MOV10 is an RNA helicase that functions as a critical restriction factor against retrotransposons and viral replication through multiple mechanisms. (a) Primary function: MOV10 primarily acts as a host defense factor that restricts LINE-1 retrotransposition and inhibits viral replication, including hepatitis C virus, yellow fever virus, and hepatitis delta virus 1. It also plays essential roles in RNA-directed transcription and replication of hepatitis delta virus by interacting with small capped HDV RNAs 2. (b) Mechanism: MOV10 forms large cytoplasmic ribonucleoprotein granules with liquid-liquid phase separation properties, recruiting the decapping enzyme DCP2 to decap LINE-1 RNA, leading to RNA degradation 3. It requires both LINE-1 association through its extended motif II and granule formation via its C-terminal domain for maximal inhibitory effects 4. MOV10 also interacts with RNASEH2 to prevent formation of LINE-1 RNA-DNA hybrids during retrotransposition 5. (c) Disease relevance: MOV10 is part of the interferon-stimulated gene network and contributes to antiviral immunity 1. Its dysfunction may contribute to retrotransposon-mediated genetic instability and inflammatory diseases. (d) Clinical significance: MOV10 expression is associated with stress granule formation and has been identified as a prognostic marker in ovarian cancer 6.