This article provides basic information on proteolysis involving the ubiquitin / proteasome 26S, tightly regulated process essential for the proper functioning of cells. The focus is on discussing the proteins containing the RING finger domain and function as E3 ubiquitin ligases involved in the ubiquitination of proteins destined for degradation in the proteasome. Highlighted the RING finger domain in action oligo (SCF, Parkin, VCB, APC / C) and monomer (c-Cbl, MDM2, BRCA1, CHFR, IAP) ubiquitin ligases.