The cofactor complexes such as ARC (activator-recruited cofactor) and CRSP (cofactor required for Sp1) share several common subunits and mediate interactions between activators and the basal transcription apparatus. Taatjes et al. (see the Perspective by Meisterernst), using biochemical assays and electron microscopy, found that the larger complex, ARC, is composed of two multisubunit complexes, ARC-L and CRSP, and that transcriptional activity is only observed with CRSP. Structural determinations indicate that distinct conformations are induced in the CRSP complex by various activators. Therefore, different activators may allow for different transcriptional readouts based on the specific conformations that form.
M. Meisterernst, Mediator meets Morpheus. Science 295, 984-985 (2002). [Full Text]