LULL1 is a 470 amino acid endoplasmic reticulum single-pass membrane protein belonging to the TOR1AIP family. LULL1 interacts with torsinA, an essential AAA+ ATPase found in the endoplasmic reticulum (ER) and nuclear envelope (NE) of higher eukaryotes. LULL1 regulates the distribution and activity of torsinA within the ER and NE lumen and reveals functional defects in mutant torsinA, which is responsible for DYT1 dystonia, a neurodevelopmental disease caused by an in-frame deletion (Deltagag) in the gene encoding torsinA. The gene encoding LULL1 maps to human chromosome 1, which spans 260 million base pairs, contains over 3,000 genes and comprises nearly 8% of the human genome.