Light-activated macromolecular phase separation modulates transcription by reconfiguring chromatin interactions

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Biomolecular condensates are crucial for regulating gene transcription.
• The precise link between nuclear condensation and transcriptional activation is not fully understood.

Purpose of the Study:

• To develop an optogenetic method for inducible control and analysis of nuclear condensates.
• To investigate the role of nuclear condensation in gene transcription and chromatin organization.

Main Methods:

• Developed light-activated macromolecular phase separation (LAMPS), a biotinylated CRISPR-dCas9-based optogenetic tool.
• Utilized LAMPS for inducible condensate formation, affinity purification, and multiomic analysis at targeted genomic loci.
• Analyzed chromatin accessibility, chromosomal loop formation, and proteomic composition of light-induced condensates.

Main Results:

• LAMPS successfully induced nuclear condensate formation at enhancers and promoters, activating endogenous gene transcription.
• Condensation led to chromatin reconfiguration, increased accessibility, and de novo formation of long-range chromosomal loops.
• Proteomic profiling identified enrichment of transcriptional coactivators and chromatin proteins within light-induced condensates.

Conclusions:

• Nuclear condensate formation at genomic loci reconfigures chromatin architecture and protein assemblies to modulate gene transcription.
• LAMPS provides a powerful tool for mechanistic studies of nuclear condensation, genome structure, and gene transcription in live cells.