Genome sequences were determined for a novel RNA virus, Leptomonas seymouri Narna-like virus 1 (LepseyNLV1). A 2.9-kb segment encodes an RNA-dependent RNA polymerase (RdRp), while a smaller 1.5-kb segment showed no database search matches. This is the first report of bisegmented Narnaviridae from insect trypanosomatids.

NS5B is pivotal RNA dependent RNA polymerase (RdRp) of HCV and NS5B function interfering halts the virus infective cycle. This work aimed to produce cell penetrable humanized single domain antibodies (SdAb; VH/V(H)H) that interfere with the RdRp activity. Recombinant NS5BΔ55 of genotype 3a HCV with de novo RNA synthetic activity was produced and used in phage biopanning for selecting phage clon...

Flavivirus methyltransferase catalyzes both guanine N7 and ribose 2'-OH methylations of the viral RNA cap (GpppA-RNA-->m(7)GpppAm-RNA). The methyltransferase is physically linked to an RNA-dependent RNA polymerase (RdRp) in the flaviviral NS5 protein. Here, we report genetic interactions of West Nile virus (WNV) methyltransferase with the RdRp and the 5'-terminal stem-loop of viral genomic RNA....

The mechanism by which viral RNA-dependent RNA polymerases (RdRp) specifically amplify viral genomes is still unclear. In the case of flaviviruses, a model has been proposed that involves the recognition of an RNA element present at the viral 5' untranslated region, stem-loop A (SLA), that serves as a promoter for NS5 polymerase binding and activity. Here, we investigated requirements for speci...

No effective therapeutic is currently in place for improved case management of severe measles or the rapid control of outbreaks. Through high-throughput screening, we recently identified a novel small-molecule class that potently blocks activity of the measles virus (MeV) RNA-dependent RNA polymerase (RdRp) complex in transient replicon assays. However, the nature of the block in RdRp activity ...

RNA viruses typically encode their own RNA-dependent RNA polymerase (RdRP) to ensure genome replication within the infected cells. RdRP function is critical not only for the virus life cycle but also for its adaptive potential. The combination of low fidelity of replication and the absence of proofreading and excision activities within the RdRPs result in high mutation frequencies that allow th...

In vitro mapping studies of the MD145 norovirus (Caliciviridae) ORF1 polyprotein identified two stable cleavage products containing the viral RNA-dependent RNA polymerase (RdRp) domains: ProPol (a precursor comprised of both the proteinase and polymerase) and Pol (the mature polymerase). The goal of this study was to identify the active form (or forms) of the norovirus polymerase. The recombina...

In addition to its role in DNA-dependent transcription, RNA polymerase II (Pol II) possesses RNA-dependent RNA polymerase (RdRP) activity (Lehmann et al, 2007). In a study published in this issue of The EMBO Journal, Wagner et al (2013) report the first native cellular function of the RdRP activity of Pol II. The authors find that a mammalian non-coding RNA (ncRNA) can serve as a template for i...

The RNA-dependent RNA polymerase (RdRp) of potato virus X (PVX) contains a glycine-lysine-serine (GKS) motif. This motif is present in the replication enzyme of many RNA viruses and is thought to be required for nucleoside triphosphate-binding. Three single amino acid changes, glycine to alanine (AKS), lysine to asparagine (GNS) and lysine to glutamate (GES) within the GKS motif of the PVX RdRp...

The rapid spread of the recent Zika virus (ZIKV) epidemic across various countries in the American continent poses a major health hazard for the unborn fetuses of pregnant women. To date, there is no effective medical intervention. The nonstructural protein 5 of Zika virus (ZIKV-NS5) is critical for ZIKV replication through the 5'-RNA capping and RNA polymerase activities present in its N-termi...