DDI1 and DDI2 are ubiquitin receptor homologs of the Saccharomyces cerevisiae ddi1 protein, which is involved in regulation of the cell cycle and the late secretory pathway. DDI2 is a 399 amino acid protein that contains one ubiquitin-like domain and exists as three isoforms as a result of alternative splicing. The gene encoding DDI2 maps to human chromosome 1, the largest human chromosome which spans about 260 million base pairs and makes up 8% of the human genome. Other notable genes located on chromosome 1 include LMNA, which is associated with the rare aging disease Hutchinson-Gilford progeria, and the MUTYH gene, which is partially responsible for familial adenomatous polyposis. Stickler syndrome, Parkinsons, Gaucher disease and Usher syndrome.