Tripartite motif-containing protein 42 (TRIM42) belongs to the C-III subclass of TRIM (tripartite motif) family of proteins that are defined by their N-terminal RBCC (RING, Bbox, and coiled coil) domains, including three consecutive zinc-binding domains, a C3HC4-type RING-HC finger, Bbox1 and Bbox2, and a coiled coil domain. It also has a novel cysteine-rich motif N-terminal to the RBCC domain, as well as a COS (carboxyl-terminal subgroup one signature) box and a fibronectin type-III (FN3) domain positioned C-terminal to the RBCC domain. TRIM42 can interact with TRIM27, a known cancer-associated protein. Its precise biological function remains unclear [, ].