The RING-type zinc finger motif is present in a number of viral and eukaryotic proteins and is made of a conserved cysteine-rich domain that is able to bind two zinc atoms. Proteins that contain this conserved domain are generally involved in the ubiquitination pathway of protein degradation. TRAC-1 (T-cell RING activation protein 1), also known as RNF125 (ring finger protein 125) or E3 ubiquitin-protein ligase RNF125, is a 232 amino acid novel E3 ubiquitin ligase that functions as a positive regulator in the T-cell receptor signaling pathway. Expressed predominantly in lymphoid tissues such as spleen, thymus and bone marrow, TRAC-1 has been found to inhibit pathogen-induced cytokine production and down-regulates HIV replication.