Semliki Forest virus non-structural protein 4 (nsP4) (SFV nsP4)

Semliki Forest virus non-structural protein 4 (nsP4) is the primary catalytic subunit of the viral replication complex, serving as the RNA-dependent RNA polymerase (RdRp) (UniProt P03315). It is essential for the synthesis of both the negative-strand RNA template and the subsequent positive-strand genomic and subgenomic RNAs required for viral progeny production (Rubach et al., 2009). Because RdRps are unique to viruses and lack direct functional homologs in human cells, nsP4 is a critical target for the development of broad-spectrum antiviral therapies. Drugs such as favipiravir and ribavirin act as nucleoside analogs that are incorporated into the growing RNA chain by nsP4, resulting in chain termination or lethal mutagenesis (Delang et al., 2014). Research into SFV nsP4 also serves as a model for understanding the replication of other medically significant alphaviruses, including Chikungunya and Eastern Equine Encephalitis viruses. The protein contains highly conserved motifs common to all RdRps, making it a focal point for structural biology and drug discovery efforts (Tomar et al., 2006).

Other names

RNA-directed RNA polymeraseRdRpP600nsP4 polymerase

Inhibition of RNA-dependent RNA polymerase activity through competitive inhibition or chain termination, leading to the suppression of viral RNA synthesis.