RING finger, HC subclass, found in tripartite motif-containing protein 71 (TRIM71) and similar proteins
TRIM71, also known as protein lineage variant 41 (lin-41), is an E3 ubiquitin-protein ligase that may plays essential roles in embryonic stem cells, cellular reprogramming and the timing of embryonic neurogenesis. It was first identified in the nematode Caenorhabditis elegans as target of the differentiation-associated microRNA (miRNA) let-7 (lethal 7) and therefore part of a heterochronic gene network that controls larval development. In humans, it regulates let-7 microRNA biogenesis via modulation of Lin28B protein polyubiquitination. TRIM71 localizes to cytoplasmic P-bodies and directly interacts with the miRNA pathway proteins Argonaute 2 (AGO2) and DICER. It represses miRNA activity by promoting degradative ubiquitination of AGO2. Moreover, TRIM71 associates with SHCBP1, a novel component of the fibroblast growth factor (FGF) signaling pathway, and regulates its non-degradative polyubiquitination. It is also involved in the post-transcriptional regulation of the CDKN1A, RBL1 and RBL2 or EGR1 mRNAs through mediating RNA-binding in embryonic stem cells. TRIM71 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.