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. DDI1 is a 396 amino acid protein that contains one ubiquitin-like domain. The gene encoding DDI1 maps to human chromosome 11, which makes up around 4% of human genomic DNA and is considered a gene and disease association dense chromosome. The chromosome 11 encoded Atm gene is important for regulation of cell cycle arrest and apoptosis following double strand DNA breaks. Atm mutation leads to the disorder known as ataxia-telangiectasia. The blood disorders Sickle cell anemia and β thalassemia are caused by HBB gene mutations. Wilms' tumors, WAGR syndrome and Denys-Drash syndrome are associated with mutations of the WT1 gene.