TRIM5 is a member of a broad family of otherwise unrelated proteins defined by the presence of a tripartite motif containing a RING domain, a B-box type 1, and a B-box type 2, followed by a coiled-coil region (1). TRIM5 has five alternately spliced isoforms, the longest of which is the ? variant which also contains a carboxy-terminal B30.2 (SPRY) domain (1). While a function has not yet been assigned to TRIM5γ, it is known that expression of TRIM5γ variants from humans, rhesus monkeys, and African green monkeys enable resistance to infection by various retroviruses including HIV-1 (2,3), albeit at differing efficiencies. Furthermore, the TRIM5γ isoform appears to serve as a scaffold for the assembly of endogenous BTBD1 and BTBD2 proteins and also exhibits autoubiquitination activity in a RING finger- and UbcH5B-dependent manner (4).Synonyms: RING finger protein 88, Tripartite motif-containing protein 5