UBE20, also known as E2-230K, is a 1,292 amino acid member of the uniquitin-conjugating enzyme family that is involved in protein modification. Expressed predominately in heart and skeletal muscle, UBE2O functions to catalyze the ATP-dependent covalent attachment of ubiquitin to select proteins, thereby targeting the ubiquitinated proteins for proteasomal degradation. The gene encoding UBE2O maps to human chromosome 17, which comprises over 2.5% of the human genome and encodes over 1,200 genes. Two key tumor suppressor genes are associated with chromosome 17, namely, p53 and BRCA1. Tumor suppressor p53 is necessary for maintenance of cellular genetic integrity by moderating cell fate through DNA repair versus cell death. Malfunction or loss of p53 expression is associated with malignant cell growth and Li-Fraumeni syndrome. Like p53, BRCA1 is directly involved in DNA repair, though specifically it is recognized as a genetic determinant of early onset breast cancer and predisposition to cancers of the ovary, colon, prostate gland and fallopian tubes.