Unexpected specificity within dynamic transcriptional protein-protein complexes.

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• Eukaryotic gene activation relies on dynamic protein-protein interactions between transcriptional activators and coactivators.
• Existing models suggest nonspecific interactions mediate activator-coactivator binding, contrasting with tightly regulated transcription.

Purpose of the Study:

• To investigate the molecular recognition mechanisms between the ETV/PEA3 family of activators and the coactivator Med25.
• To elucidate how sequence variations in activators affect complex formation and binding affinity.
• To challenge existing models by proposing a new molecular recognition paradigm for disordered proteins.

Main Methods:

• Mechanistic dissection of activator-coactivator complexes.
• Biochemical and biophysical analyses of protein-protein interactions.
• Conformational ensemble analysis of dynamic complexes.

Main Results:

• Small sequence variations in activators significantly alter the conformational ensemble of the activator-coactivator complex without changing overall binding affinity.
• Distal residues of the activator play a crucial role in mediating conformational redistribution.
• Specific contacts direct the ETV/PEA3•Med25 ensembles, facilitated by structural shifts in the Med25 binding interface.

Conclusions:

• Coactivator plasticity is critical for recognizing disordered activators.
• Molecular recognition models for disordered proteins must incorporate the binding partner's role in mediating specificity.
• This study reveals a nuanced model of molecular recognition in gene activation.