Heterogenous organization in condensates of multiple transcription factors in embryonic stem cells

Biomolecular condensates formed via liquid-liquid phase separation are ubiquitous in cells, especially in the nucleus. While condensates containing one or two kinds of biomolecules have been relatively well characterized, those with more hetero-genous biomolecular components and interactions between biomolecules inside are largely unknown. This study used resi-due-resolution molecular dynamics simulations to investigate heterogeneous protein assemblies that include four master tran-scription factors in mammalian embryonic stem cells: Oct4, Sox2, Klf4, and Nanog. Simulations of the mixture systems showed highly heterogeneous and dynamic behaviors; the condensates mainly contained Sox2, Klf4, and Nanog, while Oct4 was dissolved into the dilute phase. Condensates consisted of loosely interacting clusters in which Klf4 was the most abun-dant in the cores. We suggest that Klf4 serves as a scaffold of the condensate where Sox2 and Nanog are bound to stabilize the condensate, whereas Oct4 is moderately recruited to the condensate, serving as a client mainly via its interaction with Sox2.