation profiles between Candida and Saccharomyces shows that, despite their different DNA binding domains, the AP-1 orthologs regulate a conserved block of genes. This conservation is enabled by concomitant changes in the cis-regulatory motifs upstream of each gene. Thus, both trans and cis mutations have perturbed the yeast AP-1 regulatory system in such a way as to compensate for one another. This demonstrates an example of “co-evolution” between a DNA-binding transcription factor and its cis-regulatory site, reminiscent of the co-evolution of protein binding partners.
Project description:Gene expression differences between species are driven by both cis and trans effects. Whereas cis effects on gene expression are due to nearby genetic variants, trans effects are due to distal genetic variants that affect diffusible elements such as transcription factors. However, as previous studies have mostly assessed the impacts of cis and trans effects at the gene level, how cis and trans effects differentially impact regulatory elements such as enhancers and promoters remains poorly understood. Here, we used massively parallel reporter assays to directly measure cis and trans effects between human and mouse embryonic stem cells at thousands of individual regulatory elements, including enhancers as well as promoters of both protein-coding and long non-coding RNA genes. Our approach revealed that cis effects are widespread across regulatory elements, and the strongest cis effects are associated with the disruption of motifs recognized by strong transcriptional activators. Conversely, we found that trans effects are rare but stronger in enhancers than promoters, and can be attributed to a subset of transcription factors that are differentially expressed between human and mouse. While previous gene-based studies have found extensive co-occurrence of cis and trans effects in opposite directions that stabilize gene expression between species—or compensatory cis-trans effects—we find that cis-trans compensation is uncommon within individual regulatory elements. Moreover, regulatory elements that do show compensatory cis-trans effects are often less redundant than regulatory elements lacking compensatory cis-trans effects. Thus, our results are consistent with a model wherein compensatory cis-trans effects occur more often through crosstalk between multiple redundant regulatory elements than within a single individual regulatory element. Together, these results indicate that studying the evolution of individual regulatory elements is pivotal to understand the tempo and mode of gene expression evolution.
Project description:Variation in gene expression arises from cis- and trans-regulatory mutations, which contribute differentially to expression divergence. Here, we compare the impacts on gene expression and fitness for cis- and trans-regulatory mutations affecting expression of the TDH3 gene in Saccharomyces cerevisiae. We use the effects of cis-regulatory mutations to isolate effects of trans-regulatory mutations caused by impacts on TDH3 from pleiotropic impacts on other genes, providing a rare distribution of pleiotropic effects. These pleiotropic effects were often, but not always, deleterious. For cis- and trans-regulatory mutations with similar effects on TDH3, trans-regulatory mutations had more widespread effects on gene expression, with distinct impacts on expression of genes downstream of TDH3. These differences between cis-and trans-regulatory mutations help explain their different contributions to regulatory evolution.
Project description:Transcriptional networks have been shown to evolve very rapidly, prompting questions as to how such changes arise and are tolerated. Recent comparisons of transcriptional networks across species have implicated variations in the cis-acting DNA sequences near genes as the main cause of divergence. What is less clear is how these changes interact with trans-acting changes occurring elsewhere in the genetic circuit. Here, we report the discovery of a system of compensatory trans and cis mutations in the yeast AP-1 transcriptional network that allows for conserved transcriptional regulation despite continued genetic change. We pinpoint a single species, the fungal pathogen Candida glabrata, in which a trans mutation has occurred very recently in a single AP-1 family member, distinguishing it from its Saccharomyces ortholog. Comparison of chromatin immunoprecipitation profiles between Candida and Saccharomyces shows that, despite their different DNA-binding domains, the AP-1 orthologs regulate a conserved block of genes. This conservation is enabled by concomitant changes in the cis-regulatory motifs upstream of each gene. Thus, both trans and cis mutations have perturbed the yeast AP-1 regulatory system in such a way as to compensate for one another. This demonstrates an example of "coevolution" between a DNA-binding transcription factor and its cis-regulatory site, reminiscent of the coevolution of protein binding partners.
Project description:Gene expression evolution can be caused by changes in cis- or trans-regulatory elements or both. As cis and trans regulation operate through different molecular mechanisms, cis and trans mutations may show different inheritance patterns and may be subjected to different selective constraints. To investigate these issues, we obtained and analyzed gene expression data from two Saccharomyces cerevisiae strains and their hybrid, using high-throughput sequencing. Our data indicate that compared to other types of genes, those with antagonistic cis-trans interactions are more likely to exhibit over- or under-dominant inheritance of expression level. Moreover, in accordance with previous studies, genes with trans variants tend to have a dominant inheritance pattern while cis variants are enriched for additive inheritance. In addition, cis regulatory differences contribute more to expression differences between species than within species, whereas trans regulatory differences show a stronger association between divergence and polymorphism. Our data indicate that in the trans component of gene expression differences genes subjected to weaker selective constraints tend to have an excess of polymorphism over divergence compared to those subjected to stronger selective constraints. In contrast, in the cis component, this difference between genes under stronger and weaker selective constraint is mostly absent. To explain these observations, we propose that purifying selection more strongly shapes trans polymorphism than cis polymorphism. Study the gene expression patterns in two strains of yeast (BY and RM)
Project description:Gene expression evolution can be caused by changes in cis- or trans-regulatory elements or both. As cis and trans regulation operate through different molecular mechanisms, cis and trans mutations may show different inheritance patterns and may be subjected to different selective constraints. To investigate these issues, we obtained and analyzed gene expression data from two Saccharomyces cerevisiae strains and their hybrid, using high-throughput sequencing. Our data indicate that compared to other types of genes, those with antagonistic cis-trans interactions are more likely to exhibit over- or under-dominant inheritance of expression level. Moreover, in accordance with previous studies, genes with trans variants tend to have a dominant inheritance pattern while cis variants are enriched for additive inheritance. In addition, cis regulatory differences contribute more to expression differences between species than within species, whereas trans regulatory differences show a stronger association between divergence and polymorphism. Our data indicate that in the trans component of gene expression differences genes subjected to weaker selective constraints tend to have an excess of polymorphism over divergence compared to those subjected to stronger selective constraints. In contrast, in the cis component, this difference between genes under stronger and weaker selective constraint is mostly absent. To explain these observations, we propose that purifying selection more strongly shapes trans polymorphism than cis polymorphism.