Necessary for the fragmentation of Golgi stacks during mitosis and for their reassembly after mitosis. Involved in the formation of the nuclear envelope, and of the transitional endoplasmic reticulum (tER). The transfer of membranes from the endoplasmic reticulum to the Golgi apparatus occurs via 50-70 nm transition vesicles which derive from part-rough, part-smooth transitional elements of the endoplasmic reticulum (tER). Vesicle budding from the tER is an ATP-dependent process. Involved in endoplasmic reticulum stress-induced pre-emptive quality control, a mechanism that selectively attenuates the translocation of newly synthesized proteins into the endoplasmic reticulum and reroutes them to the cytosol for proteasomal degradation. Plays a role in the regulation of stress granules (SGs) clearance process upon arsenite-induced response (By similarity). Also involved in DNA damage response: recruited to double-strand breaks (DSBs) sites and promotes the recruitment of tp53bp1 at DNA damage sites (By similarity). Together with sprtn metalloprotease, involved in the repair of covalent DNA-protein cross-links (DPCs) during DNA synthesis (By similarity). Involved in interstrand cross-link repair in response to replication stress by mediating unloading of the ubiquitinated CMG helicase complex (By similarity). Enhances cell cycle progression and inhibits apoptosis at low temperatures (By similarity). Essential for the maturation of ubiquitin-containing autophagosomes and the clearance of ubiquitinated protein by autophagy (By similarity). Acts as a negative regulator of type I interferon production by promoting ubiquitination of ddx58/rig-i (By similarity). May play a role in the ubiquitin-dependent sorting of membrane proteins to lysosomes where they undergo degradation (By similarity). May more particularly play a role in caveolins sorting in cells (By similarity). By controlling the steady-state expression of the IGF1R receptor, indirectly regulates the insulin-like growth factor receptor signaling pathway (By similarity). ATP + H2O = ADP + H(+) + phosphate ATPase activity is inhibited or reduced by lowering pH from 9.0 to 7.0, and by addition of Ca(2+), EDTA, KNO(3) or by treatment with N-ethylmaleimide (NEM). Homohexamer. Forms a ring-shaped particle of 12.5 nm diameter, that displays 6-fold radial symmetry. Interacts with the FACT/DUF complex, which includes subunits ssrp1/duf87 and supt16h/duf140 (By similarity). Phosphorylated. Belongs to the AAA ATPase family.