The ubiquitin ligase HACE1 regulates Golgi membrane dynamics during the cell cycle

Partitioning of the Golgi membrane into daughter cells during mammalian cell division occurs through a unique disassembly and reassembly process that is regulated by ubiquitination. However, the identity of the ubiquitin Ligase is unknown. Here we show that the Homologous to the E6-AP Carboxyl Terminus (HECT) domain containing ubiquitin Ligase HACE1 is targeted to the Golgi membrane through interactions with Rab proteins. The ubiquitin Ligase activity of HACE1 in mitotic Golgi disassembly is required for subsequent postmitotic Golgi membrane fusion. Depletion of HACE1 using small interfering RNAs or expression of an inactive HACE1 mutant protein in cells impaired postmitotic Golgi membrane fusion. The identification of HACE1 as a Golgi-localized ubiquitin Ligase provides evidence that ubiquitin has a critical role in Golgi biogenesis during the cell cycle.