Structural and Functional Studies of the RBPJ-SHARP Complex Reveal a Conserved Corepressor Binding Site

Area of Science:

• Molecular Biology
• Developmental Biology
• Cell Signaling

Background:

• The Notch signaling pathway is crucial for metazoan development and homeostasis.
• Dysregulation of Notch signaling is implicated in various human diseases.
• The transcription factor RBPJ plays a key role in mediating Notch-induced gene expression changes.

Purpose of the Study:

• To elucidate the structural basis of RBPJ's repressor function.
• To understand the interaction between RBPJ, the corepressor SHARP, and DNA.
• To validate the role of SHARP binding in RBPJ-mediated transcriptional repression.

Main Methods:

• X-ray crystallography to determine the structure of RBPJ bound to SHARP and DNA.
• Site-directed mutagenesis to create structure-based mutants of RBPJ.
• Biophysical and biochemical assays to assess protein interactions.
• Cellular assays to evaluate transcriptional repression activity.

Main Results:

• The crystal structure of RBPJ bound to SHARP and DNA was determined, revealing the binding interface.
• Structure-based mutants deficient in SHARP binding were generated.
• These mutants failed to repress Notch-responsive gene transcription in cellular assays.
• Biophysical and biochemical data confirmed the importance of the RBPJ-SHARP interaction for repression.

Conclusions:

• The structure of RBPJ-SHARP-DNA complex provides mechanistic insights into transcriptional repression.
• SHARP binding is essential for RBPJ's function as a repressor in Notch signaling.
• These findings deepen our understanding of Notch pathway regulation and its role in disease.