Med15: Glutamine-Rich Mediator Subunit with Potential for Plasticity. Issue 9 (September 2019)

• Record Type: Journal Article
• Authors: Cooper, David G.; Fassler, Jan S.
• Is Part Of: Trends in biochemical sciences. Volume 44:Issue 9(2019)
• Page Start: 737
• Page End: 751
• Publication Date: 2019-09
• Subjects: Gal11 -- polyglutamine -- low complexity -- domestication -- adaptation; Biochemistry -- Periodicals; 572
• DOI: 10.1016/j.tibs.2019.03.008
• Languages: English
• ISSNs: 0968-0004

Abstract

Abstract : The Mediator complex is required for basal activity of the RNA polymerase (Pol) II transcriptional apparatus and for responsiveness to some activator proteins. Med15, situated in the Mediator tail, plays a role in transmitting regulatory information from distant DNA-bound transcription factors to the transcriptional apparatus poised at promoters. Yeast Med15 and its orthologs share an unusual, glutamine-rich amino acid composition. Here, we discuss this sequence feature and the tendency of polyglutamine tracts to vary in length among strains of Saccharomyces cerevisiae, and we propose that different polyglutamine tract lengths may be adaptive within certain domestication habitats. Highlights: With the benefit of insight from over 1000 completed genome sequences from different yeast strains that are now archived in sequence databases, it has become clear that there is substantial variation within glutamine-rich regions of the yeast proteome. The ecological diversity of sequenced yeast genomes including yeast from wine, beer, biofuel, food, and clinical and laboratory settings, among others, provides an opportunity to evaluate correlations in variant polyglutamine alleles and specific domestication traits. In general, the subunits of the tail module of the RNA Pol II mediator complex are fast evolving. This property may be important for contacting species-specific transcription factors. Like many large complexes upon which eukaryotic cells rely, the subunit composition of the RNA Pol II mediator complex varies with the organism and, in animals there is variation in different cell types. Specialized complexes may have specific functions in gene expression that are not yet fully understood. Here, we raise the possibility that additional levels of specialization might be afforded by variation in Q tract length and other low-complexity regions found in mediator subunits.