RNA scaffolds the Golgi ribbon by forming condensates with GM130

Abstract

The mammalian Golgi apparatus is composed of stacks of cisternae that are laterally linked to form a continuous ribbon like structure, but the molecular mechanisms that maintain the Golgi ribbon remain unclear. Here, we show that ribbon formation is mediated by biomolecular condensates of RNA and the Golgi resident protein GM130. We identified GM130 as a membrane-bound RNA binding protein at the Golgi. Acute degradation of either RNA or GM130 in cells disrupted the Golgi ribbon. Under stress conditions, RNA was displaced from GM130 and the ribbon was disjoint, which was restored after cells recovered from stress. When overexpressed in cells, GM130 formed RNA-dependent liquid-like condensates. GM130 contains an intrinsically disordered domain at its N-terminus, which was sufficient to recruit RNA to drive condensate assembly in vitro. Condensates of the N-terminal domain of GM130 and RNA were sufficient to link purified rat liver Golgi membranes which is a reconstruction of aspects of lateral linking of stacks into a ribbon-like structure. Together, these studies reveal that biomolecular condensates of GM130-RNA scaffold the Golgi ribbon.