Fig. 6. An action model of the mediator-related proteins in yeast and C. elegans: the MED-6-containing mediator complex as a convergence point of transcriptional regulation. (A) In yeast, yeast-specific mediator proteins such as Gal11 and Hrs1 relay signals from transcription activators through the universally conserved mediator complex that contains MED-6 to the general transcription factors to regulate transcription. (B) In the nematode vulval development pathway, SUR-2 is a metazoan-specific mediator-related protein that interacts with outside signals (activated by EGF) and relays them through the conserved mediator complex containing MED-6 to the general transcription factors that regulate genes associated with the Ras pathway. The SynMuv proteins including the histone deacetylase complex proteins may counteract the mediator functions. (C) In the nematode ray developmental pathway, SOP-1 is a mediator-related protein that represses the Wnt-mediated transcriptional activation, which is dependent on the universally conserved mediator complex that contains MED-6.