Proteins that genetically interact with the Saccharomyces cerevisiae transcription factor Gal11p emphasize its role in the initiation-elongation transition

The GAL11 gene encodes a transcription factor that is a component of the SR B/Mediator subcomplex of the RNA polymerase II holoenzyme in the yeast Sacc haromyces cerevisiae.. In agreement with this biochemical characterization, Gal11p has been found to be required for optimal production of mRNA from m any yeast promoters, and recessive mutations in GAL11 have been shown to ca use pleiotropic defects. Despite this progress, the role of Gal11p in gene regulation remains largely unknown. In a multicopy suppressor analysis of a gal11 Delta mutation we have identified genes encoding proteins that are p art of, or can interact with, the RNA polymerase II transcription complex, as well as factors involved in cell cycle regulation. Among the suppressors that are clearly related to the transcriptional apparatus, Gal11p genetica lly interacts with components of the SRB/Mediator complex, as well as with factors such as TFIIE and TFIIH that are required for promoter clearance an d transcription elongation by RNA polymerase II. These findings, taken toge ther with published results of biochemical and genetic analyses, suggest a role for Gal11p at the interface between the SRB/Mediator complex and the g eneral transcription factors TFIIE and TFIIH, which modulate, via phosphory lation of the CTD, the activity of the RNA polymerase.