Golgi membranes are absorbed into and reemerge from the ER during mitosis

Quantitative imaging and photobleaching were used to measure ER/Golgi recyc ling of GFP-tagged Golgi proteins in interphase cells and to monitor the di ssolution and reformation of the Golgi during mitosis. In interphase, recyc ling occurred every 1.5 hr, and blocking ER egress trapped cycling Golgi en zymes in the ER with loss of Golgi structure. In mitosis, when ER export st ops, Golgi proteins redistributed into the ER as shown by quantitative imag ing in vivo and immuno-EM. Comparison of the mobilities of Golgi proteins a nd lipids ruled out the persistence of a separate mitotic Golgi vesicle pop ulation and supported the idea that all Golgi components are absorbed into the ER. Moreover, reassembly of the Golgi complex after mitosis failed to o ccur when ER export was blocked. These results demonstrate that in mitosis the Golgi disperses and reforms through the intermediary of the ER, exploit ing constitutive recycling pathways. They thus define a novel paradigm for Golgi genesis and inheritance.