TOR1AIP2 encodes LULL1, a transmembrane protein essential for endoplasmic reticulum (ER) integrity and nuclear envelope architecture 1. LULL1 functions as a cofactor that activates TorsinA and related torsin family ATPases through an active site complementation mechanism, wherein a conserved arginine residue in LULL1 comes into close proximity with nucleotides bound in neighboring Torsin subunits 2. Unlike LAP1 which localizes to the inner nuclear membrane, LULL1 resides in the peripheral ER but paradoxically targets TorsinA to the inner nuclear membrane through activity-dependent mechanisms requiring LULL1-mediated oligomerization and transient disassembly of TorsinA complexes 3. TOR1AIP2 mutations cause dystonia with hemichorea/hemiballism; identified variants (p.Arg412Gly and p.Gln338His) disrupt the TorsinA-LULL1 binding interface, resulting in weaker protein interaction similar to DYT1 dystonia caused by TOR1A mutations 1. LULL1 is also required for efficient herpes simplex virus 1 replication, with LULL1 knockout reducing viral genome accumulation tenfold 4. These findings establish TOR1AIP2 as a critical regulator of torsin ATPase activity with implications for movement disorders and viral pathogenesis.