TRIM25, also known as estrogen responsive finger protein (EFP) is a member of the RING finger-B box-coiled coil family, and functions as a ubiquitin ligase. Mice lacking this gene displayed an underdeveloped uterus and reduced estrogen responsiveness demonstrating that this protein is essential for estrogen dependent proliferation. Expression of the gene is upregulated in response to estrogen, and it is thought to mediate estrogen actions in breast cancer as a primary response gene. The presence of potential DNA binding and dimerization transactivation domains suggests that this protein may act as a transcription factor, similar to several other members of the TRIM family. Recent reports have indicated that TRIM25 E3 ubiquitin ligase is essential for the retinoic-acid-inducible gene 1 (RIG-1) signaling pathway to elicit host antiviral innate immunity.