Analysis of Polygenic Mutants Suggests a Role for Mediator in Regulating Transcriptional Activation Distance in Saccharomyces cerevisiae.
Studies of natural populations of many organisms have shown that traits are often complex, caused by contributions of mutations in multiple genes. In contrast, genetic studies in the laboratory primarily focus on studying the phenotypes caused by mutations in a single gene. However, the single mutation approach may be limited with respect to the breadth and degree of new phenotypes that can be found. We have taken the approach of isolating complex, or polygenic mutants in the lab to study the regulation of transcriptional activation distance in yeast. While most aspects of eukaryotic transcription are conserved from yeast to human, transcriptional activation distance is not. In Saccharomyces cerevisiae, the upstream activating sequence (UAS) is generally found within 450 base pairs of the transcription start site (TSS) and when the UAS is moved too far away, activation no longer occurs. In contrast, metazoan enhancers can activate from as far as several hundred kilobases from the TSS. Previously, we identified single mutations that allow transcription activation to occur at a greater-than-normal distance from the GAL1 UAS. As the single mutant phenotypes were weak, we have now isolated polygenic mutants that possess strong long-distance phenotypes. By identification of the causative mutations we have accounted for most of the heritability of the phenotype in each strain and have provided evidence that the Mediator coactivator complex plays both positive and negative roles in the regulation of transcription activation distance.
Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115.
Caitlin T
CT
Reavey
Department of Biological Sciences, Rowan University, Glassboro, New Jersey 08028.
Mark J
MJ
Hickman
Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115.
Krista C
KC
Dobi
Lewis-Sigler Institute and Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544.
David
D
Botstein
Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115 winston@genetics.med.harvard.edu.
Fred
F
Winston
D004268:DNA-Binding Proteins / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D056892:Mediator Complex / Q000235:genetics*; D009154:Mutation; D010641:Phenotype; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics; D024363:Transcription Initiation Site; D014158:Transcription, Genetic; D015533:Transcriptional Activation / Q000235:genetics*
D004268:DNA-Binding Proteins; D056892:Mediator Complex
Mediator; Saccharomyces cerevisiae; polygenic; transcription