FIG. 10.

Model for proteasome-chaperone interaction at the MMTV template and association with transcription. Liganded GR binding to MMTV ultimately leads to initiation complex formation. Formation of the complex may be enhanced by longer GR residence at the MMTV template. The duration of GR occupancy at the template is determined in part by competition between proteasome and chaperone functions. Proteasome inhibition favors GR occupancy, leading to a slower FRAP with an immobile fraction. Chaperone inhibition by geldanamycin favors GR loss, leading to a faster FRAP. The equilibrium between these two components helps to set the transcriptional level and may be mediated in part by one or more factors that are known to couple chaperone and proteasome activities (5, 21).