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Updated: Aug 12, 2026

Promoter Capture Hi-C: High-resolution, Genome-wide Profiling of Promoter Interactions
Published on: June 28, 2018
Structure and function of CRSP/Med2; a promoter-selective transcriptional coactivator complex
Dylan J Taatjes1, Robert Tjian
1Howard Hughes Medical Institute, Department of Molecular and Cell Biology, 401 Barker Hall, University of California-Berkeley, Berkeley, CA 94720, USA.
Abstract:
The multi-subunit, human CRSP coactivator-also known as Mediator (Med)-regulates transcription by mediating signals between enhancer-bound factors (activators) and the core transcriptional machinery. Interestingly, different activators are known to bind distinct subunits within the CRSP/Med complex. We have isolated a stable, endogenous CRSP/Med complex (CRSP/Med2) that specifically lacks both the Med220 and the Med70 subunits. The three-dimensional structure of CRSP/Med2 was determined to 31 A resolution using electron microscopy and single-particle reconstruction techniques. Despite lacking both Med220 and Med70, CRSP/Med2 displays potent, activator-dependent transcriptional coactivator function in response to VP16, Sp1, and Sp1/SREBP-1a in vitro using chromatin templates. However, CRSP/Med2 is unable to potentiate activated transcription from a vitamin D receptor-responsive promoter, which requires interaction with Med220 for coactivator recruitment, whereas VDR-directed activation by CRSP/Med occurs normally. Thus, it appears that CRSP/Med may be regulated by a combinatorial assembly mechanism that allows promoter-selective function upon exchange of specific coactivator targets.
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