RING finger, HC subclass, found in tripartite motif-containing protein 3 (TRIM3)
TRIM3, also known as brain-expressed RING finger protein (BERP), RING finger protein 97 (RNF97), or RING finger protein 22 (RNF22), is an E3 ubiquitin-protein ligase involved in the pathogenesis of various cancers. It functions as a tumor suppressor that regulates asymmetric cell division in glioblastoma. It binds to the cdk inhibitor p21(WAF1/CIP1) and regulates its availability that promotes cyclin D1-cdk4 nuclear accumulation. Moreover, TRIM3 plays an important role in the central nervous system (CNS). It corresponds to gene BERP (brain-expressed RING finger protein), a unique p53-regulated gene that modulates seizure susceptibility and GABAAR cell surface expression. Furthermore, TRIM3 mediates activity-dependent turnover of postsynaptic density (PSD) scaffold proteins GKAP/SAPAP1 and is a negative regulator of dendritic spine morphology. In addition, TRIM3 may be involved in vesicular trafficking via its association with the cytoskeleton-associated-recycling or transport (CART) complex that is necessary for efficient transferrin receptor recycling, but not for epidermal growth factor receptor (EGFR) degradation. It also regulates the motility of the kinesin superfamily protein KIF21B. TRIM3 belongs to the C-VII subclass of TRIM (tripartite motif)-NHL family that is 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, as well as a NHL (named after proteins NCL-1, HT2A and Lin-41 that contain repeats folded into a six-bladed beta propeller) repeat domain positioned C-terminal to the RBCC domain.