CDC2 KINASE DIRECTLY PHOSPHORYLATES THE CIS-GOLGI MATRIX PROTEIN GM130 AND IS REQUIRED FOR GOLGI FRAGMENTATION IN MITOSIS

Mitotic fragmentation of the Golgi apparatus can be largely explained by disruption of the interaction between GM130 and the vesicle-docking protein p115. Here we identify a single serine (Ser-25) in GM130 as t he key phosphorylated target and Cdc2 as the responsible kinase. MEK1, a component of the MAP kinase signaling pathway recently implicated i n mitotic Golgi fragmentation, was not required for GM130 phosphorylat ion or mitotic fragmentation either in vitro or in vivo. We propose th at Cdc2 is directly involved in mitotic Golgi fragmentation and that s ignaling via MEK1 is not required for this process.