Phosphorylation of a nuclear condensate regulates cohesion and mRNA retention.

Nuclear speckles are membraneless organelles that associate with active transcription sites and participate in post-transcriptional mRNA processing. During the cell cycle, nuclear speckles dissolve following phosphorylation of their protein components. Here, we identify the PP1 family as the phosphatases that counteract kinase-mediated dissolution.

DYRK3 enables secretory trafficking by maintaining the liquid-like state of ER exit sites.

The dual-specificity kinase DYRK3 controls the formation and dissolution of multiple biomolecular condensates, regulating processes including stress recovery and mitotic progression. Here, we report that DYRK3 functionally interacts with proteins associated with endoplasmic reticulum (ER) exit sites (ERESs) and that inhibition of DYRK3 perturbs the organization of the ERES-Golgi interface and secretory trafficking. DYRK3-mediated regulation of ERES depends on the N-terminal intrinsically disordered region (IDR) of the peripheral membrane protein SEC16A, which co-phase separates with ERES components to form liquid-like condensates on the surface of the ER.

Kinase-controlled phase transition of membraneless organelles in mitosis.

Liquid-liquid phase separation has been shown to underlie the formation and disassembly of membraneless organelles in cells, but the cellular mechanisms that control this phenomenon are poorly understood. A prominent example of regulated and reversible segregation of liquid phases may occur during mitosis, when membraneless organelles disappear upon nuclear-envelope breakdown and reappear as mitosis is completed. Here we show that the dual-specificity kinase DYRK3 acts as a central dissolvase of several types of membraneless organelle during mitosis.

Tug-of-war between dissimilar teams of microtubule motors regulates transport and fission of endosomes.

Intracellular transport is interspersed with frequent reversals in direction due to the presence of opposing kinesin and dynein motors on organelles that are carried as cargo. The cause and the mechanism of reversals are unknown, but are a key to understanding how cargos are delivered in a regulated manner to specific cellular locations. Unlike established single-motor biophysical assays, this problem requires understanding of the cooperative behavior of multiple interacting motors.