This family includes the eukaryotic tumor susceptibility gene 101 protein (TSG101). Altered transcripts of this gene have been detected in sporadic breast cancers and many other human malignancies. However, the involvement of this gene in neoplastic transformation and tumorigenesis is still elusive. TSG101 is required for normal cell function of embryonic and adult tissues but that this gene is not a tumor suppressor for sporadic forms of breast cancer. This family is related to the ubiquitin conjugating enzymes.