Sequence analysis and subcellular localization of crucian carp Carassius auratus viperin

Human viperin is known as an interferon (IFN)-inducible antiviral protein and localizes to endoplasmic reticulum (ER) via its N-terminal amphipathic α-helix. Little is known about subcellular localization of fish viperin. Herein, we characterized subcellular localization of a fish viperin from crucian carp Carassius auratus. Crucian carp viperin is nearly identical to the other viperin proteins in sequence, with the exception of the first N-terminal 70 amino acids that are defined as N-terminal variable domain including an amphipathic α-helix. In addition to N-terminal variable domain, crucian carp viperin protein harbors a conserved middle radical SAM domain and a conserved C-terminal domain. Subcellular localization analyses indicate that crucian carp viperin is a cytoplasmic protein associated with ER. Sequence analyses reveal that amino acids 1-74 forms an amphipathic α-helix domain that drives ER-localization of crucian carp viperin. In addition, Coimmunoprecipitation assays show that crucian carp viperin proteins are able to self-associate. These results together indicate that similar to mammalian homologs, fish viperins likely play important roles in IFN response.