We have a number of projects in the lab to investigate the structure and function of cellular proteins that comprise the TRIM/RBCC family (about 100 different human proteins identified so far). TRIM proteins are RING-domain E3 ubiquitin ligases that regulate many different cellular processes and pathways. They appear to have particularly important roles in anti-viral defense, activation of the cellular innate immune response, inflammation, and the development of cancer. TRIMs are modular proteins with an N-terminal RING domain, followed by one or two B-box domains, a coiled-coil domain, and a C-terminal domain. The RING/B-box/coiled-coil (RBCC) or tripartite motif mediates formation of high-order assemblies. Our broad goal is to understand how TRIM assembly integrates enzymatic activity into biological function. Therefore, an important aspect of our work is to understand, by applying structural biology approaches, how these domains are arranged at the level of quaternary structure.