Molecular characterization of tripartite motif protein 25 (TRIM25) involved in ERα-mediated transcription in the Korean rose bitterling Rhodeus uyekii.

Tripartite motif-containing 25 (TRIM25), also known as estrogen-responsive finger protein (EFP), plays an essential role in cell proliferation and innate immunity. In the present study, we isolated and characterized the TRIM25 cDNA of the Korean rose bitterling Rhodeus uyekii, designated RuTRIM25. It encodes an open reading frame of 669 amino acids containing an N-terminal RBCC motif composed of a RING domain, two B boxes, and a coiled-coil domain and a C-terminal B30.2 (PRY/SPRY) domain. RuTRIM25 shows strong homology (79.7%) to zebrafish TRIM25 and shared 32.4-28.8% homology with TRIM25 from other species, including mammals. RuTRIM25 mRNA was expressed ubiquitously. It was highly expressed in the ovary, spleen, and liver and moderately in the stomach and intestine of normal Korean rose bitterling. The intracellular localization of RuTRIM25 in HEK293T cells was diffusely localized in the cytoplasm and its RING domain deletion mutant (RuTRIM25ΔR) was detected diffusely with some aggregates in the cytoplasm. RuTRIM25, but not RuTRIM25ΔR, is ubiquitinated in vivo. Ectopic expression of RuTRIM25 synergistically activated the estrogen receptor (ER)-mediated luciferase reporter activity in a dose-dependent manner in HEK293T cells. Together, these results suggest that the RuTRIM25 regulates the ER-mediated transcription in fish similarly to its mammalian counterpart.