Keeping notch target genes off: a CSL corepressor caught in the act

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• The Notch signaling pathway is crucial for cell development and differentiation.
• CSL (CBF1/RBPJ) is a key transcription factor in the Notch pathway, acting as a molecular switch.
• Understanding CSL's interactions is vital for deciphering Notch signaling regulation.

Purpose of the Study:

• To elucidate the structural basis of CSL-corepressor interaction.
• To compare the binding of KyoT2 to CSL with that of the Notch RAM domain.
• To gain insights into the mechanism of CSL's switch from activator to repressor.

Main Methods:

• X-ray crystallography to determine the structure of CSL bound to KyoT2.
• Biochemical assays to characterize the interaction interface.
• Comparative structural analysis.

Main Results:

• The crystal structure of CSL complexed with the corepressor KyoT2 was determined.
• KyoT2 binds to CSL in a conformationally distinct manner compared to the Notch RAM domain.
• The structural data provides a molecular explanation for CSL's transition between transcriptional activation and repression.

Conclusions:

• The structure of CSL-KyoT2 complex reveals a novel binding mode that facilitates repression.
• Differences in KyoT2 and Notch RAM domain binding explain CSL's context-dependent function.
• This study offers a structural foundation for understanding Notch pathway regulation by CSL.