Golgi ribbon disassembly in mitosis. (a) During interphase, the Golgi stacks are interconnected into a ribbon that is localized close to the centrosomes. In late G2, the lateral connections between stacks are severed, which unlinks the ribbon and allows progression into mitosis. The cisternae then further unstack and vesiculate. Upon partitioning with the aid of the spindle, the mitotic Golgi membranes reassemble a ribbon in both daughter cells. (b) Stages and main players in mitotic Golgi disassembly. Ribbon unlinking in late G2 requires the membrane fission protein BARS and the phosphorylation of GRASP65 and GRASP55. Once the cells entered mitosis, further phosphorylation of GRASP 65 and GRASP55 induces cisternal unstacking. Simultaneously the cisternae vesiculate due to inhibition of both vesicle tethering (mediated by phosphorylation of GM130) and heterotypic fusion (mediated by ubiquitination of the t-SNARE syntaxin 5). Meanwhile, homotypic fusion of Golgi membranes is also blocked by phosphorylation of the p97 adaptors p37 and p47 and the co-factor VCIP135.