The structural and functional role of Med5 in the yeast mediator tail module

Med5 (Nut1) is identified here as a component of the Mediator tail region. Med5 is positioned peripherally to Med16 (Sin4) together with the three members of the putative Gal11 module, Med15 (Gal11), Med2, and Med3 (Pgd1). The biochemical analysis receives support from genetic interactions between med5 Delta and med15 Delta deletions. The med5 Delta and med16 Delta deletion strains share many phenotypes, including effects on mitochondrial function with enhanced growth on nonfermentable carbon sources, increased citrate synthase activity, and increased oxygen consumption. Deletion of the MED5 gene leads to increased transcription of nuclear genes encoding components of the oxidative phosphorylation machinery, whereas mitochondrial genes encoding components of the same machinery are down-regulated. We discuss a possible role for Med5 in coordinating nuclear and mitochondrial gene transcription.