Structural and functional details of the N-terminal activation function 1 (AF1) of most nuclear receptors are poorly understood due to the highly dynamic intrinsically disordered nature of this domain. A hydrogen/deuterium exchange (HDX) mass-spectrometry-based investigation of TATA box-binding protein (TBP) interaction with various domains of progesterone receptor (PR) demonstrate that agonist-bound PR interaction with TBP via AF1 impacts the mobility of the C-terminal AF2. Results from HDX and other biophysical studies involving agonist- and antagonist-bound full-length PR and isolated PR domains reveal the molecular mechanism underlying synergistic transcriptional activation mediated by AF1 and AF2, dominance of PR-B isoform over PR-A, and the necessity of AF2 for full AF1-mediated transcriptional activity. These results provide a comprehensive picture elaborating the underlying mechanism of PR-TBP interactions as a model for studying nuclear receptor (NR)-transcription factor functional interactions.
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