Notch1 Phase Separation Coupled Percolation facilitates target gene expression and enhancer looping.

Area of Science:

• Cell Biology
• Molecular Biology
• Gene Regulation

Background:

• The Notch receptor pathway is crucial for cell communication and gene expression.
• Notch signaling involves the nuclear translocation of the Notch intracellular Domain (NICD).
• Mechanisms regulating NICD's role in gene expression are not fully understood.

Purpose of the Study:

• To investigate the role of NICD in gene expression regulation.
• To elucidate the physical state and function of NICD within the nucleus.
• To understand how NICD influences transcriptional machinery and target gene activation.

Main Methods:

• Immunohistochemistry
• RNA in situ hybridization
• Optogenetics
• Super-resolution live imaging of transcription in human cells

Main Results:

• N1ICD forms nuclear condensates that facilitate Notch target gene expression.
• N1ICD undergoes Phase Separation Coupled Percolation (PSCP) into transcriptional condensates.
• These condensates recruit and enrich core transcriptional proteins, promoting MYC protooncogene expression and enhancer-looping.

Conclusions:

• NICD forms transcriptional condensates via Phase Separation Coupled Percolation (PSCP).
• The intrinsically disordered transcriptional activation domain of N1ICD drives condensate formation.
• This novel mechanism highlights how NICD abundance changes translate into transcriptional condensate assembly for gene expression.