FIG. 9.

Transcriptional regulation by Ume6, nuclear hormone receptors, and Myc/Mad/Max. DNA-binding proteins (Ume6, nuclear hormone receptors [NHR], or Max heterodimer) in conjunction with cis-acting DNA elements (e.g., URS1, hormone response element [HRE], or E box, as indicated), repress transcription through interaction with a corepressor complex containing Sin3, Rpd3, and additional proteins (not all are shown). In each system, the switch from repression to activation requires that the Sin3 corepressor complex be replaced by an activation complex. In meiosis, this involves the binding of Ime1. For NHR, this involves binding of hormone and a number of potential coactivators (not all are shown) including histone acetylases (HAT) (see references 26, 31, and 82 for reviews). For Max, it involves heterodimerization with Myc, which possesses a transactivation domain that may act through a variety of additional proteins (14, 31, 58).