ETAA1 (Ewing's tumor-associated antigen 1), also known as ETAA16, is a 926 amino acid cytoplasmic protein that is highly expressed in kidney, brain, liver and Ewing tumor cell lines. ETAA1 undergoes post-translational phosphorylation following DNA damage, most likely by either ATM or ATR, and is suggested to function as a tumour-specific cell surface antigen in Ewing's family of tumour cell lines. The gene encoding ETAA1 maps to human chromosome 2, which consists of 237 million bases, encodes over 1,400 genes and makes up approximately 8% of the human genome. A number of genetic diseases are linked to genes on chromosome 2 including Harlequin icthyosis, sitosterolemia and Alstrom syndrome.