Notch1 forms nuclear transcriptional condensates that drive target gene expression

The Notch receptor is a titratable, context-specific counter of intercellular interactions that translates productive interactions with ligands on neighbouring cells into corresponding changes in gene expression via the nuclear localization of the Notch intracellular Domain (NICD). Using an Optogenetic Notch1 construct in combination with a live imaging transcriptional reporter and super-resolution imaging, we show that the N1ICD activates gene expression through spontaneous self-assembly into transcriptional condensates whose phase separation is driven by C-terminal Intrinsically Disordered Regions (IDR) of the N1ICD. N1ICD condensates recruit and encapsulate a broad set of core transcriptional proteins, thereby facilitating gene expression and promoting super enhancer-looping. We produced a model of Notch1 activity, whereby discrete changes in nuclear NICD abundance is translated into precise changes in target gene expression through the assembly of phase separated N1ICD ‘molecular crucibles’ that catalyze gene expression in a concentration-dependent manner by enriching essential transcriptional machineries at target genomic loci. ### Competing Interest Statement The authors have declared no competing interest.