NS1′ Colocalizes with NS1 and Can Substitute for NS1 in West Nile Virus Replication

NS1' is a C-terminally extended form of the NS1 protein produced only by encephalitic flaviviruses from the Japanese encephalitis virus serogroup. Here we show that West Nile virus (WNV) NS1' and NS1 localize to the same cellular compartments when expressed from plasmid DNAs and also colocalize to viral RNA replication sites in infected cells. Using complementation analysis with NS1-deleted WNV cDNA, we demonstrated that NS1' is able to substitute for the crucial function of NS1 in virus replication.