Structural Characterization of the SMRT Corepressor Interacting with Histone Deacetylase 7

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• SMRT (Silencing Mediator for Retinoid and Thyroid hormone Receptor) is a large, intrinsically disordered protein acting as a scaffold.
• SMRT coordinates transcription factors and chromatin modifiers, including Class I and IIa histone deacetylases (HDACs).
• HDAC7, a Class IIa deacetylase, interacts with the SMRT corepressor complex.

Purpose of the Study:

• To characterize the interaction between SMRT and HDAC7 at a molecular level.
• To identify the specific binding site and interaction mechanism between SMRT and HDAC7.

Main Methods:

• Random library screening to generate soluble SMRT fragments.
• Nuclear Magnetic Resonance (NMR) spectroscopy to characterize SMRT fragments and map binding sites.
• Truncation and alanine mutagenesis for detailed binding site analysis and confirmation.

Main Results:

• Identified intrinsically disordered SMRT fragments, including residues 1255-1452, that bind HDAC7 with micromolar affinity.
• Mapped the SMRT binding site to a 28-residue region containing a glycine-serine-isoleucine (GSI) motif and an alpha helix.
• Demonstrated that HDAC7 binds this SMRT region via its surface zinc ion binding site.

Conclusions:

• The intrinsically disordered nature of SMRT facilitates its role as a versatile protein interaction hub.
• Detailed characterization of the SMRT-HDAC7 interaction provides insights into the regulation of gene expression by Class IIa deacetylases.
• The identified 28-residue binding motif represents a key interaction interface for HDAC7 within the SMRT corepressor complex.