Properties of repression condensates in living Ciona embryos. Author Nicholas Treen, Shunsuke Shimobayashi, Jorine Eeftens, Clifford Brangwynne, Michael Levine Publication Year 2021 Type Journal Article Abstract Recent studies suggest that transcriptional activators and components of the pre-initiation complex (PIC) form higher order associations-clusters or condensates-at active loci. Considerably less is known about the distribution of repressor proteins responsible for gene silencing. Here, we develop an expression assay in living Ciona embryos that captures the liquid behavior of individual nucleoli undergoing dynamic fusion events. The assay is used to visualize puncta of Hes repressors, along with the Groucho/TLE corepressor. We observe that Hes.a/Gro puncta have the properties of viscous liquid droplets that undergo limited fusion events due to association with DNA. Hes.a mutants that are unable to bind DNA display hallmarks of liquid-liquid phase separation, including dynamic fusions of individual condensates to produce large droplets. We propose that the DNA template serves as a scaffold for the formation of Hes condensates, but limits the spread of transcriptional repressors to unwanted regions of the genome. Journal Nature communications Volume 12 Issue 1 Pages 1561 Date Published 03/2021 ISSN Number 2041-1723 DOI 10.1038/s41467-021-21606-5 Alternate Journal Nat Commun PMCID PMC7946874 PMID 33692345 PubMedPubMed CentralGoogle ScholarBibTeXEndNote X3 XML